THE STAR FORMATION NEWSLETTERAn electronic publication dedicated to early stellar/planetary evolution and molecular clouds

No. 257 — 10 May 2014 Editor: Bo Reipurth (reipurth@ifa.hawaii.edu)

The Star Formation Newsletter

Editor: Bo Reipurthreipurth@ifa.hawaii.edu

Technical Editor: Eli Bressertebressert@gmail.com

Technical Assistant: Hsi-Wei Yenhwyen@asiaa.sinica.edu.tw

Editorial Board

Joao AlvesAlan Boss

Jerome BouvierLee Hartmann

Thomas HenningPaul Ho

Jes JorgensenCharles J. Lada

Thijs KouwenhovenMichael R. MeyerRalph Pudritz

Luis Felipe RodrıguezEwine van Dishoeck

Hans Zinnecker

The Star Formation Newsletter is a vehicle forfast distribution of information of interest for as-tronomers working on star and planet formationand molecular clouds. You can submit materialfor the following sections: Abstracts of recentlyaccepted papers (only for papers sent to refereedjournals), Abstracts of recently accepted major re-views (not standard conference contributions), Dis-sertation Abstracts (presenting abstracts of newPh.D dissertations), Meetings (announcing meet-ings broadly of interest to the star and planet for-mation and early solar system community), NewJobs (advertising jobs specifically aimed towardspersons within the areas of the Newsletter), andShort Announcements (where you can inform or re-quest information from the community). Addition-ally, the Newsletter brings short overview articleson objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

Newsletter Archivewww.ifa.hawaii.edu/users/reipurth/newsletter.htm

List of Contents

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

My Favorite Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Abstracts of Newly Accepted Papers . . . . . . . . . . 14

Abstracts of Newly Accepted Major Reviews . 42

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

New and Upcoming Meetings . . . . . . . . . . . . . . . . . 45

New Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Passings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 49

Cover Picture

This image shows the LBN 777 nebula in Tau-rus close to the Pleiades. The cloud was origi-nally catalogued as Barnard 207, and has later be-come known as L1489. It contains the protostarIRAS 04016+2610, a small multiple system thatproduces a molecular outflow and a chain of HHobjects 360, 361, 362. The cometary shape of theglobule suggests that the star formation event mayhave been triggered by an external event.

Image courtesy Mark Hansonhttp://www.btlguce.com

Submitting your abstracts

Latex macros for submitting abstractsand dissertation abstracts (by e-mail toreipurth@ifa.hawaii.edu) are appended toeach Call for Abstracts. You can alsosubmit via the Newsletter web inter-face at http://www2.ifa.hawaii.edu/star-formation/index.cfm

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Gosta Gahmin conversation with Bo Reipurth

Q: In 1970, you were the first astronomer in Scandinaviato study young stars. From where came the inspiration?

A: It all started after my supervisor Per Olof Lindbladarranged a stay with George Herbig at the Lick Obser-vatory. George gave me a coude spectrum of RW Aur Aand suggested I should think of something one could learnfrom it. I started to read all I could find about T Tauristars (TTS) in the library. After a month we met again.I had many questions but he insisted on asking me whatI thought. He was a wonderful mentor.

When back in Stockholm after a year and half at Lick Iwas hooked on young stars, and people said I was talk-ing only about TTS during breakfast, lunch and dinner.Despite this some students thought the subject was excit-ing. A group expanded including Goran Olofsson, LennartNordh, Rene Liseau, Peter Lindroos, Malcolm Fridlund,and Erik Gullbring, some of whom are still active in as-tronomy.

Q: You have been studying RU Lupi for many years, in-cluding the first far-ultraviolet study. Does RU Lupi stillsurprise?

A: After Lick we started simultaneous spectroscopic andphotometric observations at ESO, which was still in itspioneering phase. Our first target was RU Lupi, a TTSwith an extremely rich emission line spectrum. I havereturned many times to this star as well as to RW AurA. Not unusual that astronomers return to the place ofthe crime, I have found. Each time we gained some newinsights, but new questions always popped up.

At the time new spectral windows became accessible forstudies of TTS. Observers from all parts of Europe gath-ered in Villafranca, Spain to conduct FUV observationswith the IUE satellite. I remember many exiting moments

in the control room, where people jumped and shoutedwhen they viewed the screen with spectra never seen be-fore. So did I when I saw the spectrum of RU Lupi.

We thought the strong emission lines from hot regions im-plied TTS chromospheres enhanced by factors 105 com-pared to the sun. The concept of magnetospheric accretionfrom circumstellar disks had not yet emerged. Fascinat-ing how our view of the T Tauri phenomenon has changedsince then.

And can RU Lupi still hide some secrets? Over the lastyears, my main partners on TTS have been Peter Petrov,Eric Stempels, Fred Walter, and Gregory Herczeg, andin our last paper (2013) we found evidence that the ac-cretion streams are curved and trailing the star. If con-firmed, I think an exciting step will be to match observedspectral variations with line transfer calculations based onrecent models involving complex, non-axisymmetric mag-netic field configurations.

Q: You did one of the pioneering studies of T Tauri starsin X-rays using Einstein. Do your early conclusions stillstand in light of what we have learnt from later missions?

A: After the first FUV surveys the next natural step wasto explore how TTS appear at higher energies. Timely, theX-ray satellite Einstein was launched. There were predic-tions around on high X-ray fluxes based on extrapolationsof the strong ”hot” lines found in the FUV. I selected anumber of such stars and got so astonished when I foundthat none was detected in X-rays. By chance, one field in-cluded a weak-line TTS, and yes, this object had a strongsignal. When closing a paper on this (1980) I realized thatat these relatively low X-ray energies the bulk of the X-rayemission can be absorbed in the gas surrounding the stars.I added a note on this at the last moment.

Since then X-ray observations have provided a wealth ofdata with information on stellar coronae, accretion shocks,stellar flares and also shock-excited regions further outfrom the star, like Herbig-Haro objects. I did not continuemyself within this field, except that we have collected X-ray data during periods of groundbased monitoring. It wasalways hard to arrange strictly simultaneous X-ray andoptical observations, but now we have seen such studiesappearing in the literature.

Q: You and your collaborators have found evidence thatRW Aur A may be a spectroscopic binary. Has this beenfurther supported by additional data?

A: There was indeed a time when I thought the small-amplitude periodic velocity changes we detected in TTScould flag the presence of brown dwarfs in close orbits, andwhich would eventually be swallowed by the star. It couldalso explain how non-axisymmetric accretion streams de-velop in their combined magnetospheres. I was arguingwith Petrov, who thought we instead were dealing with

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two accretion areas not aligned with the stellar rotationaxis. Colleagues called our conversations quarrels, and Iremember how we spent a whole evening in the dancinghall on a ferry between Stockholm and Helsinki totally oc-cupied by finding the weak points in each story and waysto defend our own conclusions. In fact, quarrels can bevery refreshing and creative. We finally presented bothviews in a paper on RW Aur A (2001).

Later, when investigating the same phenomenon in RULupi, I had to admit that Peter probably was on the righttrack after all. The periodic velocity changes are related tocold and hot spots on the rotating star. Usually we agreeon how to interpret observations, and our collaborationhas always survived since we met in Moscow back in 1974.

As the Swedish poet Nils Ferlin wrote: God may forgiveme certain lines. However, one must check each star care-fully. Recently, Kospal et al. found that in EX Lup suchvelocity variations are caused by a close component.

Q: You had the interesting idea to look for young binariespairing OB stars with T Tauri stars, and found a numberof such cases, work later continued by Peter Lindroos. Dothese companions appear to be normal T Tauri stars?

A: When Lindroos entered our group I had in my drawera compilation of early-type stars with faint visual compo-nent(s). A few of these secondaries were known to be oflate type. The idea was to collect Stromgren photometryand spectra for both primaries and secondaries. From thephotometry one would get the age of the systems. If thesystems were physical, also the secondaries must be veryyoung. Then their positions in the HR diagram could becompared to model tracks, and one could check for spectralcharacteristics of youth, like lithium and emission lines.

Lindroos turned on and did a very thorough survey ofsuch systems as his thesis work. He concluded that mostsystems are physical. Many secondaries populate a regionabove the main-sequence, and their strong Li line indicateyouth. Several stars show weak Hα emission. He hadlocated a population of post-T Tauri stars.

Lindroos left astronomy after his graduation. I meet himnow and then, and he was of course very pleased to knowthat the objects later were named the Lindroos stars.

Q: You and your collaborators have been studying rotatingand twisted elephant trunks in HII regions. Is this likelyto be a general phenomenon?

A: In the eighties I spent some time at the Alfven labo-ratory doing laboratory experiments shooting hot plasmainto different configurations of magnetic fields and elec-tric currents. The idea was to learn something aboutthe excitation of Herbig-Haro objects. That was fun, butmore important, I got in touch with the plasma physi-cists. They thought astronomers were neglecting electro-

magnetic forces, which was partly true. Per Carlqvist ar-gued that plasma physics should be applied in full scalein models of interstellar clouds. Even the cold molecu-lar clouds are by standard definitions plasmas. We stud-ied twisted, filamentary clouds in CO with collegues inFinland and Onsala, Anlaug Kaas and Paivi Harjunpaamapped polarization, and with Helmuth Kristen we sur-veyed elephant trunks in 10 H II regions in Hα at theNordic Optical Telescope.

We found that many trunks are composed of thin molecu-lar threads that can be confined over parsecs. Several looklike twisted coaxial cables and shaped like double helices insome cases. Not far-fetched to think that electromagneticforces play an important role in sculpting these features.Carlqvist developed the ”Theory of twisted trunks”.

Magnetic fields and electric currents are here to stay, andover the last decade some very impressive models havebeen published treating the evolution of ”magnetic” shellsand trunks in H II regions.

Q: Your latest interest are the small ”globulettes” in HIIregions. What have you learnt?

A: I always loved to be in a control room and see data ac-cumulating on-line. At NOT the trunks were seen as darksilhouettes against the nebular background on the screen.I then noticed some tiny dark spots, which I thought werebad pixels in the camera. I moved the telescope a bit, andthe spots followed the shift, they were real.

Now and then I wondered about their nature. I foundthat several people had already paid attention to similarcloudlets, for instance you Bo! Then Tiia Grenman inLulea was looking for a thesis project, and we made aninventory of tiny clouds from the NOT images in severalH II regions. We called them globulettes since they are ofa different nature than globules and proplyds, and we justpublished a survey of such objects in the Carina Nebula.We have now measured sizes and masses for more than 400globulettes. Most are of planetary mass and they have allbeen accelerated outwards from the central cluster.

I have been so happy to see an entirely new constellationof collaborators blossom, including Carina Persson at On-sala and Lauri Haikala and Minja Makela in Helsinki. Wehave now added radio and NIR observations. A question iswhether globulettes may collapse to form planetary massobjects, which will shoot into surrounding space like bul-lets. There is an enormous reservoir of free floating planetsin the Galaxy. Did some form in globulettes? Well, this isa very speculative idea, but we have discovered dense coresin many of these objects, so I think it is not impossible.

A team at UCL London has started modelling our objects.By the end of May observers and theoreticians will meetin Greece to discuss topics like this. Astronomy is fun!

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My Favorite ObjectThe Double Cluster h & χ Persei

Estelle Moraux

1 Introduction & motivation

The Perseus double cluster (02h20m, +57d08’) is the com-mon name for the two open clusters h & χ Persei (alsoknown as NGC 869 and NGC 884, respectively) in thePerseus constellation. This pair is exceptional due to thelarge number of young bright O and B stars in each cluster,and their closeness whilst still being clearly distinguished.The clusters visual magnitudes (respectively 4.9 and 5.7,Slesnick et al. 2002) make them visible to the naked eyeand a favorite of amateur astronomers. In small telescopesthe double cluster appears as a beautiful assemblage ofbright stars located in a rich star field. Dominated bybright blue stars, the clusters also host a few orange starsthat add to the visual interest (see Fig. 1).

The double cluster was first catalogued by Hipparchus(130 BC) but was probably known since antiquity. It is notclear, though, when astronomers became aware of its dou-ble nature. Claudius Ptolemy described them as a “densemass”, and Copernicus as a “nebulous star”. Tycho Brahecatalogued this object as a single star and described itas “enveloped”, “wrapped” or “enshrouded” in nebulosity.Analysing Johann Bayer’s star atlas, Uranometria 1603,partly reproduced in Fig. 2, we can realize the existenceof an h and a χ label in the sword hand of Perseus and itis thought that the double cluster represents the jeweledhandle of Perseus’s sword. It is not clear however if theh and χ in this atlas represent the same astronomical ob-jects that are today associated with the double cluster asthey are reversed to the current notation and representedwith wrong magnitudes. According to O’Meara & Green(2003), it seems that χ Persei historically correspondedto the double cluster, and very likely h Persei was a 6th

Figure 1: The Double Cluster h & χ Persei (or NGC 869and NGC 884, respectively on the right and left). Bothclusters have an apparent dimension of 30 arcmin. Copy-right Robert Gendler 2006.

magnitude star 20 arcmin west of it. Sir William Her-schel, working on the completeness of his Double StarsCatalogue, was the first astronomer to recognize h & χPersei as stellar clusters in 1780 thanks to the use of thetelescope. These are his notes when referring to χ Per-sei: “Multiple. An astonishing number of small stars allwithin the space of a few minutes. I counted not less than40 within my small field of view.”1

Figure 2: Perseus represented in Johann Bayer’s star atlas,Uranometria 1603. Note the h and χ in the sword handof Perseus. This image was retrieved from the Linda HallLibrary database online, http://lhldigital.lindahall.org/.

1Citation taken from the William Herschels Double Star Cat-alog, maintained by Bruce MacEvoy, that can be found athttp://www.handprint.com/ASTRO/herschel.html.

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h & χ Persei is the largest double cluster known nowadaysin the Milky Way. Being very dense, with a high densityof evolved high mass stars (O-B giants/ supergiants anddwarfs) it was intensively studied in the last 200 years,leading to a gradual improvement in the knowledge of itsproperties. Since early 1900, it has been the target ofextensive photometric surveys using photographic plates(e.g., van Maanen 1911; Oosterhoff 1937) and spectro-scopic studies (e.g., Trumpler 1926; Bidelman 1943; Schild1965), leading to some controversy about the distances andrelative ages of h and χ Per. More recent studies (e.g.,Keller et al. 2001; Capilla & Fabregat 2002; Slesnick et al.2002; Uribe et al. 2002; Bragg & Kenyon 2005; Mayne etal. 2007; Currie et al. 2010) are now converging to similarproperties for both clusters, with a distance modulus of∼11.8 (d ∼2.3 kpc), an extinction E(B − V ) ∼ 0.54 andan age of ∼13 Myr (Mayne & Naylor 2008). h Per is about30% more populous than χ Per with at least ∼3000 starswithin its 10 arcmin center and has an estimated mass of∼ 4700 M⊙ (Currie et al. 2010).

The age of the double cluster probes a very interestingphase for pre-main sequence evolution, and in particu-lar for stellar angular momentum evolution. By the ageof the clusters (∼ 13 Myr), the accretion disk has fullydisappeared and the stars can freely spin-up while evolv-ing towards the zero-age main sequence (ZAMS). Hence,deriving the rotational distribution of hundreds of coevallow-mass stars in this cluster allows to characterize the an-gular momentum properties of stars at the end of the ac-cretion phase, when they have finally acquired their totalmass. This was the main aim of our recent study (Morauxet al. 2013), as well as to investigate the angular momen-tum evolution of low mass stars using the distribution ofrotation rates at ∼13 Myr as initial conditions for furtherevolution to the ZAMS and onto the main sequence (MS).

2 h Persei rotational period distri-bution

Within the framework of the Monitor project (Aigrain etal. 2007), we conducted a multisite photometric moni-toring of h Persei during the fall 2008 using four differ-ent telescopes: the 3.6m Canada-France-Hawaii Telescope(CFHT), the 1.5m telescope in Maidanak (Uzbekistan),the 2.6m Shajn telescope (ZTSh) at the Crimean Astro-physical Observatory (CrAO, Ukraine), and the 2.6m tele-scope of Byurakan Observatory (Armenia). The totalamount of time spent monitoring the cluster was ∼ 110hrs, spread over two months from September 5 to Octo-ber 27, 2008. The observations were done in the I-band,and the individual exposure times were adapted to reachthe equivalent of i′CFHT ≃ 21, with a signal-to-noise ratio

larger or equal to ten at each telescope.

We then produced the light curves for each object detectedin the images of each telescope following the proceduredescribed in Irwin et al. (2007a). For the CFHT dataset,the achieved photometric precision for each data point isbetter than 2 mmag for the brightest objects (i′CFHT ≤16), with a scatter < 1 per cent up to i′CFHT ≃ 19.5. Thephotometric precision for the Maidanak data is also verygood, while for the CrAO and Byurakan photometry, thelimit for the rms scatter is around 5 mmag.

To take the best benefit of our sampling, we performedthe period search on objects detected in both CFHT andMaidanak images, which allowed us to be sensitive to pe-riodic variations on timescales of less than 0.2 day and upto 20 days. Photometry obtained at CrAO and Byurakanwas only used a posteriori to check the goodness of theperiod found. Selection of candidate members using em-pirical isochrones in various CMDs in the optical and thenear-infrared (see Fig. 3) identified 2287 objects that weredetected in both CFHT and Maidanak data. We restrictedour period analysis to these sources.

Figure 3: i′CFHT , V − i′CFHT color magnitude diagram.Left: All the objects located between the two solid lineshave been selected as possible cluster members. Right:The red open circles show the objects that have been an-alyzed, while the green crosses show the periodic objects.

The light curves of the candidate cluster members weresearched for periodic modulations due to stellar rotationusing three different methods : Lomb-Scargle periodogram(Scargle 1982; Horne & Baliunas 1986), CLEAN discreteFourier transform (CLN DFT, Roberts et al. 1987) andstring-length minimization (Dworetsky 1983). After re-moval of spurious periods resulting from the nightly sam-pling rate (frequencies around 0.5 and 1d−1), and eye

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Figure 4: Phased light curves of periodic h Per candidate members (red dots: CFHT, black dots: Maidanak). Theobject number is given in each panel (top) as well as the period (in days, bottom left) and amplitude (in magnitude,bottom right). The light curves are ordered by decreasing periodogram peak power. Only the first 21 light curves areshown here as an example.

examination of the phase folded light curves with a lowfalse alarm probability (FAP ≤ 0.05), we found 586 peri-odic objects in the mass range 0.4 ≤ M/M⊙ ≤ 1.4. Thephased light curves of 21 periodic variables are shown inFig. 4 as an example. In some cases, especially for ob-jects with short periods, the phased light curve providesclear evidence for phase and/or amplitude variations overthe time span of the observations, indicative of spot evo-lution and/or surface differential rotation over a timescaleof weeks.

As synchronized binaries are expected to have a differentangular momentum evolution than detached systems andsingle stars, we removed them from our sample to furtherinvestigate stellar rotation at 13 Myr and angular momen-tum evolution prior to the arrival on the main sequence.The obtained period distribution of h Per candidate mem-bers is shown as a function of mass in Fig. 5. It exhibits awide dispersion, with most of the measured periods in therange ∼ 0.3 to ∼ 9 days and a few slow rotators around 15days, and does not show any clear dependence on mass.In particular, the upper and lower envelopes (correspond-ing respectively to slow and fast rotators) is remarkablyflat over the whole mass range. On a log scale, the perioddistribution appears somewhat bimodal, especially at lowmasses, with a primary broad peak around 4-10 days anda secondary peak at a fraction of a day. There is also aslight indication that the 0.4-0.6 M⊙ mass objects have alarger fraction of fast rotators, which is in agreement withthe finding of previous studies (e.g., Herbst et al. 2001,Irwin et al. 2007b, 2008a, 2008b).

3 Angular momentum evolution

The derivation of hundreds of rotational periods for low-mass stars in the 13 Myr-old h Per cluster provides a newtime step to investigate pre-main sequence angular mo-mentum evolution. This time step, which was not previ-ously covered by other cluster studies (e.g., Irwin & Bou-vier 2009; Messina et al. 2010, 2011), is particularly in-teresting as it marks the end of the PMS disk accretionprocess. Disk accretion is thought to be largely terminatedby 10 Myr (Kennedy & Kenyon 2009; Fedele et al. 2010),leaving at most a few percent of stars still actively accret-ing from their disks in h Per (Currie et al. 2007). The“disk-locking process” by which stars are prevented fromspinning up during their early PMS evolution is thereforeover for most of the h Per low-mass population. Thesestars are thus expected to freely spin up as they contracttowards the ZAMS, which they eventually reach at an ageof 22, 33, 66, and 100 Myr for a mass of 1.2, 1.0, 0.7, and0.5 M⊙, respectively. The rotational distribution of h Permembers is thus particularly suited to investigate stellarspin-up at the end of PMS evolution and on the approachto the ZAMS.

Figure 6 compares the rotational distribution of h Permembers with those of solar-type and lower mass mem-bers of various open clusters over the age range from 5 to150 Myr. At all ages, a significant spread is seen in therotational period distributions.

The upper envelope of the period distribution, located at∼10 day in h Per, does not appear to evolve much between5 and 40 Myr over the mass range from 0.4 to 0.9 M⊙. Thissuggests that at least a fraction of slow rotators are pre-

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Figure 5: Periods detected for 508 h Per photometric can-didate members (excluding synchronized binaries with pe-riod ≤1d) are shown as a function of stellar mass. Periodsare plotted on a linear scale in the upper panel and on alog scale in the lower one. On the top panel, the upperx-axis scale corresponds to i′CFHT -band magnitude.

vented from spinning up over this timescale. By the ageof the Pleiades (125 Myr), the upper envelope of the dis-tribution has decreased towards faster rotation for masseslarger than 0.7 M⊙. A significant fraction of lower massstars, even at this age, still exhibits long periods, sug-gesting that the pre-ZAMS spin-up is more efficient forsolar-mass than for low-mass stars.

In contrast, the lower envelope of the period distribu-tion exhibits quite a drastic evolution from 5 Myr to theZAMS. In h Per, the lower envelope appears rather flatover the mass range 0.4-1.1 M⊙ at a period of ∼0.2-0.3d.In younger clusters, the minimum period seems to stronglydepend on mass, ranging from ∼0.4-0.5d at 0.4-0.6 M⊙ to1.0d or more for solar-type stars. This provides good evi-dence for PMS spin-up for the fast rotators between 5 and13 Myr. From 13 to 130 Myr, the fastest rotators in the0.8-1.1 M⊙ mass range have been spun down, presumablyupon their arrival on the ZAMS, while lower mass starsdown to 0.4 M⊙ still exhibit the same maximum rotationrate of ∼0.3d.

The most striking difference between the 13 Myr-old h Percluster and ZAMS clusters at an age of 125-150 Myr is the

Figure 6: Period versus mass distributions for clusterswith an age ranging from 4 to 150 Myr. The clusters’name and age are given in each panel. Red dotted lines aredrawn at periods of 0.2 and 10 days to guide the eye. Ref-erences: Cep OB3b: Littlefair et al. (2010); NGC 2362:Irwin et al. (2008a); NGC 2547: Irwin et al. (2008b);Pleiades: Hartman et al. (2010); M 50: Irwin et al.(2009); NGC 2516: Irwin et al. (2007b); M35: Meibom etal. (2009).

lack of mass dependency in the rotational distribution ofthe former, while the latter exhibit a narrow rotation-massrelationship for masses larger than about 0.7 M⊙. Indeed,the largest scatter of rotation rates over the investigatedmass range is observed for the 13 Myr-old h Per cluster,which is at the end of the PMS accretion phase. Thisresult supports the role of disk accretion in establishingthe initial dispersion of stellar angular momentum in low-mass stars (Edwards et al. 1993; Bouvier et al. 1993;Rebull et al. 2004).

While the rotational distributions of fast and slow rotatorsprovide some clues to the angular momentum evolution ofPMS stars, the complete distributions have to be modeledto understand the processes at play. We thus computedangular momentum evolution models starting from the ob-served 5 Myr rotational distributions as initial conditionsand evolved them at ages of 13, 40, and 130 Myr to com-pare with observations. The models assume all stars arereleased from their disk at 5 Myr and therefore do not in-clude any “disk-locking” process after this age. Angular

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momentum loss due to stellar winds are included in theway described in Irwin & Bouvier (2009). Core-envelopedecoupling is also included in the model through the in-troduction of a coupling timescale τc over which angularmomentum is exchanged between the radiative core andthe convective envelope (Allain 1998). Our results sug-gest that core-envelope decoupling occurs on a timescaleinversely proportional to surface rotation. Furthermore,our models indicate that less than 10% of stars may re-main coupled to their disk beyond 5 Myr in order to repro-duce the spin evolution to the ZAMS, in agreement withcurrent estimates of disk lifetimes.

4 Future work

We are now investigating the rotational period distribu-tion of χ Per using similar data obtained in 2010 to lookfor any possible difference between the two clusters. More-over, the CFHT light curves obtained in 2008 and 2010 forboth clusters will be analysed to search for period evolu-tion over a two year baseline and investigate differentialrotation.

Other clusters with an age between 10 Myr and the ZAMSare also being investigated to get further constraints on theearly stellar angular momentum evolution.

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9

Perspective

PMS Spectroscopic BinariesLisa Prato

5 Motivation

As an undergraduate I believed that few things could bemore outdated and stultifying than the study of low-massbinaries; in my mind real astronomy dealt with big, ex-plosive things, AGN, supernovae. So why do I now spenda significant fraction of my time very happily on young,low-mass spectroscopic binaries, and why are they of coreimportance to the entire field of star formation? The pri-mary virtue of a stellar binary is its adherence to simpleKeplerian motion; this makes it possible to dynamicallydetermine orbital and stellar properties with relative pre-cision. The attractive hook in the study of young spectro-scopic binaries is that they provide an unambiguous routeto the determination of T Tauri star mass ratios and inparticular masses. These properties are fundamental toour understanding of binary formation, young star evolu-tion, and the relationship between planets and their hoststars. The latter is underscored by the growing number oftransiting planets found by the Kepler mission which orbitspectroscopic binaries (e.g., Orosz et al. 2012). Althoughthere is some ambiguity as to the exact fraction of binarysystems, there is little doubt that the majority of starsreside in binary or multiple configurations. Therefore, bi-naries are integral to star formation while at the same timeproviding an invaluable tool for the measurement of fun-damental young star properties useful for anchoring the-ory to observation and thus for the characterization of theglobal young star population.

6 The Brief History of Young Spec-

troscopic Binaries

Although T Tauri stars have been studied since the 1940s(Joy 1945) and spectroscopic binaries for even longer (Pick-ering 1890), remarkably it was not until Herbig (1977)that the overlap in these two populations was noted. Inthe following decade, Mathieu et al. (1989), motivated bythe study of binary formation, began to search system-atically for the pre-main sequence (PMS) spectroscopicbinary population in Taurus. In their landmark paper,Mathieu et al. determined that short-period (P<100 days)spectroscopic binaries are likely not the drivers of circum-stellar disk dissipation in weak-lined systems, presentedorbital solutions for 5 new spectroscopic pairs, identifiedthe transition to non-zero eccentricity binaries at peri-ods of >4 days, and used the mass limits imposed by thedouble-lined spectroscopic solution for NTTS 162814−2427to test the PMS evolutionary calculations of VandenBerg(1985) and Cohen & Kuhi (1979). By the mid-1990s,Mathieu (1994) had compiled a census of 12 double-linedand 13 single-lined young spectroscopic binaries.

7 Enter the Infrared

Figure 1 shows the most recent results for the mass ra-tio distribution of double-lined PMS systems, which nownumber over 50. The obvious bias toward a mass ratio of

Figure 1: Visible light and infrared measured mass ratiosfor double-lined T Tauri spectroscopic binaries.

10

unity among the visible-light-identified pairs reflects thefact that flux scales as a steeper function of mass in thevisible than in the infrared. In the mid-1990s, Mike Simonand I began to leverage this infrared advantage on thesingle-lined systems listed in Mathieu (1994); for about90% of these binaries, colleagues, students, and I havedetermined double-lined orbits (e.g., Steffen et al. 2001;Prato et al. 2002a,b; Simon & Prato 2004; Schaefer etal. 2008; Mace et al. 2012; Simon et al. 2013; Torres etal. 2013; Karnath et al. 2013). Other sources of single-lined systems include Alcala et al. (1996, 2000), Webbet al. (1999), and Prato (2007) from which we selectedadditional targets (Mace et al. 2009; Rosero et al. 2011;Ruız-Rodrıguez et al. 2013).

Thanks to the heightened sensitivity to the secondary starspectrum achievable in the infrared, and the power of two-dimensional cross-correlation (Zucker & Mazeh 1994), ithas been possible to measure mass ratios in young sys-tems down to q = M2/M1 = 0.2. Furthermore, in col-laboration with Guillermo Torres, it has become evidentthat, once both the primary and secondary spectral typesand, perhaps more significantly, v sin i, have been esti-mated on the basis of the infrared spectra, it is possibleto then extract full double-lined solutions on the basis ofthe visible light data as well (Mace et al. 2012; Torreset al. 2013; Kellogg et al. 2014 in prep). In this waywe have been able to exploit archival visible light datafor more precise double-lined solutions. Our observed in-frared (H-band) spectral library is publicly available atwww2.lowell.edu/users/lprato/hband/homepage.html.

8 Young Star Masses

PMS stellar masses have traditionally been estimated bydetermining luminosity and effective temperature, map-ping these quantities onto the Hertzsprung-Russell (H-R)diagram, and comparing the results with models of starformation and evolution (e.g., Weinberger et al. 2013).However, models for low-mass stars suffer from the lack ofa reliable observational framework and incomplete knowl-edge of molecular opacities and diverge on the basis ofchoices for the equation of state and somewhat arbitraryinitial conditions (Baraffe et al. 2003). Figure 2 illustratesthe discrepancies between five sets of tracks for low-massstars. Ideally, a set of well-characterized young stars withmasses measured to a precision of a few % or better, span-ning the full range from ∼0.1 to ∼1.0 M⊙, and consistenteffective temperatures and luminosities, are needed.

There are two ways to dynamically measure young starmasses: (1) by mapping the Keplerian rotation of a cir-cumstellar or circumbinary disk interferometrically (e.g.,Guilloteau et al. 2013), although this approach is limited

Figure 2: Examples of scatter between 1−100 Myr agePMS mass tracks for 1.0, 0.6, and 0.1 M⊙ (Simon 2008).For the Baraffe et al. (1998, BCAH) 0.1 M⊙ track a mixinglength, α, of 1.0 was used; otherwise α = 1.9. SDF=Siesset al. (2000), PS=Palla & Stahler (1999), DM=D’Antona& Mazzitelli (1994), Yi=Yi et al. (2003).

by the requirement for an independent distance estimate,or (2) by measuring the radial velocities (RVs) of bothstars in a spectroscopic binary to obtain the orbital pe-riod, eccentricity, time of periastron passage, longitude ofperiastron, and component velocity semi-amplitudes (P,T, e, ω, K1, and K2) combined with the inclination, i,measurable in an angularly resolved visual binary (e.g.,Schaefer et al. 2008) or in an eclipsing system (e.g., Stas-sun et al. 2004):

M1 =1.036× 10−7(K1 +K2)

2K2P (1− e2)3/2

sin3iM⊙ (1)

M2 =1.036× 10−7(K1 +K2)

2K1P (1− e2)3/2

sin3iM⊙ (2)

where K1 and K2 are in km s−1 and P is in days.

The observational challenge is to identify young binarieswith sufficiently short periods that we can determine theirdouble-lined spectroscopic solution while at the same timeangularly resolving the components via adaptive opticsimaging, non-redundant masking, and interferometry, orto identify young binaries in eclipsing systems. To date,there are only about a dozen pairs with components of <1 M⊙ and sufficiently precise (better than 10%), dynami-cally determined absolute masses adequate for the calibra-tion of the low-mass theoretical models (e.g., Hillenbrand& White 2004; G. Schaefer, priv. comm.). The good news

11

is that some of our recent observational results (e.g., Tor-res et al. 2013; Schaefer et al. 2012; Simon et al. 2013;Le Bouquin et al. 2013) have provided a few more preciseanchor points and are spurring theorists to revisit thesestellar models (I. Baraffe, priv. comm.). We are inchingour way toward a substantial sample of precise, absolute,young star masses.

There are, of course, undiscussed challenges in placingspectroscopic binary components, even those with pre-cisely measured masses, on an H-R diagram (!). One ofthe foremost is the determination of Teff , and anotherthe determination of luminosity, or absolute magnitude,which require a relatively precise knowledge of the dis-tance to the system. M. Simon and others are attackingthe issue of Teff and the exquisite work of R. Torres, L.Loinard, and colleagues (e.g., Torres et al. 2009), not tomention the GAIA results at the end of its 5-year missionin 2018, address the distances to young stars in nearbyregions. Also, for an angularly resolved visual binary thatis also a double-lined spectroscopic binary, distance maybe directly determined (Schaefer et al. 2008).

9 Mass Ratio and Other Distribu-tions

Dynamically measured mass ratios number <5 dozen (Fig-ure 1). Most stars in the Solar neighborhood reside inbinary or multiple systems, yet we do not yet have a sat-isfactory picture of how they form, especially the shortestperiod, i.e. spectroscopic binary, systems. Theory hasreached a point where simulations of the formation of en-tire clusters of young stars yield mass ratio distributionsfor sub-samples of various primary star masses (e.g., Bate2012). Unhappily, there are no analogous observed youngstar mass ratio distributions for comparison. Clearly farlarger observed samples are needed to guide further theo-retical developments.

Identifying spectroscopic binaries is a time-consuming pro-cess requiring at least two and preferably at least threeepochs of observations (e.g., Prato 2007; Furesz et al.2008; Tobin et al. 2009). Orbital solutions with betterthan 10% uncertainties in the elements require a dozen,or better a couple of dozen, observations distributed inphase. The beauty of a mass ratio measurement is that,unlike the other orbital properties, it is possible to obtainwith as few as three observations following Wilson (1941),illustrated in Figure 3. To test how robust a mass ratiomeasurement is on the basis of three pairs of radial ve-locities, we conducted an experiment using a system forwhich numerous radial velocity pairs were available. Thethirteen pairs of primary and secondary radial velocitiesfor the young spectroscopic binary RX J1622.7-2325Nw

shown in Figure 3 (mass ratio is 0.98 and center of massvelocity, γ, is −6.78 km s−1; Rosero et al. 2011) werecombined in all 286 possible combinations of three andthe mass ratio calculated using the negative of the slopeof the primary versus secondary RV (Wilson 1941) for eachset of 3 radial velocities. A Gaussian fit to the resultinghistogram showed that mass ratio determinations basedon three radial velocity observations are strongly peakedat 0.98 with a FWHM spread of only 0.08 in mass ratio, il-lustrating the reliability of the approach (V. Rosero, priv.comm.).

Figure 3: Linear fit to the primary vs. secondary radialvelocities for RX J1622.7-2325Nw (Rosero et al. 2011).Uncertainties in the RV are not shown because they aresmaller than the symbol size (1−2 km s−1).

With the acquisition of a large sample of double-lined spec-troscopic binaries (preferably hundreds!), complete withinindividual star forming regions, broad areas of heretoforeunexamined study will open up. Spectroscopic binaryproperties will facilitate a new perspective on star forma-tion.

These properties include:• The total frequency of spectroscopic binaries in a givenregion• The frequency of spectroscopic binaries as a function ofprimary star mass (or spectral type)• The mass ratio distribution of spectroscopic binaries• The period distribution of spectroscopic binaries• The eccentricity distribution of spectroscopic binaries

Some questions that will be possible to explore:• How do short-period spectroscopic binaries form? Dothey dynamically evolve and if so how quickly?• How do circumstellar and circumbinary disks form and

12

evolve in such systems? (There is ample evidence forboth!)• Do global parameters such as the mass ratio distributionvary between star forming regions?• What do the spectroscopic binary population propertiestell us about a star forming region? About angular mo-mentum in star forming regions?• What are the relationships between mass, Teff , and lu-minosity for T Tauri stars of a given age?• What is the eccentricity vs. log period distribution forcoeval populations of spectroscopic binaries? Can this beused effectively as a stellar chronometer?

10 How Do We Get There

Complete surveys for spectroscopic binaries in the nearbystar forming regions are necessary but have never beencarried out given the intensive observing required. An ex-cellent approach taken by Furesz et al. (2008) and Tobinet al. (2009) leveraged the multiplexing advantage of theHectochelle instrument at the MMT. With over 200 fibersdistributable over a degree of sky at once, Hectochelle(Szentgyorgyi et al. 2011) is ideal for the observation ofmany stars simultaneously in dense star forming regionssuch as Orion and NGC 2264. With adequate integrationtime and hence sufficiently high signal to noise ratios, com-plete surveys are within reach over the next few years withsuch a facility. Furthermore, many, if not most, stars insmaller regions, such as Taurus and Ophiuchus, have beenobserved at high spectral resolution repeatedly and theirspectroscopic binary status is determinable. Thus, com-pleting full surveys of, for example, Taurus, Ophiuchus,Orion, Scorpius, IC 348, and NGC 2264 over the nextdecade is not an unreasonable goal in the campaign toidentify unknown spectroscopic binaries.

As for characterization of such systems, infrared spec-troscopy at 2 to 4-meter class telescopes provides a prac-tical if time-consuming approach. Such a strategy mightprovide key projects for such mid-sized facilities. With theUniversity of Texas/KASI IR spectrograph, IGRINS (Yuket al. 2010), currently in commissioning, on the McDon-ald Observatory 2.7-meter, or on the Lowell Observatory4.3-meter telescope, tremendous progress could be madeto these ends. Other possibilities include the Phoenixspectrograph on the KPNO 4-meter and CSHELL or itsreplacement, iSHELL, on the NASA IRTF 3-meter tele-scope.

With a significant sample of spectroscopic binary orbitaldata in place, the astrometric GAIA mission is poised toexplode the number of precise young star masses withinour reach. By intensive mapping of spectroscopic binaryorbits via motion of the binary photocenter, with some

careful analysis the results of the complete GAIA missionwill reveal the orbital inclinations. In combination withEquations (1) and (2) this will yield masses for systemswith periods down to a few days at distances of out to ∼1kpc. It’s an excellent time to be in the young spectroscopicbinary business!

11 Acknowledgements

This manuscript benefitted from comments on the partof my colleagues most involved in this work with me,Gail Schaefer, Guillermo Torres, and Michal Simon. For-mer students Gregory Mace, Viviana Rosero, Dary Ruız-Rodrıguez, and Nicole Karnath, and colleague LawrenceWasserman have all contributed significantly to the effortsdescribed here.

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Alcala, J. M., et al. 2000, A&A, 353, 186Alcala, J. M., et al. 1996, A&AS, 119, 7Baraffe, I., et al. 1998, A&A, 337, 403Baraffe, I., et al. 2003, A&A, 402, 701Bate, M. R. 2012, MNRAS, 419, 3115Cohen, M., & Kuhi, L. V. 1979, ApJS, 41, 743D’Antona, F., & Mazzitelli, I. 1994, ApJS, 90, 467Furesz, G., et al. 2008, ApJ, 676, 1109Guilloteau, S., et al. 2013, A&A, 549, 92Herbig, G. H. 1977, ApJ, 214, 747Hillenbrand, L. A., & White, R. J. 2004, ApJ, 604, 741Joy, A. H. 1945, ApJ, 102, 168Karnath, N., et al. 2013, AJ, 146, 149Le Bouquin, J.-B., et al. A&A, 561, 101Mace, G. N., et al. 2009, AJ, 137, 3487Mace, G. N., et al. 2012, AJ, 144, 55Mathieu, R. D., et al. 1989, AJ, 98, 987Mathieu, R. D. 1994, ARAA, 32, 465Orosz, J. A., et al. 2012, Science, 337, 1511Palla, F., & Stahler, S. W. 1999, ApJ, 525, 772Pickering, E. C. 1890, MNRAS, 50, 296Prato, L., et al. 2002a, ApJ, 569, 863Prato, L., et al. 2002b, ApJ, 579, L99Prato, L. 2007, ApJ, 657, 338Rosero, V., et al. 2011, AJ, 141, 13Ruız-Rodrıguez, D., et al. 2013, AJ, 145, 162Schaefer, G. H., et al. 2008, AJ, 135, 1659Schaefer, G. H., et al. 2012, ApJ, 756, 120Siess, L., et al. 2000, A&A, 358, 593Simon, M., & Prato, L. 2004, ApJ, 613, L69Simon, M. 2008, The Power of Optical/IR Interferometry, 227Simon, M., et al. 2013, ApJ, 773, 28Stassun, K. G., et al. 2004, ApJS, 151, 357Steffen, A., et al. 2001, AJ, 122, 997Szentgyorgyi, A., et al. 2011, PASP, 123, 1188Tobin, J. J., et al. 2009, ApJ, 697, 1103Torres, G., et al. 2013, ApJ, 773, 40Torres, R. M., et al. 2009, ApJ, 698, 242VandenBerg, D. A. 1985, ApJS, 58, 561Webb, R. A., et al. 1999, ApJ, 512, L63Weinberger, A. J., et al. 2013, ApJ, 762, 118Wilson, O. C. 1941, ApJ, 93, 29Yi, S. K., et al. 2003, ApJS, 144, 259Zucker, S., & Mazeh, T. 1994, ApJ, 420, 806

13

Abstracts of recently accepted papers

Large-scale magnetic fields in Bok globules

Gesa Bertrang1, Sebastian Wolf1 and Himadri S. Das2

1 University of Kiel, Institute of Theoretical Physics and Astrophysics, Leibnizstr. 15, 24118 Kiel, Germany2 Assam University, Department of Physics, Silchar – 788 011, India

E-mail contact: gbertrang at astrophysik.uni-kiel.de

Context: The role of magnetic fields in the star formation process is a contentious matter of debate. In particular, noclear observational proof exists of a general influence by magnetic fields during the initial collapse of molecular clouds.Aims: Our aim is to examine magnetic fields and their influence on a wide range of spatial scales in low-mass star-forming regions.Method: We trace the large-scale magnetic field structure on scales of 103 − 105 AU in the local environment of Bokglobules through optical and near-infrared polarimetry and combine these measurements with existing submillimetermeasurements, thereby characterizing the small-scale magnetic field structure on scales of 102 − 103 AU.Results: For the first time, we present polarimetric observations in the optical and near-infrared of the three Bokglobules B335, CB68, and CB54, combined with archival observations in the submillimeter and the optical. We find asignificant polarization signal (P > 2 %, P/σP > 3) in the optical and near-infrared for all three globules. Additionally,we detect a connection between the structure on scales of 102 − 103 AU to 103 − 104 AU for both B335 and CB68.Furthermore, for CB54, we trace ordered polarization vectors on scales of ∼ 105 AU. We determine a magnetic fieldorientation that is aligned with the CO outflow in the case of CB54, but nearly perpendicular to the CO outflow forCB68. For B335 we find a change in the magnetic field oriented toward the outflow direction, from the inner core tothe outer regions.Conclusion: We find strongly aligned polarization vectors that indicate dominant magnetic fields on a wide range ofspatial scales.

Accepted by A&A

http://www.aanda.org/articles/aa/pdf/forth/aa23091-13.pdf

Planetesimal driven migration as an explanation for observations of high levels of warm,exozodiacal dust

Amy Bonsor1,2, Sean N. Raymond3,4, Jean-Charles Augereau1, and Chris W. Ormel5

1 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno-ble, F-38041, France2 School of Physics, H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK3 CNRS, UMR 5804, Laboratoire d’Astrophysique de Bordeaux, 2 rue de l’Observatoire, BP 89, F-33271 FloiracCedex, France4 Universite de Bordeaux, Observatoire Aquitain des Sciences de l’Univers, 2 rue de l’Observatoire, BP 89, F-33271Floirac Cedex, France5 Astronomy Department, University of California, Berkeley, CA 94720, USA

E-mail contact: amy.bonsor at gmail.com

High levels of exozodiacal dust have been observed in the inner regions of a large fraction of main sequence stars. Giventhe short lifetime of the observed small dust grains, these ‘exozodis’ are difficult to explain, especially for old (>100Myr) stars. The exozodiacal dust may be observed as excess emission in the mid-infrared, or using interferometry. Wehypothesise that exozodi are sustained by planetesimals scattered by planets inwards from an outer planetesimal belt,where collision timescales are long. In this work, we use N-body simulations to show that the outwards migration of aplanet into a belt, driven by the scattering of planetesimals, can increase, or sustain, the rate at which planetesimals

14

are scattered from the outer belt to the exozodi region. We hypothesise that this increase is sufficient to sustain theobserved exozodi on Gyr timescales. No correlation between observations of an outer belt and an exozodi is requiredfor this scenario to work, as the outer belt may be too faint to detect. If planetesimal driven migration does explainthe observed exozodi, this work suggests that the presence of an exozodi indicates the presence of outer planets anda planetesimal belt.

Accepted by MNRAS

http://arxiv.org/pdf/1404.2606

Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-Lived Ra-dioisotopes with a Shock Wave. III. Rotating Three Dimensional Cloud Cores

A. P. Boss1 and S. A. Keiser1

1 DTM, Carnegie Institution, 5241 Broad Branch Road, NW, Washington, DC 20015-1305, USA

E-mail contact: aboss at carnegiescience.edu

A key test of the supernova triggering and injection hypothesis for the origin of the solar system’s short-lived radioiso-topes is to reproduce the inferred initial abundances of these isotopes. We present here the most detailed models todate of the shock wave triggering and injection process, where shock waves with varied properties strike fully threedimensional, rotating, dense cloud cores. The models are calculated with the FLASH adaptive mesh hydrodynamicscode. Three different outcomes can result: triggered collapse leading to fragmentation into a multiple protostar system;triggered collapse leading to a single protostar embedded in a protostellar disk; or failure to undergo dynamic collapse.Shock wave material is injected into the collapsing clouds through Rayleigh-Taylor fingers, resulting in initially inho-mogeneous distributions in the protostars and protostellar disks. Cloud rotation about an axis aligned with the shockpropagation direction does not increase the injection efficiency appreciably, as the shock parameters were chosen tobe optimal for injection even in the absence of rotation. For a shock wave from a core-collapse supernova, the dilutionfactors for supernova material are in the range of ∼ 10−4 to ∼ 3×10−4, in agreement with recent laboratory estimatesof the required amount of dilution for 60Fe and 26Al. We conclude that a type II supernova remains as a promisingcandidate for synthesizing the solar system’s short-lived radioisotopes shortly before their injection into the presolarcloud core by the supernova’s remnant shock wave.

Accepted by ApJ

http://home.dtm.ciw.edu/users/boss/ftp/triggerIII.pdf

http://arxiv.org/pdf/1404.7190

Temperaments of young stars: rapid mass-accretion rate changes in T Tauri and HerbigAe stars

Grainne Costigan1,2,3, Jorick S. Vink2, Aleks Scholz1,4, Tom Ray1 and Leonardo Testi3,5

1 Dublin Institute for Advanced Studies, Ireland2 Armagh Observatory, Northern Ireland3 European Southern Observatory, Germany4 School of Physics & Astronomy, University of St. Andrews, Scotland5 INAF-Osservatorio Astrofisico di Arcetri, Italy; Excellence Cluster Universe, Germany

E-mail contact: costigag at gmail.com

Variability in emission lines is a characteristic feature in young stars and can be used as a tool to study the physicsof the accretion process. Here we present a study of Hα variability in 15 T Tauri and Herbig Ae stars (K7 - B2) overa wide range of time windows, from minutes, to hours, to days, and years. We assess the variability using linewidthmeasurements and the time series of line profiles. All objects show gradual, slow profile changes on time-scales ofdays. In addition, in three cases there is evidence for rapid variations in Hα with typical time-scales of 10min, whichoccurs in 10% of the total covered observing time. The mean accretion-rate changes, inferred from the line fluxes,are0.01 - 0.07dex for time-scales of < 1 hour, 0.04 - 0.4 dex for time-scales of days, and 0.13 - 0.52dex for time-scales ofyears.In Costigan et al. (2012) we derived an upper limit finding that the intermediate (days) variability dominated over

15

longer (years) variability. Here our new results, based on much higher cadence observations, also provide a lower limitto accretion-rate variability on similar time-scales (days), thereby constraining the accretion rate variability physics ina much more definitive way. A plausible explanation for the gradual variations over days is an asymmetric accretionflow resulting in a rotational modulation of the accretion-related emission, although other interpretations are possibleas well. In conjunction with our previous work, we find that the time-scales and the extent of the variability is similarfor objects ranging in mass from ∼ 0.1 to ∼5M⊙. This confirms that a single mode of accretion is at work from TTauri to Herbig Ae stars – across a wide range of stellar masses.

Accepted by MNRAS

http://adsabs.harvard.edu/pdf/2014arXiv1403.4088C

A First-Look Atmospheric Modeling Study of the Young Directly-Imaged Planet-MassCompanion, ROXs 42Bb

Thayne Currie1, Adam Burrows2, and Sebastian Daemgen1

1 Department of Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, ON, Canada2 Department of Astrophysical Sciences, Princeton University, USA

E-mail contact: tcurrie at cfa.harvard.edu

We present and analyze JKsL′ photometry and our previously published H-band photometry and K-band spec-

troscopy for ROXs 42Bb, an object Currie et al. (2014) first reported as a young directly imaged planet-mass com-panion. ROXs 42Bb exhibits IR colors redder than field L dwarfs but consistent with other planet-mass companions.From the H2O-2 spectral index, we estimate a spectral type of L0 ± 1; weak detections/non-detections of the CObandheads, Na I, and Ca I support evidence for a young, low surface gravity object primarily derived from the H2(K)index. ROXs 42Bb’s photometry/K-band spectrum are inconsistent with limiting cases of dust-free atmospheres(COND) and marginally inconsistent with the AMES/DUSTY models and the BT-SETTL models. However, ROXS42Bb data are simultaneously fit by atmosphere models incorporating several micron-sized dust grains entrained inthick clouds, although further modifications are needed to better reproduce the K-band spectral shape. ROXs 42Bb’sbest-estimated temperature is Teff ∼ 1950–2000 K, near the low end of the empirically-derived range in Currie etal. (2014). For an age of ∼ 1–3 Myr and considering the lifetime of the protostar phase, ROXs 42Bb’s luminosity oflog(L/L⊙) ∼ −3.07± 0.07 implies a mass of 9+3

−3 MJ, making it one of the lightest planetary mass objects yet imaged.

Accepted by ApJ

http://arxiv.org/pdf/1404.0131

Molecular Gas Clumps from the Destruction of Icy Bodies in the β Pictoris Debris Disk

W.R.F. Dent1, M. C. Wyatt2, A. Roberge3, J.-C. Augereau4, S. Casassus5, S. Corder1, J.S. Greaves6,

I. de Gregorio-Monsalvo1, A. Hales1, A.P. Jackson2, A. Meredith Hughes7, A.-M. Lagrange4, B.

Matthews8, and D. Wilner9

1 ALMA Santiago Central Offices, Alonso de Cordova 3107, Vitacura, Casilla 763 0355, Santiago, Chile2 Institute of Astronomy Madingley Road, Cambridge CB3 0HA, UK3 Exoplanets and Stellar Astrophysics Lab, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA4 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG), UMR 5274, Greno-ble, F-38041, France5 Departamento de Astronomıa, Universidad de Chile, Casilla 36-D, Santiago, Chile6 Dept. of Astronomy, University of St. Andrews, North Haugh, St. Andrews, UK7 Wesleyan University Department of Astronomy, Van Vleck Observatory, 96 Foss Hill Drive, Middletown, CT 06459,USA8 National Research Council of Canada, Herzberg Astronomy & Astrophysics Programs, 5701 West Saanich Road,Victoria, BC, Canada, V9E 2E7, and Department of Physics & Astronomy, University of Victoria, Finnerty Road,Victoria, BC, V8P 5C2, Canada9 Smithsonian Astrophysical Observatory, 60 Garden St., MS 42, Cambridge, MA 02138 USA

E-mail contact: wdent at alma.cl

16

Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets.But is gas also released in such events? Observations at submm wavelengths of the archetypal debris disk around βPictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highlyasymmetric, with 30% found in a single clump 85 AU from the star, in a plane closely aligned with the orbit of theinner planet, β Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonancewith an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

Accepted by Science

http://arxiv.org/pdf/1404.1380

GG Tau: the fifth element

E. Di Folco1,2, A. Dutrey1,2, J.-B. Le Bouquin3, S. Lacour4, J.-P. Berger5, R. Kohler6, S. Guilloteau1,2,

V. Pietu7, J. Bary8, T. Beck9, H. Beust3, and E. Pantin10

1 Univ. Bordeaux, Laboratoire d’Astrophysique de Bordeaux, UMR 5804, F-33270, Floirac, France2 CNRS, LAB, UMR 5804, F-33270 Floirac, France3 UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble UMR 5274, F-38041, Greno-ble, France4 LESIA, CNRS/UMR-8109, Observatoire de Paris, UPMC, Universite Paris Diderot, 5 place J. Janssen, F-92195,Meudon, France5 European Southern Observatory, D-85748, Garching by Munchen, Germany6 Max-Planck-Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany7 IRAM, 300 rue de la piscine, F-38406 Saint-Martin d’Heres, France8 Department of Physics and Astronomy, Colgate University, 13 Oak Drive, Hamilton, NY 13346, USA9 Space Telescope Science Institute, 3700 San Martin Dr. Baltimore, MD 21218, USA10 Laboratoire AIM, CEA/DSM - CNRS - Universit Paris Diderot, IRFU/SAP, F-91191, Gif-sur-Yvette, France

E-mail contact: emmanuel.difolco at obs.u-bordeaux1.fr

We aim at unveiling the observational imprint of physical mechanisms that govern planetary formation in young,multiple systems. In particular, we investigate the impact of tidal truncation on the inner circumstellar disks. Weobserved the emblematic system GG Tau at high-angular resolution: a hierarchical quadruple system composed oflow-mass T Tauri binary stars surrounded by a well-studied, massive circumbinary disk in Keplerian rotation. We usedthe near-IR 4-telescope combiner PIONIER on the VLTI and sparse-aperture-masking techniques on VLT/NaCo toprobe this proto-planetary system at sub-AU scales. We report the discovery of a significant closure-phase signal in Hand Ks bands that can be reproduced with an additional low-mass companion orbiting GG Tau Ab, at a (projected)separation ρ = 31.7 ± 0.2 mas (4.4 au) and PA = 219.6 ± 0.3. This finding offers a simple explanation for severalkey questions in this system, including the missing-stellar-mass problem and the asymmetry of continuum emissionfrom the inner dust disks observed at millimeter wavelengths. Composed of now five co-eval stars with 0.02 ≤ M∗ ≤0.7 M⊙, the quintuple system GG Tau has become an ideal test case to constrain stellar evolution models at youngages (few 106 yr).

Accepted by A&A

http://arxiv.org/pdf/1404.2205

Characterizing the structure of diffuse emission in Hi-GAL maps

D. Elia1, F. Strafella2, N. Schneider3, R. Paladini4, R. Vavrek5, Y. Maruccia2, S. Molinari1, S. Pezzuto1,

A. Noriega-Crespo6,5, K.L.J. Rygl7, A.M. Di Giorgio1, A. Traficante8, E. Schisano4, L. Calzoletti9, M.

Pestalozzi1, S.J. Liu1, P. Natoli10,11,9,12, M. Huang13, P. Martin14, Y. Fukui15 and T. Hayakawa15

1 IAPS-INAF, Via Fosso del Cavaliere 100, 00133 Roma, Italy2 Dipartimento di Matematica e Fisica, Universit del Salento, CP 193, 73100 Lecce, Italy3 Univ. Bordeaux, LAB, CNRS, UMR 5804, 33270, Floirac, France4 Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA5 Herschel Science Centre, European Space Astronomy Centre, Villafranca del Castillo. Apartado de Correos 78,

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28080 Madrid, Spain6 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA7 Research and Scientific Support Department, European Space Agency (ESA-ESTEC), PO Box 299, 2200 AG,Noordwijk, The Netherlands8 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M139PL, UK9 Agenzia Spaziale Italiana Science Data Center, c/o ESRIN, via Galileo Galilei, 00044 Frascati, Italy10 Dipartimento di Fisica e Science della Terra, Universit di Ferrara Via Saragat, 1, 44100 Ferrara, Italy11 INFN, Sezione di Ferrara, via Saragat 1, 44100 Ferrara, Italy12 INAF-IASF Bologna, Via P. Gobetti 101, 40129, Bologna13 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China14 Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S3H8, Canada15 Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan

E-mail contact: davide.elia at iaps.inaf.it

We present a study of the structure of the Galactic interstellar medium through the Delta-variance technique, relatedto the power spectrum and the fractal properties of infrared/sub-mm maps. Through this method, it is possibleto provide quantitative parameters which are useful to characterize different morphological and physical conditions,and to better constrain the theoretical models. In this respect, the Herschel Infrared Galactic Plane Survey carriedout at five photometric bands from 70 to 500 µm constitutes an unique database for applying statistical tools to avariety of regions across the Milky Way. In this paper, we derive a robust estimate of the power-law portion of thepower spectrum of four contiguous 2 × 2 Hi-GAL tiles located in the third Galactic quadrant (217 < ℓ < 225,−2 < b < 0). The low level of confusion along the line of sight testified by CO observations makes this region an idealcase. We find very different values of the power spectrum slope from tile to tile but also from wavelength to wavelength(2 < β < 3), with similarities between fields attributable to components located at the same distance. Thanks to thecomparison with models of turbulence, an explanation of the determined slopes in terms of the fractal geometry isalso provided, and possible relations with the underlying physics are investigated. In particular, an anti-correlationbetween ISM fractal dimension and star formation efficiency is found for the two main distance components observedin these fields. A possible link between the fractal properties of the diffuse emission and the resulting clump massfunction is discussed.

Accepted by The Astrophysical Journal

http://arxiv.org/pdf/1404.2285v1.pdf

An Optical Spectroscopic Study of T Tauri Stars. I. Photospheric Properties

Gregory J. Herczeg1 and Lynne A. Hillenbrand2

1 Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, HaiDian Qu, Beijing 100871,China2 Caltech, 1200 East California Blvd, Pasadena, CA 91125, USA

E-mail contact: gherczeg1 at gmail.com

Estimates of the mass and age of young stars from their location in the HR diagram are limited by not only thetypical observational uncertainties that apply to field stars, but also by large systematic uncertainties related tocircumstellar phenomena. In this paper, we analyze flux calibrated optical spectra to measure accurate spectral typesand extinctions of 283 nearby T Tauri stars. The primary advances in this paper are (1) the incorporation of asimplistic accretion continuum in optical spectral type and extinction measurements calculated over the full opticalwavelength range and (2) the uniform analysis of a large sample of stars. Comparisons between the non-accretingTTS photospheric templates and stellar photosphere models are used to derive conversions from spectral type totemperature. Differences between spectral types can be subtle and difficult to discern, especially when accountingfor accretion and extinction. The spectral types measured here are mostly consistent with spectral types measuredover the past decade. However, our new spectral types are 1-2 subclasses later than literature spectral types for theoriginal members of the TWA and are discrepant with literature values for some well known Taurus CTTSs. Ourextinction measurements are consistent with other optical extinction measurements but are typically 1 mag lower than

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nIR measurements, likely the result of methodological differences and the presence of nIR excesses in most CTTSs.As an illustration of the impact of accretion, SpT, and extinction uncertainties on the HR diagrams of young clusters,we find that the resulting luminosity spread of stars in the TWA is 15-30%. The luminosity spread in the TWA andpreviously measured for binary stars in Taurus suggests that for a majority of stars, protostellar accretion rates arenot large enough to significantly alter the subsequent evolution.

Accepted by ApJ

http://xxx.lanl.gov/pdf/1403.1675

Protoplanetary dust porosity and FU Orionis Outbursts: Solving the mystery of Earth’smissing volatiles

Alexander Hubbard1 and Denton S. Ebel2

1 Department of Astrophysics, American Museum of Natural History, New York,NY 10024-5192, USA2 Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY 10024-5192,USA

E-mail contact: ahubbard at amnh.org

The Earth is known to be depleted in volatile lithophile elements in a fashion that defies easy explanation. We resolvethis anomaly with a model that combines the porosity of collisionally grown dust grains in protoplanetary disks withheating from FU Orionis events that dramatically raise protoplanetary disk temperatures. The heating from an FUOrionis event alters the aerodynamical properties of the dust while evaporating the volatiles. This causes the dustto settle, abandoning those volatiles. The success of this model in explaining the elemental composition of the Earthis a strong argument in favor of highly porous collisionally grown dust grains in protoplanetary disks outside ourSolar System. Further, it demonstrates how thermal (or condensation based) alterations of dust porosity, and henceaerodynamics, can be a strong factor in planet formation, leading to the onset of rapid gravitational instabilities inthe dust disk and the subsequent collapse that forms planetesimals.

Accepted by Icarus

http://arxiv.org/pdf/1404.3995

TADPOL: A 1.3mm Survey of Dust Polarization in Star-forming Cores and Regions

Charles L. H. Hull1, Richard L. Plambeck1, Woojin Kwon13, Geoffrey C. Bower1,18, John M. Carpenter2,

Richard M. Crutcher4, Jason D. Fiege9, Erica Franzmann9, Nicholas S. Hakobian4, Carl Heiles1, Mar-

tin Houde10,3, A. Meredith Hughes14, James W. Lamb2, Leslie W. Looney4, Daniel P. Marrone15,

Brenda C. Matthews11,12, Thushara Pillai2, Marc W. Pound5, Nurur Rahman16, Goran Sandell8,

Ian W. Stephens4,17, John J. Tobin7, John E. Vaillancourt8, N. H. Volgenau6, and Melvyn C. H. Wright1

1 Astronomy Department & Radio Astronomy Laboratory, University of California, Berkeley, CA 94720-3411, USA2 Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA91125, USA3 Division of Physics, Mathematics, & Astronomy, California Institute of Technology, Pasadena, CA 91125, USA4 Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green Street, Urbana, IL 61801,USA5 Astronomy Department & Laboratory for Millimeter-wave Astronomy, University of Maryland, College Park, MD20742, USA6 Combined Array for Research in Millimeter-wave Astronomy, Owens Valley Radio Observatory, P.O. Box 968, BigPine, CA 93513, USA7 National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA8 SOFIA Science Center, Universities Space Research Association, NASA Ames Research Center, Moffett Field, CA94035, USA9 Department of Physics & Astronomy, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada10 Department of Physics & Astronomy, University of Western Ontario, London, ON, N6A 3K7, Canada11 Department of Physics & Astronomy, University of Victoria, 3800 Finnerty Rd., Victoria, BC, V8P 5C2, Canada

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12 National Research Council of Canada, 5071 West Saanich Rd., Victoria, BC, V9E 2E7, Canada13 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands14 Van Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459,USA15 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA16 Physics Department, University of Johannesburg, C1-Lab 140, PO Box 524, Auckland Park 2006, South Africa17 Institute for Astrophysical Research, Boston University, Boston, MA 02215, USA18 ASIAA, 645 N. A’ohoku Place, Hilo, HI, 96720, USA

E-mail contact: chat at astro.berkeley.edu

We present λ 1.3mm CARMA observations of dust polarization toward 30 star-forming cores and 8 star-forming regionsfrom the TADPOL survey. We show maps of all sources, and compare the ∼ 2.5′′ resolution TADPOL maps with∼ 20′′ resolution polarization maps from single-dish submillimeter telescopes. Here we do not attempt to interpretthe detailed B-field morphology of each object. Rather, we use average B-field orientations to derive conclusions in astatistical sense from the ensemble of sources, bearing in mind that these average orientations can be quite uncertain.We discuss three main findings: (1) A subset of the sources have consistent magnetic field (B-field) orientations betweenlarge (∼ 20′′) and small (∼ 2.5′′) scales. Those same sources also tend to have higher fractional polarizations thanthe sources with inconsistent large-to-small-scale fields. We interpret this to mean that in at least some cases B-fieldsplay a role in regulating the infall of material all the way down to the ∼ 1000AU scales of protostellar envelopes. (2)Outflows appear to be randomly aligned with B-fields; although, in sources with low polarization fractions there is ahint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fieldshave been wrapped up by envelope rotation. (3) Finally, even at ∼ 2.5′′ resolution we see the so-called “polarizationhole” effect, where the fractional polarization drops significantly near the total intensity peak. All data are publiclyavailable in the electronic edition of this article.

Accepted by the Astrophysical Journal Supplement

Subarcsecond Imaging of the NGC 6334 I(N) Protocluster: Two Dozen Compact Sourcesand a Massive Disk Candidate

T. R. Hunter1, C. L. Brogan1, C. J. Cyganowski2,3 and K. H. Young2

1 National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA2 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA3 SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, UK

E-mail contact: thunter at nrao.edu

Using the SMA and VLA, we have imaged the massive protocluster NGC 6334 I(N) at high angular resolution(0.5′′ ∼ 650 AU) from 6 cm to 0.87 mm, detecting 18 new compact continuum sources. Three of the new sources arecoincident with previously-identified H2O masers. Together with the previously-known sources, these data bring thenumber of likely protocluster members to 25 for a protostellar density of ∼ 700 pc−3. Our preliminary measurementof the Q-parameter of the minimum spanning tree is 0.82 – close to the value for a uniform volume distribution.All of the (nine) sources with detections at multiple frequencies have SEDs consistent with dust emission, and two(SMA 1b and SMA 4) also have long wavelength emission consistent with a central hypercompact HII region. Thermalspectral line emission, including CH3CN, is detected in six sources: LTE model fitting of CH3CN (J=12–11) yieldstemperatures of 72–373 K, confirming the presence of multiple hot cores. The fitted LSR velocities range from −3.3to −7.0 km s−1, with an unbiased mean square deviation of 2.05 km s−1, implying a protocluster dynamical mass of410±260 M⊙. From analysis of a wide range of hot core molecules, the kinematics of SMA 1b are consistent with arotating, infalling Keplerian disk of diameter 800 AU and enclosed mass of 10-30 M⊙ that is perpendicular (within 1)to the large-scale bipolar outflow axis. A companion to SMA 1b at a projected separation of 0.45′′ (590 AU; SMA 1d),which shows no evidence of spectral line emission, is also confirmed. Finally, we detect one 218.4400 GHz and several229.7588 GHz Class-I CH3OH masers.

Accepted by The Astrophysical Journal

http://www.cv.nrao.edu/~thunter/papers/ngc6334in2014.pdf

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A long-term UBVRI photometric study of the pre-main sequence star V350 Cep

Sunay Ibryamov1, Evgeni Semkov1 and Stoyanka Peneva1

1 Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, BG-1784 Sofia,Bulgaria

E-mail contact: sibryamov at astro.bas.bg

Results from UBVRI optical photometric observations of the pre-main sequence star V350 Cep during the period2004-2014 are presented in the paper. The star is discovered in 1977 due to the remarkable increase in brightnesswith more than 5 mag (R). In the previous studies V350 Cep is considered a potential member of the groups of FUorsor EXors eruptive variables. Our data suggest that during the period of observations the star keeps its maximumbrightness with low amplitude photometric variations. Our conclusion is that V350 Cep is probably an intermediateobject between FUors and EXors, similar to V1647 Ori.

Accepted by Research in Astronomy and Astrophysics

http://arxiv.org/pdf/1404.5902

The effect of starspots on the radii of low-mass pre-main sequence stars

R.J. Jackson1 and R.D. Jeffries1

1 Astrophysics Group, Research Institute for the Environment, Physical Sciences and Applied Mathematics, KeeleUniversity, Keele, Staffordshire ST5 5BG, UK

E-mail contact: r.d.jeffries at keele.ac.uk

A polytropic model is used to investigate the effects of dark photospheric spots on the evolution and radii of mag-netically active, low-mass (M < 0.5 M⊙), pre-main sequence (PMS) stars. Spots slow the contraction along Hayashitracks and inflate the radii of PMS stars by a factor of (1−β)−N compared to unspotted stars of the same luminosity,where β is the equivalent covering fraction of dark starspots and N ≃ 0.45 ± 0.05. This is a much stronger inflationthan predicted by the models of Spruit & Weiss (1986) for main sequence stars with the same beta, where N ∼ 0.2–0.3.These models have been compared to radii determined for very magnetically active K- and M-dwarfs in the youngPleiades and NGC 2516 clusters, and the radii of tidally-locked, low-mass eclipsing binary components. The binarycomponents and ZAMS K-dwarfs have radii inflated by ∼ 10 per cent compared to an empirical radius-luminosityrelation that is defined by magnetically inactive field dwarfs with interferometrically measured radii; low-mass M-typePMS stars, that are still on their Hayashi tracks, are inflated by up to ∼ 40 per cent. If this were attributable tostarspots alone, we estimate that an effective spot coverage of 0.35 < β < 0.51 is required. Alternatively, global inhi-bition of convective flux transport by dynamo-generated fields may play a role. However, we find greater consistencywith the starspot models when comparing the loci of active young stars and inactive field stars in colour-magnitudediagrams, particularly for the highly inflated PMS stars, where the large, uniform temperature reduction required inglobally inhibited convection models would cause the stars to be much redder than observed.

Accepted by MNRAS

http://arxiv.org/pdf/1404.0683

Searching for circumplanetary disks around LkCa 15

Andrea Isella1, Claire J. Chandler2, John M. Carpenter1, Laura M. Perez2, and Luca Ricci1

1 Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA2 National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA

E-mail contact: isella at astro.caltech.edu

We present Karl G. Jansky Very Large Array (VLA) observations of the 7 mm continuum emission from the disksurrounding the young star LkCa 15. The observations achieve an angular resolution of 70 mas and spatially resolvethe circumstellar emission on a spatial scale of 9 AU. The continuum emission traces a dusty annulus of 45 AU inradius that is consistent with the dust morphology observed at shorter wavelengths. The VLA observations also reveala compact source at the center of the disk, possibly due to thermal emission from hot dust or ionized gas located

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within a few AU from the central star. No emission is observed between the star and the dusty ring, and, in particular,at the position of the candidate protoplanet LkCa 15 b. By comparing the observations with theoretical models forcircumplanetary disk emission, we find that if LkCa 15 b is a massive planet (>5 MJ) accreting at a rate greaterthan 10−6 MJ yr−1, then its circumplanetary disk is less massive than 0.1 MJ, or smaller than 0.4 Hill radii. Similarconstraints are derived for any possible circumplanetary disk orbiting within 45 AU from the central star. The massestimate are uncertain by at least one order of magnitude due to the uncertainties on the mass opacity. Future ALMAobservations of this system might be able to detect circumplanetary disks down to a mass of 5 × 10−4 MJ and assmall as 0.2 AU, providing crucial constraints on the presence of giant planets in the act of forming around this youngstar.

Accepted by ApJ

http://arxiv.org/pdf/1404.5627

Detectability of Glycine in Solar-type System Precursors

Izaskun Jimenez-Serra1, Leonardo Testi1, Paola Caselli2,3 and Serena Viti4

1 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany2 School of Physics & Astronomy, University of Leeds, LS2 9JT, Leeds, UK3 Max-Planck-Institute for Extraterrestrial Physics (MPE), Giessenbachstr., 85741 Garching, Germany4 Department of Physics & Astronomy, University College London, Gower Place, WC1E 6BT, London, UK

E-mail contact: ijimenez at eso.org

Glycine (NH2CH2COOH) is the simplest amino acid relevant for life. Its detection in the interstellar medium iskey to understand the formation mechanisms of pre-biotic molecules and their subsequent delivery onto planetarysystems. Glycine has extensively been searched for toward hot molecular cores, although these studies did not yieldany firm detection. In contrast to hot cores, low-mass star forming regions, and in particular their earliest stagesrepresented by cold pre-stellar cores, may be better suited for the detection of glycine as well as more relevant forthe study of pre-biotic chemistry in young Solar System analogs. We present 1D spherically symmetric radiativetransfer calculations of the glycine emission expected to arise from the low-mass pre-stellar core L1544. Water vapourhas recently been reported toward this core, indicating that a small fraction of the grain mantles in L1544 (∼0.5%)has been injected into the gas phase. Assuming that glycine is photo-desorbed together with water in L1544, andconsidering a solid abundance of glycine on ices of ∼10−4 with respect to water, our calculations reveal that severalglycine lines between 67GHz and 80GHz have peak intensities larger than 10mK. These results show for the firsttime that glycine could reach detectable levels in cold objects such as L1544. This opens up the possibility to detectglycine, and other pre-biotic species, at the coldest and earliest stages in the formation of Solar-type systems withnear-future instrumentation such as the Band 2 receivers of ALMA.

Accepted by Astrophysical Journal Letters

http://arxiv.org/pdf/1404.5849

Unfolding the Laws of Star Formation: The Density Distribution of Molecular Clouds

Jouni Kainulainen1, Christoph Federrath2, and Thomas Henning1

1 Max-Planck-Institute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany2 Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800, Australia

E-mail contact: jtkainul at mpia.de

The formation of stars shapes the structure and evolution of entire galaxies. The rate and efficiency of this processare affected substantially by the density structure of the individual molecular clouds in which stars form. The mostfundamental measure of this structure is the probability density function of volume densities (ρ-PDF), which determinesthe star formation rates predicted with analytical models. This function has remained unconstrained by observations.We have developed an approach to quantify ρ-PDFs and establish their relation to star formation. The ρ-PDFsinstigate a density threshold of star formation and allow us to quantify the star formation efficiency above it. Theρ-PDFs provide new constraints for star formation theories and correctly predict several key properties of the star-forming interstellar medium.

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Accepted by Science

http://arxiv.org/pdf/1404.2722

Herschel evidence for disk flattening or gas depletion in transitional disks

J.T. Keane1, I. Pascucci1, C. Espaillat2, P. Woitke3, S. Andrews4, I. Kamp5, W.-F. Thi6, G. Meeus7,

and W.R.F. Dent8

1 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA2 Department of Astronomy, Boston University, Boston, MA 02215, USA3 SUPA, School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK4 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA5 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands6 Universite Joseph Fourier Grenoble-1, CNRS-INSU, Institut de Planetologie et d’Astrophysique (IPAG) UMR 5274,38041 Grenoble, France7 Universidad Autonoma de Madrid, Dpt. Fisica Teorica, Campus Cantoblanco, 28049 Madrid, Spain8 ALMA SCO, Alonso de Cordova 3107, Vitacura, Santiago, Chile

E-mail contact: jkeane at lpl.arizona.edu

Transitional disks are protoplanetary disks characterized by reduced near- and mid-infrared emission with respectto full disks. This characteristic spectral energy distribution indicates the presence of an optically thin inner cavitywithin the dust disk believed to mark the disappearance of the primordial massive disk. We present new HerschelSpace Observatory PACS spectra of [OI] 63 µm for 21 transitional disks. Our survey complements the larger HerschelGASPS program “Gas in Protoplanetary Systems” (Dent et al. 2013) by quadrupling the number of transitional disksobserved with PACS at this wavelength. [OI] 63 µm traces material in the outer regions of the disk, beyond the innercavity of most transitional disks. We find that transitional disks have [OI] 63 µm line luminosities two times fainterthan their full disk counterparts. We self consistently determine various stellar properties (e.g. bolometric luminosity,FUV excess, etc.) and disk properties (e.g. disk dust mass, etc.) that could influence the [OI] 63 µm line luminosityand we find no correlations that can explain the lower [OI] 63 µm line luminosities in transitional disks. Using a gridof thermo-chemical protoplanetary disk models, we conclude that either transitional disks are less flared than full disksor they possess lower gas-to-dust ratios due to a depletion of gas mass. This result suggests that transitional disks aremore evolved than their full disk counterparts, possibly even at large radii.

Accepted by ApJ

http://arxiv.org/pdf/1404.0709

Rolling friction of adhesive microspheres

S. Krijt1, C. Dominik2,3 and A.G.G.M. Tielens1

1 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands2 Astronomical Institute ’Anton Pannekoek’, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, TheNetherlands3 Afdeling Sterrenkunde, Radboud Universiteit Nijmegen, Postbus 9010, 6500 GL, Nijmegen, The Netherlands

E-mail contact: krijt at strw.leidenuniv.nl

The rolling friction of adhesive microspheres is an important quantity as it determines the strength and stability oflarger aggregates. Current models predict rolling forces that are 1 to 2 orders of magnitude smaller than observedexperimentally. Starting from the well-known Johnson-Kendall-Roberts (JKR) contact description, we derive ananalytical theory for the rolling friction based on the concept of adhesion hysteresis, e.g. a difference in apparentsurface energies for opening/closing cracks. We show how adhesion hysteresis causes the pressure distribution withinthe contact to become asymmetrical, leading to an opposing torque. Analytical expressions are derived relating thesize of the hysteresis, the rolling torque, and the rolling displacement, ξ. We confirm the existence of a critical rollingdisplacement for the onset of rolling, the size of which is set by the amount of adhesion hysteresis and the size of thecontact area. We demonstrate how the developed theory is able to explain the large rolling forces and particle-sizedependence observed experimentally. Good agreement with experimental results is achieved for adhesion hysteresis

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values of (∆γ/γ) ≃ 3 for polystyrene, and (∆γ/γ) ≃ 0.5 for silicates, at crack propagation rates of 0.1µm s−1 and1− 10µm s−1 respectively.

Accepted by Journal of Physics D: Applied Physics

http://iopscience.iop.org/0022-3727/47/17/175302/

The Dependence of Protostellar Luminosity on Environment in the Cygnus-X Star-Forming Complex

E. Kryukova1, S. T. Megeath1, J. L. Hora2, R. A. Gutermuth3, S. Bontemps4,5, K. Kraemer6, M.

Hennemann7, N. Schneider4,5, Howard A. Smith2 and F. Motte7

1 Ritter Astrophysical Observatory, Department of Physics and Astronomy, University of Toledo, Toledo, OH, USA2 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA3 Department of Astronomy, University of Massachusetts, Amherst, MA, USA4 Univ. Bordeaux, LAB, UMR 5804, F-33270, Floirac, France5 CNRS, LAB, UMR 5804, F-33270, Floirac, France6 Institute for Scientific Research, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA7 Laboratoire AIM, CEA/IRFU - CNRS/INSU - Universite Paris Diderot, Service d’Astrophysique, Bat. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France

E-mail contact: tommegeath at gmail.com

The Cygnus-X star-forming complex is one of the most active regions of low and high mass star formation within 2kpc of the Sun. Using mid-infrared photometry from the IRAC and MIPS Spitzer Cygnus-X Legacy Survey, we haveidentified over 1800 protostar candidates. We compare the protostellar luminosity functions of two regions withinCygnus-X: CygX-South and CygX-North. These two clouds show distinctly different morphologies suggestive ofdissimilar star-forming environments. We find the luminosity functions of these two regions are statistically different.Furthermore, we compare the luminosity functions of protostars found in regions of high and low stellar density withinCygnus-X and find that the luminosity function in regions of high stellar density is biased to higher luminosities. Intotal, these observations provide further evidence that the luminosities of protostars depend on their natal environment.We discuss the implications this dependence has for the star formation process.

Accepted by Astronomical Journal

Main article at: http://astro1.physics.utoledo.edu/~megeath/cygnus_x/ms_final.pdf

Data table at: http://astro1.physics.utoledo.edu/~megeath/cygnus_x/photometry_table.pdf

Stellar dynamics in gas: The role of gas damping

Nathan W.C. Leigh1,2, Alessandra Mastrobuono Battisti3, Hagai B. Perets3,4, and Torsten Boker5

1 Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB T6G 2E1, Canada2 Department of Astrophysics, American Museum of Natural History, Central Park West and 79th Street, New York,NY 10024, USA3 Physics Department, Technion: Israel Institute of Technology, Haifa, Israel 320004 Deloro Fellow5 European Space Agency, Space Science Department, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands

E-mail contact: nleigh at ualberta.ca

In this paper, we consider how gas damping affects the dynamical evolution of gas-embedded star clusters. Using asimple three-component (i.e. one gas and two stellar components) model, we compare the rates of mass segregationdue to two-body relaxation, accretion from the interstellar medium, and gas dynamical friction in both the supersonicand subsonic regimes. Using observational data in the literature, we apply our analytic predictions to two differentastrophysical environments, namely galactic nuclei and young open star clusters. Our analytic results are then testedusing numerical simulations performed with the NBSymple code, modified by an additional deceleration term to modelthe damping effects of the gas.The results of our simulations are in reasonable agreement with our analytic predictions, and demonstrate that gas

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damping can significantly accelerate the rate of mass segregation. A stable state of approximate energy equilibriumcannot be achieved in our model if gas damping is present, even if Spitzer’s Criterion is satisfied. This instabilitydrives the continued dynamical decoupling and subsequent ejection (and/or collisions) of the more massive population.Unlike two-body relaxation, gas damping causes overall cluster contraction, reducing both the core and half-mass radii.If the cluster is mass segregated (and/or the gas density is highest at the cluster centre), the latter contracts fasterthan the former, accelerating the rate of core collapse.

Accepted by MNRAS

http://arxiv.org/pdf/1404.0379

Herschel-Planck dust optical-depth and column-density maps: I. Method descriptionand results for Orion

Marco Lombardi1,4, Herve Bouy2, Joao Alves3, and Charles J. Lada4

1 University of Milan, Department of Physics, via Celoria 16, I-20133 Milan, Italy2 Centro de Astrobiologıa, INTA-CSIC, PO Box 78, 28691 Villanueva de la Canada, Madrid, Spain3 University of Vienna, Turkenschanzstrasse 17, 1180 Vienna, Austria4 Harvard-Smithsonian Center for Astrophysics, Mail Stop 72, 60 Garden Street, Cambridge, MA 02138

E-mail contact: marco.lombardi at unimi.it

We present high-resolution, high dynamic range column-density and color-temperature maps of the Orion complexusing a combination of Planck dust-emission maps, Herschel dust-emission maps, and 2MASS NIR dust-extinctionmaps. The column-density maps combine the robustness of the 2MASS NIR extinction maps with the resolution andcoverage of the Herschel and Planck dust-emission maps and constitute the highest dynamic range column-densitymaps ever constructed for the entire Orion complex, covering 0.01 mag < AK < 30 mag, or 2 × 1020 cm−2 < N <5 × 1023 cm−2. We determined the ratio of the 2.2 µm extinction coefficient to the 850 µm opacity and found thatthe values obtained for both Orion A and B are significantly lower than the predictions of standard dust models, butagree with newer models that incorporate icy silicate-graphite conglomerates for the grain population. We show thatthe cloud projected pdf, over a large range of column densities, can be well fitted by a simple power law. Moreover,we considered the local Schmidt-law for star formation, and confirm earlier results, showing that the protostar surfacedensity Σ∗ follows a simple law Σ∗ ∝ Σβ

gas, with β ∼ 2.

Accepted by A&A

http://arxiv.org/pdf/1404.0032

Mapping of interstellar clouds with infrared light scattered from dust: TMC-1N

J. Malinen1, M. Juvela1, V.-M. Pelkonen2,1, and M.G. Rawlings3

1 Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland2 Finnish Centre for Astronomy with ESO, University of Turku, Vaisalantie 20, FI-21500 Piikkio, Finland3 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA

E-mail contact: johanna.malinen at helsinki

Mapping of near-infrared (NIR) scattered light is a recent method for the study of interstellar clouds, complementingother, more commonly used methods, like dust emission and extinction. Our goal is to study the usability of thismethod on larger scale, and compare the properties of a filament using NIR scattering and other methods. We alsostudy the radiation field and differences in grain emissivity between diffuse and dense areas. We have used scatteredJ , H , and K band surface brightness WFCAM-observations to map filament TMC-1N in Taurus, covering an area of1 × 1 corresponding to ∼ (2.44 pc)2. We have converted the data into optical depth and compared the results withNIR extinction and Herschel observations of submm dust emission. We see the filament in scattered light in all threeNIR bands. We note that our WFCAM observations in TMC-1N show notably lower intensity than previous resultsin Corona Australis using the same method. We show that 3D radiative transfer simulations predict similar scatteredsurface brightness levels as seen in the observations. However, changing the assumptions about the background canchange the results of simulations notably. We derive emissivity by using optical depth in the J band as an independenttracer of column density. We obtain opacity σ(250 µm) values 1.7–2.4 × 10−25 cm2/H, depending on assumptions of

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the extinction curve, which can change the results by over 40%. These values are twice as high as obtained for diffuseareas, at the lower limit of earlier results for denser areas. We show that NIR scattering can be a valuable tool inmaking high resolution maps. We conclude, however, that NIR scattering observations can be complicated, as thedata can show relatively low-level artefacts. This suggests caution when planning and interpreting the observations.

Accepted by A&A

http://arxiv.org/pdf/1404.2539

On the steady state collisional evolution of debris disks around M dwarfs

Etienne Morey1and Jean-Francois Lestrade2

1 Observatoire de Paris - LERMA, 61 Av. de l’Observatoire, F-75014, Paris, France2 Observatoire de Paris - LERMA, CNRS, 61 Av. de l’Observatoire, F-75014, Paris, France

E-mail contact: jean-francois.lestrade at obspm.fr

Debris disks have been found primarily around intermediate and solar mass stars (spectral types A–K), but rarelyaround low-mass M-type stars. This scarcity of detections in M star surveys can be confronted with the predictionsof the steady state collisional evolution model. First, we determine the parameters of the disk population evolvedwith this model and fit to the distribution of the fractional dust luminosities measured in the surveys of A- andFGK-type stars observed by the infrared satellite Spitzer. Thus, in our approach, we stipulate that the initial diskmass distribution is bimodal and that only high-mass collisionally-dominated disks are detected. The best determinedparameter is the diameter Dc of the largest planetesimals in the collisional cascade of the model, which ranges between2 and 60 km, consistently for disks around A- and FGK-type stars. Second, we assume that the same disk populationsurrounds the M dwarfs that have been the subjects of debris disk searches in the far-infrared with Spitzer and atsubmillimeter wavelengths with radiotelescopes. We find, in the framework of our study, that this disk population,which has been fit to the AFGK data, is still consistent with the observed lack of disks around M dwarfs with Spitzer.

Accepted by A&A

http://arxiv.org/pdf/1404.1954

A multiple system of high-mass YSOs surrounded by disks in NGC7538 IRS1:Gas Dynamics on Scales 10–700 AU from CH3OH Maser and NH3 Thermal Lines

Luca Moscadelli1 and Ciriaco Goddi2

1 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy2 Joint Institute for VLBI in Europe, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands

E-mail contact: goddi at jive.nl

NGC7538 IRS1 is claimed to be a high-mass young stellar object (YSO) with 30 M⊙, surrounded by a rotatingKeplerian-disk, probed by a linear distribution of methanol masers. The YSO is also powering a strong compact HII region and an ionized wind, and is driving at least one molecular outflow. The axes orientations of the differentstructures (ionized gas, outflow, and disk) are however misaligned with each other, which led to different competingmodels proposed to explain individual structures. We investigate the 3D kinematics and dynamics of circumstellar gaswith very high linear resolution, from tens to 1500 AU, with the ultimate goal of building a comprehensive dynamicalmodel for what is considered the best high-mass accretion disk candidate around an O-type young star in the northernhemisphere. We use high-angular resolution observations of 6.7 GHz CH3OH masers with the EVN, NH3 inversionlines with the JVLA B-Array, and radio continuum with the VLA A-Array. In particular, we employed four differentobserving epochs of EVN data at 6.7 GHz, spanning almost eight years, which enabled us to measure, besides line-of-sight (l.o.s.) velocities and positions (as done in previous works), also l.o.s. accelerations and proper motions ofCH3OH masers. In addition, we imaged highly-excited NH3 inversion lines, from (6,6) to (13,13), which enabled usto probe the hottest molecular gas very close to the exciting source(s). We confirm previous results that five 6.7 GHzmaser clusters (labeled from ”A” to ”E”) are distributed over a region extended N–S across ≈1500 AU, and areassociated with three components of the radio continuum emission. We propose that these maser clusters identifythree individual high-mass YSOs in NGC7538 IRS1, named IRS1a (associated with clusters ”B” and ”C”), IRS1b(associated with cluster ”A”), and IRS1c (associated with cluster ”E”). We model the masers in both clusters ”A” and

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”B”+”C” in terms of an edge-on disk in centrifugal equilibrium. Based on our modeling, masers of clusters ”B”+”C”may trace a quasi-Keplerian ∼1 M⊙, thin disk, orbiting around a high-mass YSO, IRS1a, of up to ≈25 M⊙. ThisYSO dominates the bolometric luminosity of the region. The disk traced by the masers of cluster ”A” is both massive(<∼16 M⊙ inside a radius of ≈500 AU) and thick (opening angle ≈ 45), and the mass of the central YSO, IRS1b, isconstrained to be at most a few M⊙. Towards cluster ”E”, NH3 and 6.7 GHz masers trace more quiescent dynamicsthan for the other clusters. The presence of a radio continuum peak suggests that the YSO associated with thecluster ”E”, IRS1c, may be an ionizing, massive YSO as well. The presence of a multiple system of high-mass YSOsnaturally explains all the different orientations and disk/outflow structures proposed for the region in previous models.

Accepted by Astronomy & Astrophysics

http://arxiv.org/pdf/1404.3957

The formation of the W43 complex: constraining its atomic-to-molecular transition andsearching for colliding clouds

Frederique Motte1, Q. Nguyen Luong2, N. Schneider3, F. Heitsch4, S. Glover5, P. Carlhoff6, T. Hill7,

S. Bontemps3, P. Schilke6, F. Louvet1, M. Hennemann8, P. Didelon1 and H. Beuther8

1 Laboratoire AIM Paris-Saclay, CEA/IRFU - CNRS/INSU - Universite Paris Diderot, Service d’Astrophysique, Bat.709, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex, France2 Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8,Canada3 OASU/LAB-UMR 5804, CNRS/INSU - Universite Bordeaux 1, 2 rue de l’Observatoire, BP 89, F-33270 Floirac,France4 Department of Physics and Astronomy, University of North Carolina Chapel Hill, Phillips Hall, Chapel Hill, NC27599-3255, USA5 Universitat Heidelberg, Zentrum fur Astronomie, Institut fur Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120Heidelberg, Germany6 Physikalisches Institut, Universitat zu Koln, Zulpicher Str. 77, D-50937 Koln, Germany7 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile8 Max-Planck-Institut fur Astronomie, Konigsstuhl 17, 69117 Heidelberg, Germany

E-mail contact: frederique.motte at cea.fr

Numerical simulations have explored the possibility to form molecular clouds through either a quasi-static, self-gravitating mechanism or the collision of gas streams or lower-density clouds. They also quantitatively predict thedistribution of matter at the transition from atomic to molecular gases. We aim to observationally test these models bystudying the environment of W43, a molecular cloud complex recently identified near the tip of the Galactic long bar.Using Galaxy-wide HI and 12CO 1–0 surveys we searched for gas flowing toward the W43 molecular cloud complex.We also estimated the HI and H2 mass surface densities to constrain the transition from atomic to molecular gasaround and within W43. We found three cloud ensembles within the position-velocity diagrams of 12CO and HI gases.They are separated by ∼20 km s−1 along the line of sight and extend into the 13CO velocity structure of W43. Sincetheir velocity gradients are consistent with free-fall, they could be nearby clouds attracted by, and streaming toward,the W43 ∼107 M⊙ potential well. We show that the HI surface density, ΣHI = 45− 85 M⊙,pc

−2, does not reach anythreshold level but increases when entering the 130 pc-wide molecular complex previously defined. This suggests thatan equilibrium between H2 formation and photodissociation has not yet been reached. The H2-to-HI ratio measuredover the W43 region and its surroundings, RH2

∼ 3.5±32, is high, indicating that most of the gas is already in molecular

form in W43 and in structures several hundreds of parsecs downstream along the Scutum-Centaurus arm. The W43molecular cloud complex may have formed, and in fact may still be accreting mass from the agglomeration of clouds.Already in the molecular-dominated regime, most of these clouds are streaming from the Scutum-Centaurus arm. Thisis in clear disagreement with quasi-static and steady-state models of molecular cloud formation.

Accepted by Astronomy & Astrophysics

http://arxiv.org/pdf/1404.4404

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Spatial differences between stars and brown dwarfs: a dynamical origin?

Richard J. Parker1,2 and Morten Andersen3

1 Astrophysics Research Institute, Liverpool John Moores University, IC2 Liverpool Science Park, 146 Brownlow Hill,Liverpool, L3 5RF, UK2 Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093, Zurich, Switzerland3 Institut de Planetologie et d’Astrophysique de Grenoble, BP 53, F-38041 Grenoble Cedex 9, France

E-mail contact: R.J.Parker at ljmu.ac.uk

We use N -body simulations to compare the evolution of spatial distributions of stars and brown dwarfs in youngstar-forming regions. We use three different diagnostics; the ratio of stars to brown dwarfs as a function of distancefrom the region’s centre, RSSR, the local surface density of stars compared to brown dwarfs, ΣLDR, and we compare theglobal spatial distributions using the ΛMSR method. From a suite of twenty initially statistically identical simulations,6/20 attain RSSR << 1 and ΣLDR << 1 and ΛMSR << 1, indicating that dynamical interactions could be responsiblefor observed differences in the spatial distributions of stars and brown dwarfs in star-forming regions. However, manysimulations also display apparently contradictory results - for example, in some cases the brown dwarfs have muchlower local densities than stars (ΣLDR << 1), but their global spatial distributions are indistinguishable (ΛMSR = 1)and the relative proportion of stars and brown dwarfs remains constant across the region (RSSR = 1). Our resultssuggest that extreme caution should be exercised when interpreting any observed difference in the spatial distributionof stars and brown dwarfs, and that a much larger observational sample of regions/clusters (with complete massfunctions) is necessary to investigate whether or not brown dwarfs form through similar mechanisms to stars.

Accepted by MNRAS

http://arxiv.org/pdf/1403.7053

Collective outflow from a small multiple stellar system

Thomas Peters1, Pamela D. Klaassen2, Mordecai-Mark Mac Low3,4, Martin Schron4,5, Christoph

Federrath6, Michael D. Smith7 and Ralf S. Klessen4

1 Institut fur Theoretische Physik, Universitat Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland2 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands3 Dept. of Astrophysics, American Museum of Natural History, 79th Street at Central Park West, New York, USA4 Zentrum fur Astronomie der Universitat Heidelberg, Institut fur Theoretische Astrophysik, Albert-Ueberle-Str. 2,D-69120 Heidelberg, Germany5 Dept. of Computational Hydrosystems, Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15,D-04318 Leipzig, Germany6 Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800, Australia7 Centre for Astrophysics & Space Science, University of Kent, Canterbury, CT2 7NH, England

E-mail contact: tpeters at physik.uzh.ch

The formation of high-mass stars is usually accompanied by powerful protostellar outflows. Such high-mass outflowsare not simply scaled-up versions of their lower-mass counterparts, since observations suggest that the collimationdegree degrades with stellar mass. Theoretically, the origins of massive outflows remain open to question becauseradiative feedback and fragmentation of the accretion flow around the most massive stars, with M > 15 M⊙, mayimpede the driving of magnetic disk winds. We here present a three-dimensional simulation of the early stages of corefragmentation and massive star formation that includes a subgrid-scale model for protostellar outflows. We find thatstars that form in a common accretion flow tend to have aligned outflow axes, so that the individual jets of multiplestars can combine to form a collective outflow. We compare our simulation to observations with synthetic H2 and COobservations and find that the morphology and kinematics of such a collective outflow resembles some observed massiveoutflows, such as Cepheus A and DR 21. We finally compare physical quantities derived from simulated observationsof our models to the actual values in the models to examine the reliability of standard methods for deriving physicalquantities, demonstrating that those methods indeed recover the actual values to within a factor of 2–3.

Accepted by ApJ

http://arxiv.org/pdf/1404.5463

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The Origin of Ionized Filaments Within the Orion-Eridanus Superbubble

Andy Pon1,2,3, Doug Johnstone4,3,2, John Bally5, and Carl Heiles6

1 School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK2 Department of Physics and Astronomy, University of Victoria, PO Box 3055 STN CSC, Victoria BC V8W 3P6,Canada3 NRC-Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada4 Joint Astronomy Centre, 660 North Aohoku Place, University Park, Hilo, HI 96720, USA5 Department of Astrophysical and Planetary Sciences, University of Colorado, UCB 389 CASA, Boulder, CO 80389-0389, USA6 Astronomy Department, University of California, 601 Campbell Hall 3411, Berkeley, CA 94720-3411, USA

E-mail contact: phyapon at leeds.ac.uk

The Orion-Eridanus superbubble, formed by the nearby Orion high mass star-forming region, contains multiple brightHα filaments on the Eridanus side of the superbubble. We examine the implications of the Hα brightnesses and sizesof these filaments, the Eridanus filaments. We find that either the filaments must be highly elongated along the lineof sight or they cannot be equilibrium structures illuminated solely by the Orion star-forming region. The Eridanusfilaments may, instead, have formed when the Orion-Eridanus superbubble encountered and compressed a pre-existing,ionized gas cloud, such that the filaments are now out of equilibrium and slowly recombining.

Accepted by MNRAS

http://arxiv.org/pdf/1404.1917

Imaging polarimetry of the rotating Bok globule CB67

M.S. Prokopjeva1, A.K. Sen2,3, V.B. Il’in1,4,5, N.V. Voshchinnikov1, and R. Gupta2

1 St. Petersburg State University, Astronomical Institute Universitetskij pr. 28, St.Petersburg, 198504, Russia2 Inter University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune 411007, India3 Assam University, Silchar, 788011 India4 Main (Pulkovo) Astronomical Observatory, Pulkovskoe sh. 65/1, St.Petersburg, 196140, Russia5 St. Petersburg State University of Aerospace Instrumentation, ul. Bolshaya Morskaya 67, St.Petersburg, 190000,Russia

E-mail contact: ari-76 at yandex.ru

Polarimetric observations of about 50 stars located in a close vicinity of the Bok globule CB67 having significantlynonspherical shape and rapid rotation are performed. The data obtained are compared with the available observationsof this globule at radio and submillimeter wavelengths as well as some theoretical calculations. It is found that theelongation and the rotation moment of CB67 are oriented rather perpendicular to the magnetic fields, which is unusualfor Bok globules and is difficult to be explained from the theoretical point of view.

Accepted by Journal of Quantitative Spectroscopy & Radiative Transfer

http://arxiv.org/pdf/1404.6050

Direct detection of exoplanets in the 3 - 10 micron range with E-ELT/METIS

Sascha P. Quanz1, Ian Crossfield2, Michael R. Meyer1, Eva Schmalzl3 and Jenny Held1

1 ETH Zurich, Zurich, Switzerland2 Max Planck Institute for Astronomy, Heidelberg, Germany3 Sterrewacht Leiden, Leiden, The Netherlands

E-mail contact: sascha.quanz at astro.phys.ethz.ch

We quantify the scientific potential for exoplanet imaging with the Mid-infrared E-ELT Imager and Spectrograph(METIS) foreseen as one of the instruments of the European Extremely Large Telescope (E-ELT). We focus on twomain science cases: (1) the direct detection of known gas giant planets found by radial velocity (RV) searches; and(2) the direct detection of small (1 – 4 Rearth) planets around the nearest stars. Under the assumptions made in

29

our modeling, in particular on the achievable inner working angle and sensitivity, our analyses reveal that within areasonable amount of observing time METIS is able to image >20 already known, RV-detected planets in at leastone filter. Many more suitable planets with dynamically determined masses are expected to be found in the comingyears with the continuation of RV-surveys and the results from the GAIA astrometry mission. In addition, byextrapolating the statistics for close-in planets found by Kepler, we expect METIS might detect ∼10 small planetswith equilibrium temperatures between 200 - 500 K around the nearest stars. This means that (1) METIS will helpconstrain atmospheric models for gas giant planets by determining for a sizable sample their luminosity, temperatureand orbital inclination; and (2) METIS might be the first instrument to image a nearby (super-)Earth-sized planetwith an equilibrium temperature near that expected to enable liquid water on a planet surface.

Accepted by the International Journal of Astrobiology (Cambridge University Press); Invited contribution to anupcoming special issue.

http://arxiv.org/pdf/1404.0831

Tracing the ISM magnetic field morphology: The potential of multi-wavelength polar-ization measurements

Stefan Reissl1, Sebastian Wolf1 and Daniel Seifried2

1 Institut fr Theoretische Physik und Astrophysik, Christian-Albrechts-Universitt zu Kiel, Leibnizstrae 15, 24098 Kiel,Germany2 Hamburger Sternwarte, Universitt Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany

E-mail contact: sreissl at astrophysik.uni-kiel.de

Aims. We present a case study to demonstrate the potential of multi-wavelength polarization measurements. Theaim is to investigate the effects that dichroic polarization and thermal re-emission have on tracing the magnetic fieldin the interstellar medium (ISM). Furthermore, we analyze the crucial influence of imperfectly aligned compact dustgrains on the resulting synthetic continuum polarization maps.Methods. We developed an extended version of the well-known 3D Monte-Carlo radiation transport code MC3D formulti-wavelength polarization simulations running on an adaptive grid.We investigated the interplay between radia-tion, magnetic fields and dust grains. Our results were produced by post-processing both ideal density distributionsand sophisticated magnetohydrodynamic (MHD) collapse simulations with radiative transfer simulations. We derivedspatially resolved maps of intensity, optical depth, and linear and circular polarization at various inclination anglesand scales in a wavelength range from 7µm to 1mm.Results. We predict unique patterns in linear and circular polarization maps for different types of density distribu-tions and magnetic field morphologies for test setups and sophisticated MHD collapse simulations. We show thatalignment processes of interstellar dust grains can significantly influence the resulting synthetic polarization maps.Multi-wavelength polarization measurements allow one to predict the morphology of the magnetic field inside theISM. The interpretation of polarization measurements of complex structures still remains ambiguous because of thelarge variety of the predominant parameters in the ISM.

Accepted by A&A 2014

http://arxiv.org/pdf/1404.5286

Gas and dust in the Beta Pictoris Moving Group as seen by the Herschel Space Obser-vatory

P. Riviere-Marichalar1,2, D. Barrado1, B.Montesinos1, G. Duchene3,4, H. Bouy1, C. Pinte4, F. Menard4,5,

J. Donaldson6, C. Eiroa7, A.V. Krivov8, I. Kamp2, I. Mendigutıa9, W.R.F. Dent10, and J. Lillo-Box1

1 Centro de Astrobiologıa (INTACSIC) Depto. Astrofısica, POB 78, ESAC Campus, 28691 Villanueva de la Canada,Spain2 Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands3 Astronomy Department, University of California, Berkeley CA 94720-3411 USA4 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique (IPAG) UMR 5274, Grenoble, F-38041,France

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5 Laboratorio Franco-Chileno de Astronomia (UMI 3386: CNRS U de Chile / PUC / U Conception), Santiago, Chile6 Department of Astronomy, University of Maryland, College Park, MD 230742, USA7 Dep. de Fısica Teorica, Fac. de Ciencias, UAM Campus Cantoblanco, 28049 Madrid, Spain8 Astrophysikalisches Institut und Universitatssternwarte, Friedrich-Schiller-Universitat Jena, Schillergachen 23, 07745Jena, Germany9 Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978, USA10 ALMA, Avda Apoquindo 3846, Piso 19, Edicio Alsacia, Las Condes, Santiago, Chile

E-mail contact: riviere at astro.rug.nl

Context. Debris discs are thought to be formed through the collisional grinding of planetesimals, and can be consideredas the outcome of planet formation. Understanding the properties of gas and dust in debris discs can help us tocomprehend the architecture of extrasolar planetary systems. Herschel Space Observatory far-infrared (IR) photometryand spectroscopy have provided a valuable dataset for the study of debris discs gas and dust composition. This paperis part of a series of papers devoted to the study of Herschel PACS observations of young stellar associations.Aims. This work aims at studying the properties of discs in the Beta Pictoris Moving Group (BPMG) through far-IRPACS observations of dust and gas.Methods. We obtained Herschel-PACS far-IR photometric observations at 70, 100 and 160 µm of 19 BPMG members,together with spectroscopic observations of four of them. Spectroscopic observations were centred at 63.18 µm and157 µm, aiming to detect [OI] and [CII] emission. We incorporated the new far-IR observations in the SED of BPMGmembers and fitted modified blackbody models to better characterise the dust content.Results. We have detected far-IR excess emission toward nine BPMG members, including the first detection of an IRexcess toward HD 29391.The star HD 172555, shows [OI] emission, while HD 181296, shows [CII] emission, expandingthe short list of debris discs with a gas detection. No debris disc in BPMG is detected in both [OI] and [CII]. Thediscs show dust temperatures in the range 55 to 264 K, with low dust masses (6.6 × 10−5 M⊕ to 0.2 M⊕) and radiifrom blackbody models in the range 3 to 82 AU. All the objects with a gas detection are early spectral type stars witha hot dust component.

Accepted by A&A

http://arxiv.org/pdf/1404.1815

A Dusty M5 Binary in the beta Pictoris Moving Group

David R. Rodriguez1, B. Zuckerman2, Jacqueline K. Faherty3,4, and Laura Vican2

1 Departamento de Astronomıa, Universidad de Chile, Casilla 36-D, Santiago, Chile2 Dept. of Physics & Astronomy, University of California, Los Angeles 90095, USA3 Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington,DC 20015, USA4 Hubble Fellow

E-mail contact: drodrigu at das.uchile.cl

We report the identification of a new wide separation binary (LDS 5606) in the ∼20 Myr-old beta Pic moving group.This M5+M5 pair has a projected separation of 26′′, or ∼1700 AU at a distance of 65 pc. Both stars host warmcircumstellar disks and many strong hydrogen and helium emission lines. Spectroscopic observations reveal signaturesof youth for both stars and on-going mass accretion in the primary. The properties of LDS 5606 make it an olderanalog to the ∼8 Myr TWA 30 system, which is also composed of a pair of widely separated mid-M dwarfs, eachhosting their own warm circumstellar disks. LDS 5606 joins a rather exclusive club of only 3 other known stellarsystems where both members of a binary, far from any molecular cloud, are orbited by detected circumstellar disks.

Accepted by A&A

http://arxiv.org/pdf/1404.2543

Protoplanetary disc evolution affected by star-disc interactions in young stellar clusters

Giovanni P. Rosotti1,2,3, James E. Dale2,3, Maria de Juan Ovelar4, David A. Hubber2,3, J.M. Diederik

Kruijssen5, Barbara Ercolano2,3, and Stefanie Walch5

1 Max-Planck-Institut fur extraterrestrische Physik, Giessenbachstraße, D-85748 Garching, Germany

31

2 Excellence Cluster Universe, Boltzmannstr. 2, D-85748 Garching, Germany3 Universitats-Sternwarte Munchen, Scheinerstraße 1, D-81679 Munchen, Germany4 Leiden Observatory, Leiden University, P.O. Box 9513, 2300RA Leiden, The Netherlands5 Max-Planck-Institut fur Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching, Germany

E-mail contact: rosotti at usm.lmu.de

Most stars form in a clustered environment. Therefore, it is important to assess how this environment influencesthe evolution of protoplanetary discs around young stars. In turn, this affects their ability to produce planets andultimately life. We present here for the first time 3D SPH/N-body simulations that include both the hydrodynamicalevolution of the discs around their natal stars, as well as the dynamics of the stars themselves. The discs are viscouslyevolving, accreting mass onto the central star and spreading. We find penetrating encounters to be very destructivefor the discs as in previous studies, although the frequency of such encounters is low. We also find, however, thatencounter influence the disc radii more strongly than other disc properties such as the disc mass. The disc sizes areset by the competition between viscous spreading and the disruptive effect of encounters. As discs spread, encountersbecome more and more important. In the regime of rapid spreading encounters simply truncate the discs, strippingthe outer portions. In the opposite regime, we find that the effect of many distant encounters is able to limit the discsize. Finally, we predict from our simulations that disc sizes are limited by encounters at stellar densities exceeding ∼2–3 × 103 pc−2.

Accepted by MNRAS

http://arxiv.org/pdf/1404.1931

Class 0 Protostars in the Perseus Molecular Cloud: A Correlation Between the YoungestProtostars and the Dense Gas Distribution

S.I. Sadavoy1,2,3, J. Di Francesco1,2, Ph. Andre4, S. Pezzuto5, J.-P. Bernard6,7, A. Maury4, A. Men’shchikov4,

F. Motte4, Q. Nguyen-Luong8, N. Schneider9, D. Arzoumanian10, M. Benedettini5, S. Bontemps9,11, D.

Elia5, M. Hennemann4, T. Hill12, V. Konyves4,10, F. Louvet4, N. Peretto13, A. Roy4 and G. J. White14,15

1 Department of Physics & Astronomy, University of Victoria, PO Box 355, STN CSC, Victoria, BC, V8W 3P6,Canada2 National Research Council Canada, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada3 Current address: Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117 Heidelberg, Germany4 Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/Service d’Astrophysique, Saclay, 91191 Gif-sur-Yvette, France5 Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133, Rome, Italy6 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France7 Universite de Toulouse, UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France8 Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON, M5S 3H8, Canada9 Universite de Bordeaux, LAB, UMR 5804, F-33270, Floirac, France10 IAS, CNRS (UMR 8617), Universite Paris-Sud 11, Batiment 121, 91400 Orsay, France11 CNRS, LAB, UMR 5804, F-33270, Floirac, France12 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura 763-0355, Santiago, Chile13 School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, UK14 Department of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, UK15 The Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK

E-mail contact: sadavoy at mpia.de

We use PACS and SPIRE continuum data at 160 um, 250 um, 350 um, and 500 um from the Herschel Gould Belt Surveyto sample seven clumps in Perseus: B1, B1-E, B5, IC348, L1448, L1455, and NGC1333. Additionally, we identifyand characterize the embedded Class 0 protostars using detections of compact Herschel sources at 70 um as well asarchival Spitzer catalogues and SCUBA 850 um photometric data. We identify 28 candidate Class 0 protostars, fourof which are newly discovered sources not identified with Spitzer. We find that the star formation efficiency of clumps,as traced by Class 0 protostars, correlates strongly with the flatness of their respective column density distributionsat high values. This correlation suggests that the fraction of high column density material in a clump reflects only itsyoungest protostellar population rather than its entire source population. We propose that feedback from either the

32

formation or evolution of protostars changes the local density structure of clumps.

Accepted by ApJL

http://arxiv.org/pdf/1404.7142

Orbital Motion in Pre-Main Sequence Binaries

G. H. Schaefer1, L. Prato2, M. Simon3 and J. Patience4

1 The CHARA Array of Georgia State University, Mount Wilson Observatory, Mount Wilson, CA 91023, USA2 Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA3 Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA4 Astrophysics Group, School of Physics, University of Exeter, Exeter, EX4 4QL, UK; School of Earth and SpaceExploration, Arizona State University, PO Box 871404, Tempe, Arizona, 85287, USA

E-mail contact: schaefer at chara-array.org

We present results from our ongoing program to map the visual orbits of pre-main sequence binaries in the Taurus starforming region using adaptive optics imaging at the Keck Observatory. We combine our results with measurementsreported in the literature to analyze the orbital motion for each binary. We present preliminary orbits for DF Tau, TTau S, ZZ Tau, and the Pleiades binary HBC 351. Seven additional binaries show curvature in their relative motion.Currently, we can place lower limits on the orbital periods for these systems; full solutions will be possible with moreorbital coverage. Five other binaries show motion that is indistinguishable from linear motion. We suspect that thesesystems are bound and might show curvature with additional measurements in the future. The observations reportedherein lay critical groundwork toward the goal of measuring precise masses for low-mass pre-main sequence stars.

Accepted by Astronomical Journal

http://arxiv.org/pdf/1405.0225

First spectroscopic observations of the sub-stellar companion of the young debris diskstar PZ Telescopii

T.O.B. Schmidt1, M. Mugrauer1, R. Neuhauser1, N. Vogt2, S. Witte3, P.H. Hauschildt3, Ch. Helling4,

and A. Seifahrt5

1 Astrophysikalisches Institut und Universitats-Sternwarte, Universitat Jena, Schillergaßchen 2-3, 07745 Jena, Ger-many2 Departamento de Fısica y Astronomıa, Universidad de Valparaıso, Avenida Gran Bretana 1111, Valparaıso, Chile3 Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany4 SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, UK5 Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., IL 60637, USA

E-mail contact: tobi at astro.uni-jena.de

In 2010 a sub-stellar companion to the solar analog pre-main sequence star PZ Tel and member of the about 12 Myr oldβ Pic moving group was found by high-contrast direct imaging independently by two teams. In order to determine thebasic parameters of this companion more precisely and independent of evolutionary models, hence age independent,we obtained follow-up spectroscopic observations of primary and companion. We use the Spectrograph for INtegralField Observations in the Near Infrared (SINFONI) at the Very Large Telescope Unit 4/YEPUN of ESO’s ParanalObservatory in H+K band and process the data using the spectral deconvolution technique. The resulting spectrum ofthe companion is then compared to a grid of Drift-Phoenix synthetic model spectra, a combination of a general-purposemodel atmosphere code with a non-equilibrium, stationary cloud and dust model, using a χ2 minimization analysis.We find a best fitting spectral type of G6.5 for PZ Tel A. The extracted spectrum of the sub-stellar companion, at aspatial position compatible with earlier orbit estimates, yields a temperature Teff = 2500+138

−115 K, a visual extinction

AV = 0.53+0.84−0.53 mag, a surface gravity of log g = 3.50+0.51

−0.30 dex, and a metallicity at the edge of the grid of [M/H] =

0.30−0.30 dex. We derive a luminosity of log(Lbol/L⊙) = −2.66+0.06−0.08, a radius of R = 2.42+0.28

−0.34 RJup and a mass of

M = 7.5+16.9−4.3 MJup for the PZ Tel companion, being consistent with most earlier estimates using photometry alone.

Combining our results with evolutionary models, we find a best fitting mass of about 21 Jupiter masses at an age

33

corresponding to the recently determined lithium depletion age of 7+4−2 Myr. Hence, the PZ Tel companion is most

likely a wide brown dwarf companion in the 12+8−4 Myr old β Pic moving group.

Accepted by A&A

http://arxiv.org/pdf/1404.2870

Dancing with the Stars: Formation of the Fomalhaut triple system and its effect on thedebris disks

Andrew Shannon1, Cathie Clarke1, and Mark Wyatt1

1 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, United Kingdom of Great Britainand Northern Ireland, CB3 0HA

E-mail contact: shannon at ast.cam.ac.uk

Fomalhaut is a triple system, with all components widely separated (∼105 AU). Such widely separated binaries arethought to form during cluster dissolution, but that process is unlikely to form such a triple system. We explore analternative scenario, where A and C form as a tighter binary from a single molecular cloud core (with semimajoraxis ∼104 AU), and B is captured during cluster dispersal. We use N-body simulations augmented with the Galactictidal forces to show that such a system naturally evolves into a Fomalhaut-like system in about half of cases, on atimescale compatible with the age of Fomalhaut. From initial non-interacting orbits, Galactic tides drive cycles inB’s eccentricity that lead to a close encounter with C. After several close encounters, typically lasting tens of millionsof years, one of the stars is ejected. The Fomalhaut-like case with both components at large separations is almostinvariably a precursor to the ejection of one component, most commonly Fomalhaut C. By including circumstellardebris in a subset of the simulations, we also show that such an evolution usually does not disrupt the coherentlyeccentric debris disk around Fomalhaut A, and in some cases can even produce such a disk. We also find that the finaleccentricity of the disk around A and the disk around C are correlated, which may indicate that the dynamics of thethree stars stirred C’s disk, explaining its unusual brightness.

Accepted by MNRAS

http://arxiv.org/pdf/1404.7136

Chandra Resolves the T Tauri Binary System RW Aur

Stephen L. Skinner1 and Manuel Gudel2

1 CASA, Univ. of Colorado, Boulder, CO, USA 80309-03892 Dept. of Astrophysics, Univ. of Vienna, Turkenschanzstr. 17, A-1180 Vienna, Austria

E-mail contact: stephen.skinner at colorado.edu

RW Aur is a multiple T Tauri system consisting of an early-K type primary (A) and a K5 companion (B) at aseparation of 1.′′4. RW Aur A drives a bipolar optical jet that is well-characterized optically. We present results ofa sensitive Chandra observation whose primary objective was to search for evidence of soft extended X-ray emissionalong the jet, as has been seen for a few other nearby T Tauri stars. The binary is clearly resolved by Chandra andboth stars are detected as X-ray sources. The X-ray spectra of both stars reveal evidence for cool and hot plasma.Suprisingly, the X-ray luminosity of the less-massive secondary is at least twice that of the primary and is variable.The disparity is attributed to the primary whose X-ray luminosity is at the low end of the range for classical T Tauristars of similar mass based on established correlations. Deconvolved soft-band images show evidence for slight outwardelongation of the source structure of RW Aur A along the blueshifted jet axis inside the central arcsecond. In addition,a faint X-ray emission peak is present on the redshifted axis at an offset of 1.′′2±0.′′2 arcsec from the star. Deprojectedjet speeds determined from previous optical studies are too low to explain this faint emission peak as shock-heated jetplasma. Thus, unless flow speeds in the redshifted jet have been underestimated, other mechanisms such as magneticjet heating may be involved.

Accepted by ApJ

http://arxiv.org/pdf/1404.2631

34

A Test of Star Formation Laws in Disk Galaxies. II. Dependence on dynamical proper-ties

Chutipong Suwannajak1, Jonathan C. Tan1 and Adam K. Leroy2

1 University of Florida, USA2 NRAO, Charlottesville, USA

E-mail contact: jt at astro.ufl.edu

We use the observed radial profiles of the mass surface densities of total, Σg, and molecular, ΣH2, gas, rotation velocityand star formation rate (SFR) surface density, Σsfr, of the molecular-rich (ΣH2 ≥ ΣHI/2) regions of 16 nearby diskgalaxies to test several star formation laws: a ”Kennicutt-Schmidt” law, Σsfr = AgΣ

1.5g,2; a ”Constant Molecular” law,

Σsfr = AH2ΣH2,2; the turbulence-regulated laws of Krumholz & McKee (KM05) and Krumholz, McKee & Tumlinson(KMT09), a ”Gas-Ω” law, Σsfr = BΩΣgΩ; and a shear-driven ”GMC Collision” law, Σsfr = BCCΣgΩ(1− 0.7β), whereβ ≡ d ln vcirc/d ln r. If allowed one free normalization parameter for each galaxy, these laws predict the SFR with rmserrors of factors of 1.4 to 1.8. If a single normalization parameter is used by each law for the entire galaxy sample,then rms errors range from factors of 1.5 to 2.1. Although the Constant Molecular law gives the smallest rms errors,the improvement over the KMT, Kennicutt-Schmidt and GMC Collision laws is not especially significant, particularlygiven the different observational inputs that the laws utilize and the scope of included physics, which ranges fromempirical relations to detailed treatment of interstellar medium processes. We next search for systematic variationof star formation law parameters with local and global galactic dynamical properties of disk shear rate (related toβ), rotation speed and presence of a bar. We demonstrate with high significance that higher shear rates enhancestar formation efficiency per local orbital time. Such a trend is expected if GMC collisions play an important rolein star formation, while an opposite trend would be expected if development of disk gravitational instabilities is thecontrolling physics.

Accepted by Astrophysical Journal

http://arxiv.org/pdf/1404.1359

A very young, compact bipolar H2O maser outflow in the intermediate-mass star-forming LkHα 234 region

J.M. Torrelles1, S. Curiel2, R. Estalella3, G. Anglada4, J.F. Gomez4, J. Canto2, N.A. Patel5, M.A.

Trinidad6, J.M. Girart7, C. Carrasco-Gonzalez8, L.F. Rodrıguez8

1 Institut de Ciencies de l’Espai (CSIC-IEEC) and Institut de Ciencies del Cosmos (UB-IEEC), Martı i Franques 1,08028 Barcelona, Spain2 Instituto de Astronomıa (UNAM), Apartado 70-264, 04510 Mexico D. F., Mexico3 Departament d’Astronomia i Meteorologia and Institut de Ciencies del Cosmos (IEEC-UB), Universitat de Barcelona,Martı i Franques 1, 08028 Barcelona, Spain4 Instituto de Astrofısica de Andalucıa (CSIC), Apartado 3004, 18080 Granada, Spain5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA6 Departamento de Astronomıa, Universidad de Guanajuato, Apdo. Postal 144, 36000 Guanajuato, Mexico7 Institut de Ciencies de l’Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, C5p 2, 08193 Bellaterra, Spain8 Centro de Radioastronomıa y Astrofısica (UNAM), 58089 Morelia, Mexico

E-mail contact: torrelles at ieec.cat

We report multi-epoch VLBI H2O maser observations towards the compact cluster of YSOs close to the Herbig Be starLkHα 234. This cluster includes LkHα 234 and at least nine more YSOs that are formed within projected distances of∼10′′ (∼9,000 AU). We detect H2O maser emission towards four of these YSOs. In particular, our VLBI observations(including proper motion measurements) reveal a remarkable very compact (∼0.2′′ ≃ 180 AU), bipolar H2O maseroutflow emerging from the embedded YSO VLA 2. We estimate a kinematic age of ∼40 yr for this bipolar outflow,with expanding velocities of ∼20 km s−1 and momentum rate MwVw ≃ 10−4–10−3 M⊙ yr−1 km s−1 × (Ω/4π),powered by a YSO of a few solar masses. We propose that the outflow is produced by recurrent episodic jet ejectionsassociated with the formation of this YSO. Short-lived episodic ejection events have previously been found towardshigh-mass YSOs. We show now that this behaviour is also present in intermediate-mass YSOs. These short-livedepisodic ejections are probably related to episodic increases in the accretion rate, as observed in low-mass YSOs. We

35

predict the presence of an accretion disk associated with VLA 2. If detected, this would represent one of the fewknown examples of intermediate-mass stars with a disk-YSO-jet system at scales of a few hundred AU.

Accepted by MNRAS

http://arxiv.org/pdf/1404.7273

Near-infrared emission from sublimating dust in collisionally active debris disks

R. van Lieshout1, C. Dominik1,2, M. Kama3,1 and M. Min1

1 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, TheNetherlands2 Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Nether-lands3 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands

E-mail contact: r.vanlieshout at uva.nl

Hot exozodiacal dust is thought to be responsible for excess near-infrared (NIR) emission emanating from the innermostparts of some debris disks. The origin of this dust, however, is still a matter of debate.We test whether hot exozodiacal dust can be supplied from an exterior parent belt by Poynting–Robertson (P–R)drag, paying special attention to the pile-up of dust that occurs due to the interplay of P–R drag and dust sublimation.Specifically, we investigate whether pile-ups still occur when collisions are taken into account, and if they can explainthe observed NIR excess.We computed the steady-state distribution of dust in the inner disk by solving the continuity equation. First, wederived an analytical solution under a number of simplifying assumptions. Second, we developed a numerical debrisdisk model that for the first time treats the complex interaction of collisions, P–R drag, and sublimation in a self-consistent way. From the resulting dust distributions, we generated thermal emission spectra and compare these toobserved excess NIR fluxes.We confirm that P–R drag always supplies a small amount of dust to the sublimation zone, but find that a fullyconsistent treatment yields a maximum amount of dust that is about 7 times lower than that given by analyticalestimates. The NIR excess due to this material is much less (<10−3 for A-type stars with parent belts at >1 AU)than the values derived from interferometric observations (∼10−2). Pile-up of dust still occurs when collisions areconsidered, but its effect on the NIR flux is insignificant. Finally, the cross-section in the innermost regions is clearlydominated by barely bound grains.

Accepted by A&A

http://arxiv.org/pdf/1404.3271

Stellar magnetism: empirical trends with age and rotation

A. A. Vidotto1,2, S. G. Gregory1, M. Jardine1, J.-F. Donati3, P. Petit3, J. Morin4, C. P. Folsom3, J.

Bouvier5, A. C. Cameron1, G. Hussain6, S. Marsden7, I. A Waite7, R. Fares1, S. Jeffers8 and J. D. do

Nascimento Jr9

1 SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK2 Observatoire de Geneve, Universite de Geneve, Chemin des Mailletes 51, Versoix, 1290, Switzerland3 LATT - CNRS/Universite de Toulouse, 14 Av. E. Belin, Toulouse, F-31400, France4 LUPM-UMR5299, CNRS & Universite Montpellier II, Place E. Bataillon, Montpellier, F-34095, France5 UJF-Grenoble 1/CNRS-INSU, Inst. de Planetologie et d’Astrophysique de Grenoble, Grenoble, F-38041, France6 ESO, Karl-Schwarzschild-Strasse 2, D-85748, Garching bei Mnchen, Germany7 Computational Engineering and Science Research Centre, University of Southern Queensland, Toowoomba, 4350,Australia8 Institut fur Astrophysik, Georg-August-Universitat, Friedrich-Hund-Platz 1, D-37077, Goettingen, Germany9 Dep. de Fisica Teorica e Exp., Un. Federal do Rio Grande do Norte, CEP: 59072-970 Natal, RN, Brazil

E-mail contact: aline.vidotto at unige.ch

We investigate how the observed large-scale surface magnetic fields of low-mass stars (∼0.1-2M⊙), reconstructed

36

through Zeeman-Doppler imaging (ZDI), vary with age t, rotation period Prot, Rossby number Ro and X-ray emission.Our sample consists of 104 magnetic maps of 73 stars, from accreting pre-main sequence to main-sequence objects,spanning ages from ∼ 1 Myr to ∼ 10 Gyr. For non-accreting dwarfs we empirically find that the unsigned averagelarge-scale surface magnetic field 〈|BV |〉 is related to age as t−0.655±0.045. This relation has a similar power dependencyto that identified in the seminal work of Skumanich (1972), which has served as the basis of gyrochronology, wherebystellar ages can be derived from rotation measurements. Our relation could therefore be used as an alternative methodto estimate the age of stars (“magnetochronology”). We also find that 〈|BV |〉 ∝ P−1.32±0.14

rot and 〈|BV |〉 ∝ Ro−1.38±0.14,supporting the presence of a linear-type dynamo of the large-scale field. The trends we find for large-scale stellarmagnetism from ZDI studies are consistent with the trends found from Zeeman broadening measurements, whichare sensitive to the unsigned large- and small-scale magnetic field 〈|BI |〉. These similarities indicate that the fieldsrecovered from both techniques are coupled to each other, suggesting that small- and large-scale fields could share thesame dynamo field generation processes. We also investigate how the small- and large-scale structures contribute toX-ray emission. These contributions have similar slopes within 3σ, but samples with large dynamic range of 〈|BI |〉 arerequired to better constrain this result. For the accreting objects, fewer statistically significant relations are found,with one being a correlation between the unsigned magnetic flux ΦV and Prot, which we attribute to a signature ofstar-disc interaction, rather than being driven by the dynamo magnetic field generation process.

Accepted by MNRAS

http://arxiv.org/pdf/1404.2733

Complex organic molecules in protoplanetary disks

Catherine Walsh1, T. J. Millar2, Hideko Nomura3,4,5, Eric Herbst6,7, Susanna Widicus Weaver8, Yuri

Aikawa9, Jacob C. Laas8 and Anton I. Vasyunin10,11

1 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands2 Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, University Road,Belfast, BT7 1NN, UK3 Department of Astronomy, Graduate School of Science, Kyoto University, 606-8502, Kyoto, Japan4 National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo, 181-8588, Japan5 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, 152-8551, Tokyo, Japan6 Departments of Physics, Chemistry and Astronomy, The Ohio State University, Columbus, OH, 43210, USA7 Departments of Chemistry, Astronomy, and Physics, University of Virginia, Charlottesville, VA, 22904, USA8 Department of Chemistry, Emory University, Atlanta, GA, 30322, USA9 Department of Earth and Planetary Sciences, Kobe University, 1-1 Rokkodai-cho, Nada, 657-8501, Kobe, Japan10 Department of Chemistry, Emory University, Atlanta, GA, 30322, USA11 Visiting Scientist, Ural Federal University, 620075, Ekaterinburg, Russia

E-mail contact: cwalsh at strw.leidenuniv.nl

Context: Protoplanetary disks are vital objects in star and planet formation, possessing all the material, gas and dust,which may form a planetary system orbiting the new star. Small, simple molecules have traditionally been detectedin protoplanetary disks; however, in the ALMA era, we expect the molecular inventory of protoplanetary disks tosignificantly increase.Aims: We investigate the synthesis of complex organic molecules (COMs) in protoplanetary disks to put constraintson the achievable chemical complexity and to predict species and transitions which may be observable with ALMA.Methods: We have coupled a 2D steady-state physical model of a protoplanetary disk around a typical T Tauri starwith a large gas-grain chemical network including COMs. We compare the resulting column densities with thosederived from observations and perform ray-tracing calculations to predict line spectra. We compare the synthesisedline intensities with current observations and determine those COMs which may be observable in nearby objects. Wealso compare the predicted grain-surface abundances with those derived from cometary comae observations.Results: We find COMs are efficiently formed in the disk midplane via grain-surface chemical reactions, reachingpeak grain-surface fractional abundances ∼ 10−6-10−4 that of the H nuclei number density. COMs formed on grainsurfaces are returned to the gas phase via non-thermal desorption; however, gas-phase species reach lower fractionalabundances than their grain-surface equivalents, ∼ 10−12-10−7. Including the irradiation of grain mantle material

37

helps build further complexity in the ice through the replenishment of grain-surface radicals which take part in furthergrain-surface reactions. There is reasonable agreement with several line transitions of H2CO observed towards TTauri star-disk systems. There is poor agreement with HC3N lines observed towards LkCa 15 and GO Tau and wediscuss possible explanations for these discrepancies. The synthesised line intensities for CH3OH are consistent withupper limits determined towards all sources. Our models suggest CH3OH should be readily observable in nearbyprotoplanetary disks with ALMA; however, detection of more complex species may prove challenging, even withALMA ”Full Science” capabilities. Our grain-surface abundances are consistent with those derived from cometarycomae observations providing additional evidence for the hypothesis that comets (and other planetesimals) formed viathe coagulation of icy grains in the Sun’s natal disk.

Accepted by Astronomy and Astrophysics

http://adsabs.harvard.edu/pdf/2014A%26A...563A..33W

ESO-Ha 574 and Par-Lup3-4 jets: Exploring the spectral, kinematical and physicalproperties

E.T. Whelan1, R. Bonito2,3, S. Antoniucci4, J.M. Alcala5, T. Giannini4, B. Nisini4, F. Bacciotti6, L.

Podio6,7, B. Stelzer3 and F. Comeron8

1 Institut fur Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Eberhard Karls Universitat,72076 Tubingen, Germany2 Universita di Palermo, P.zza del Parlamento 1, 90134 Palermo, Italy3 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy4 INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio, Italy5 INAF - Osservatorio Astronomico di Capodimonte, via Moiariello, 16, 80131 Napoli, Italy6 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy7 UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041Grenoble, France8 ESO, Alonso de Crdova 3107, Castilla 19001, Santiago 19, Chile

E-mail contact: emma.whelan at astro.uni-tuebingen.de

In this paper a comprehensive analysis of VLT/X-Shooter observations of two jet systems, namely ESO-Hα 574 a K8classical T Tauri star and Par-Lup 3-4 a very low mass (0.13 M⊙) M5 star, is presented. Both stars are known to havenear-edge on accretion disks. A summary of these first X-shooter observations of jets was given in a 2011 letter. Thenew results outlined here include flux tables of identified emission lines, information on the morphology, kinematicsand physical conditions of both jets and, updated estimates of Mout / Macc. Asymmetries in the ESO-Hα 574 flow areinvestigated while the Par-Lup 3-4 jet is much more symmetric. The density, temperature, and therefore origin of thegas traced by the Balmer lines are investigated from the Balmer decrements and results suggest an origin in a jet forESO-Hα 574 while for Par-Lup 3-4 the temperature and density are consistent with an accretion flow. Macc is estimatedfrom the luminosity of various accretion tracers. For both targets, new luminosity relationships and a re-evaluation ofthe effect of reddening and grey extinction (due to the edge-on disks) allows for substantial improvements on previousestimates of Macc. It is found that log(Macc) = -9.15 ± 0.45 M⊙yr

−1 and -9.30 ± 0.27 M⊙yr−1 for ESO-Hα 574 and

Par-Lup 3-4, respectively. Additionally, the physical conditions in the jets (electron density, electron temperature, andionisation) are probed using various line ratios and compared with previous determinations from iron lines. The resultsare combined with the luminosity of the [SII]λ6731 line to derive Mout through a calculation of the gas emissivitybased on a 5-level atom model. As this method for deriving Mout comes from an exact calculation based on the jetparameters (measured directly from the spectra) rather than as was done previously from an approximate formulabased on the value of the critical density at an assumed unknown temperature, values of Mout are far more accurate.Overall the accuracy of earlier measurements of Mout / Macc is refined and Mout / Macc = 0.5 (+1.0)(-0.2) and 0.3(+0.6)(-0.1) for the ESO-Hα 574 red and blue jets, respectively, and 0.05 (+0.10)(-0.02) for both the Par-Lup 3-4 redand blue jets. While the value for the total (two-sided) Mout / Macc in ESO-Hα 574 lies outside the range predictedby magneto-centrifugal jet launching models, the errors are large and the effects of veiling and scattering on extinctionmeasurements, and therefore the estimate of Macc, should also be considered. ESO-Hα 574 is an excellent case studyfor understanding the impact of an edge-on accretion disk on the observed stellar emission. The improvements in thederivation of Mout / Macc means that this ratio for Par-Lup 3-4 now lies within the range predicted by leading models,

38

as compared to earlier measurements for very low mass stars. Par-Lup 3-4 is one of a small number of brown dwarfsand very low mass stars which launch jets. Therefore, this result is important in the context of understanding howMout / Macc and, thus, jet launching mechanisms for the lowest mass jet driving sources, compare to the case of thewell-studied low mass stars.

Accepted by Astronomy and Astrophysics

http://arxiv.org/pdf/1403.3232

Multi-epoch Sub-arcsecond [Fe II] Spectroimaging of the DG Tau Outflows with NIFS.I. First data epoch

Marc C White1, Peter J McGregor1, Geoffrey V Bicknell1, Raquel Salmeron1 and Tracy L Beck2

1 Research School of Astronomy & Astrophysics, The Australian National University, Cotter Rd., Weston, ACT, 2611,Australia2 Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD, 21218, USA

E-mail contact: marc.white at anu.edu.au

Investigating the outflows emanating from young stellar objects (YSOs) on sub-arcsecond scales provides importantclues to the nature of the underlying accretion-ejection process occurring near the central protostar. We have investi-gated the structures and kinematics of the outflows driven by the YSO DG Tauri, using the Near-infrared Integral FieldSpectrograph (NIFS) on Gemini North. The blueshifted outflow shows two distinct components in [Fe II] 1.644 µmemission, which are separated using multi-component line fitting. Jet parameters are calculated for the high-velocitycomponent. A stationary recollimation shock is observed, in agreement with previous X-ray and FUV observations.The presence of this shock indicates that the innermost streamlines of the high-velocity component are launched ata very small radius, 0.01–0.15 AU, from the central star. The jet accelerates and expands downstream of the recol-limation shock; the ‘acceleration’ is likely a sign of velocity variations in the jet. No evidence of rotation is found,and we compare this non-detection to previous counter-claims. Moving jet knots, likely the result of the jet velocityvariations, are observed. One of these knots moves more slowly than previously observed knots, and the knot ejectioninterval appears to be non-periodic. An intermediate-velocity component surrounds this central jet, and is interpretedas the result of a turbulent mixing layer along the jet boundaries generated by lateral entrainment of material bythe high-velocity jet. Lateral entrainment requires the presence of a magnetic field of strength a few mG or less athundreds of AU above the disc surface, which is argued to be a reasonable proposition. In H2 1-0 S(1) 2.1218 µmemission, a wide-angle, intermediate-velocity blueshifted outflow is observed. Both outflows are consistent with beinglaunched by a magnetocentrifugal disc wind, although an X-wind origin for the high-velocity jet cannot be ruled out.The redshifted outflow of DG Tau takes on a bubble-shaped morphology, which will be discussed in a future paper.

Accepted by MNRAS

http://arxiv.org/pdf/1404.0728

Multi-epoch Sub-arcsecond [Fe II] Spectroimaging of the DG Tau Outflows with NIFS.II. On the Nature of the Bipolar Outflow Asymmetry

Marc C White1, Geoffrey V Bicknell1, Peter J McGregor1 and Raquel Salmeron1

1 Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT, 2611, Australia

E-mail contact: marc.white at anu.edu.au

The origin of bipolar outflow asymmetry in young stellar objects (YSOs) remains poorly understood. It may bedue to an intrinsically asymmetric outflow launch mechanism, or it may be caused by the effects of the ambientmedium surrounding the YSO. Answering this question is an important step in understanding outflow launching.We have investigated the bipolar outflows driven by the T Tauri star DG Tauri on scales of hundreds of AU, usingthe Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The approaching outflow consists of a well-collimated jet, nested within a lower-velocity disc wind. The receding outflow is composed of a single-componentbubble-like structure. We analyse the kinematics of the receding outflow using kinetic models, and determine that itis a quasi-stationary bubble with an expanding internal velocity field. We propose that this bubble forms because thereceding counterjet from DG Tau is obstructed by a clumpy ambient medium above the circumstellar disc surface,

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based on similarities between this structure and those found in the modelling of active galactic nuclei outflows. Wefind evidence of interaction between the obscured counterjet and clumpy ambient material, which we attribute to thelarge molecular envelope around the DG Tau system. An analytical model of a momentum-driven bubble is shown tobe consistent with our interpretation. We conclude that the bipolar outflow from DG Tau is intrinsically symmetric,and the observed asymmetries are due to environmental effects. This mechanism can potentially be used to explainthe observed bipolar asymmetries in other YSO outflows.

Accepted by MNRAS

http://arxiv.org/pdf/1404.6002

A Parametric Modeling Approach to Measuring the Gas Masses of Circumstellar Disks

Jonathan P. Williams1 and William M. J. Best1

1 Institute for Astronomy, University of Hawaii, Honolulu, USA

E-mail contact: jpw at ifa.hawaii.edu

The disks that surround young stars are mostly composed of molecular gas, which is harder to detect and interpretthan the accompanying dust. Disk mass measurements have therefore relied on large and uncertain extrapolations fromthe dust to the gas. We have developed a grid of models to study the dependencies of isotopologue CO line strengthson disk structure and temperature parameters and find that a combination of 13CO and C18O observations providesa robust measure of the gas mass. We apply this technique to Submillimeter Array observations of nine circumstellardisks and published measurements of six well studied disks. We find evidence for selective photodissociation of C18Oand determine masses to within a factor of about three. The inferred masses for the nine disks in our survey rangefrom 0.7− 6MJup, and all are well below the extrapolation from the interstellar medium gas-to-dust ratio of 100. Thisis consistent with the low masses of planets found around such stars, and may be due to accretion or photoevaporationof a dust-poor upper atmosphere. However, the masses may be underestimated if there are more efficient CO depletionpathways than those known in molecular clouds and cold cores.

Accepted by Astrophysical Journal

http://arxiv.org/pdf/1312.0151

A spider-like outflow in Barnard 5 - IRS 1: The transition from a collimated jet to awide-angle outflow?

Luis A. Zapata1, Hector G. Arce2, Erin Brasseld3, Aina Palau4, Nimesh Patel3, and Jaime E. Pineda5

1 Centro de Radioastronomıa y Astrosıca, UNAM campus Morelia, Mexico2 Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06511, USA3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA4 Institut de Ciencies de l’Espai (CSIC-IEEC), Campus UAB-Facultat de Ciencies, Torre C5-parell 2, E-08193 Bel-laterra, Catalunya, Spain5 Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland

E-mail contact: lzapata at crya.unam.mx

We present line and continuum observations made with the Submillimeter Array (SMA) of the young stellar objectBarnard 5 - IRS1 located in the Perseus molecular cloud. Our 12CO (2–1) line observations resolve the high-velocitybipolar northeast-southwest outflow associated with this source. We find that the outflowing gas shows differentstructures at three different velocity regimes, in both lobes, resulting in a spider-like morphology. In addition to thelow-velocity, cone-like (wide-angle) lobes that have previously been observed, we report the presence of intermediate-velocity parabolic shells emerging very close to the Class I protostar, as well as high velocity molecular bullets thatappear to be associated to the optical/IR jet emanating from this source. These compact high-velocity features reachradial velocities of about 50 km s−1 away from the cloud velocity. We interpret the peculiar spider-like morphologyis a result of the molecular material being entrained by a wind with both a collimated jet-like component and awide-angle component. We suggest the outflow is in a transitional evolutionary phase between a mostly jet-driven flowand an outflow in which the entrainment is dominated by the wide-angle wind component. We also detect 1300 µmcontinuum emission at the position of the protostar, which likely arises from the dusty envelope and disk surrounding

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the protostar. Finally, we report the detection of 13CO (2–1) and SO (65–54) emission arising from the outflow andthe location of the young stellar object.

Accepted by MNRAS

http://arxiv.org/pdf/1404.6147

Radiation Transfer of Models of Massive Star Formation. III. The Evolutionary Se-quence

Yichen Zhang1, Jonathan Tan2 and Takashi Hosokawa3

1 Department of Astronomy, Yale University, New Haven, CT 06520, USA2 Departments of Astronomy & Physics, University of Florida, Gainesville, FL 32611, USA3 Department of Physics, University of Tokyo, Tokyo 113-0033, Japan

E-mail contact: yczhang.astro at gmail.com

We present radiation transfer simulations of evolutionary sequences of massive protostars forming from massive densecores in environments of high mass surface densities, based on the Turbulent Core model (McKee & Tan 2003). Theprotostellar evolution is calculated with a multi-zone numerical model, with accretion rate regulated by feedback froman evolving disk-wind outflow cavity. Disk evolution is calculated assuming a fixed ratio of disk to protostellar mass,while core envelope evolution assumes inside-out collapse of the core of fixed outer radius. In this framework, anevolutionary track is determined by three environmental initial conditions: core mass Mc, mass surface density of theambient clump Σcl, and ratio of the core’s initial rotational to gravitational energy βc. Evolutionary sequences withvarious Mc, Σcl, βc are constructed. We find that in a fiducial model with Mc = 60 M⊙, Σcl = 1 g cm−2 and βc = 0.02,the final mass of the protostar reaches at least ∼ 26 M⊙, making the final star formation efficiency >

∼0.43. For eachof the evolutionary tracks, radiation transfer simulations are performed at selected stages, with temperature profiles,spectral energy distributions (SEDs), and multi-wavelength images produced. At a given stage, envelope temperatureis depends strongly on Σcl, with higher temperatures in a higher Σcl core, but only weakly on Mc. The SED andMIR images depend sensitively on the evolving outflow cavity, which gradually widens as the protostar grows. Thefluxes at <

∼100 µm increase dramatically, and the far-IR peaks move to shorter wavelengths. The influence of Σcl

and βc (which determines disk size) are discussed. We find that, despite scatter caused by different Mc, Σcl, βc, andinclinations, sources at a given evolutionary stage appear in similar regions of color-color diagrams, especially whenusing colors with fluxes at >

∼70 µm, where scatter due to inclination is minimized, implying that such diagrams canbe useful diagnostic tools of evolutionary stages of massive protostars. We discuss how intensity profiles along orperpendicular to the outflow axis are affected by environmental conditions and source evolution, and can thus act asadditional diagnostics of the massive star formation process.

Accepted by ApJ

http://arxiv.org/pdf/1312.3370.pdf

Accretion and OH Photodissociation at a Nearby T Tauri System in the beta PictorisMoving Group

B. Zuckerman1, Laura Vican1, and David R. Rodriguez2

1 Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA2 Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile

E-mail contact: ben at astro.ucla.edu

We present spectra of an M-type, binary star system (LDS 5606) that belongs to the nearby ∼20 Myr old β Pictorismoving group. Both stars are very dusty; the dustier member displays optical emission lines from eight elementsindicative of ongoing mass accretion. The spectra of both stars contain oxygen forbidden line emission at 6302 and5579 A, consistent with a recent model of far ultraviolet photodissociation of OH molecules in a circumstellar disk.These are the oldest dwarf stars presently known to display such a phenomena. The spectral energy distribution of thedustier star indicates substantial quantities of dust as hot as 900 K, and its fractional infrared luminosity (LIR)/Lbol)is almost as large as that of the main sequence record holder, V488 Per. The LDS 5606 binary joins a remarkablegroup of very dusty, old, T Tauri stars that belong to widely separated multiple systems.

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Accepted by ApJ

http://arxiv.org/pdf/1404.7481

Abstracts of recently accepted major reviews

Turbulence in the Interstellar Medium

D. Falceta-Goncalves1,2, G. Kowal2, E. Falgarone3, and A.C.-L. Chian4,5,6

1 SUPA, School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK2 Escola de Artes, Ciencias e Humanidades, Universidade de Sao Paulo, Rua Arlindo Bettio 1000, CEP 03828-000,Sao Paulo, Brazil3 LERMA/LRA, CNRS, Ecole Normale Superieure and Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex,France4 Observatoire de Paris, LESIA, CNRS, 92190 Meudon, France5 National Institute for Space Research (INPE) and World Institute for Space Environment Research (WISER), P. O.Box 515, 12227-010 Sao Jose dos Campos-SP, Brazil6 School of Mathematical Sciences, University of Adelaide, Adelaide, SA 5005, Australia

E-mail contact: dfalceta at usp.br

Turbulence is ubiquitous in the interstellar medium and plays a major role in several processes such as the formationof dense structures and stars, the stability of molecular clouds, the amplification of magnetic fields, and the re-acceleration and diffusion of cosmic rays. Despite its importance, interstellar turbulence, alike turbulence in general,is far from being fully understood. In this review we present the basics of turbulence physics, focusing on the statisticsof its structure and energy cascade. We explore the physics of compressible and incompressible turbulent flows, aswell as magnetized cases. The most relevant observational techniques that provide quantitative insights of interstellarturbulence are also presented. We also discuss the main difficulties in developing a three-dimensional view of interstellarturbulence from these observations. Finally, we briefly present what could be the the main sources of turbulence inthe interstellar medium.

Accepted by Nonlinear Processes in Geophysics

http://arxiv.org/pdf/1404.3691

The Link between Magnetic Fields and Cloud/Star Formation

Hua-bai Li1,2, Alyssa Goodman3, T. K. Sridharan3, Martin Houde4,5, Zhi-Yun Li6, Giles Novak7 and

Kwok Sun Tang1

1 The Chinese University of Hong Kong2 Max Planck Institute for Astronomy3 Harvard-Smithsonian Center for Astrophysics4 University of Western Ontario5 California Institute of Technology6 University of Virginia7 Northwestern University

E-mail contact: hbli at phy.cuhk.edu.hk

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The question whether magnetic fields play an important role in the processes of molecular cloud and star formationhas been debated for decades. Recent observations have revealed a simple picture that may help illuminate thesequestions: magnetic fields have a tendency to preserve their orientation at all scales that have been probed - from100-pc scale inter-cloud media down to sub-pc scale cloud cores. This ordered morphology has implications for theway in which self-gravity and turbulence interact with magnetic fields: both gravitational contraction and turbulentvelocities should be anisotropic, due to the influence of dynamically important magnetic fields. Such anisotropy is nowobserved. Here we review these recent observations and discuss how they can improve our understanding of cloud/starformation.

Accepted for publication as a chapter in Protostars and Planets VI, University of Arizona Press (2014)

http://arxiv.org/pdf/1404.2024

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New Jobs

Postdoctoral Fellowship in Star Formation

Applications are invited for a postdoctoral fellowship in observational studies of low-mass star formation. The fellowwill work with Dr. Phil Myers and collaborators on studies of protostar and disk accretion, accretion stopping, andmultiplicity in dense molecular cloud cores. He or she will analyze JVLA and SMA data, and will lead followupproposals to ALMA and other telescopes. He or she will have access to CfA facilities, funds for research and travel,and opportunity to pursue independent research projects.

The position is available starting October 1, 2014, extending for two years, with possible renewal for a third year. Theannual stipend for 2014 is $58,000, plus relocation reimbursement up to $4,000. Smithsonian group health insurancecoverage is fully paid for individuals and families.

The applicant must have a Ph.D. in astronomy, physics, or a related field by the start date. Experience in starformation studies, in observations at millimeter and submillimeter wavelengths, and in interferometry are desirable.To apply, send a pdf package to cores fellow@cfa.harvard.edu, including a cover letter, CV, publication list, and adescription of current research and plans, up to three pages in length. The applicant should arrange for three letters ofreference to be submitted to the same address. Applications received before July 1, 2014 will receive full consideration,but review of applications will continue until the position is filled.

The Harvard-Smithsonian Center for Astrophysics is an Equal Opportunity/Affirmative Action Employer where allqualified applicants receive equal consideration for employment without regard to race, creed, color, sex or nationalorigin.

Postdoctoral Position in Star and Planet Formation

The Department of Physics & Astronomy at the University of Toledo invites applications for a postdoctoral position inthe area of Star and Planet Formation. The postdoc will work with Dr. TomMegeath on a program to study protostarsin the Orion molecular clouds using data from the Spitzer, Herschel, Hubble, and ALMA observatories. A particularfocus will be to work with Hubble and ALMA data that resolve protostellar envelopes and disks. The successfulapplicant will work with Tom Megeath and Will Fischer (now at Goddard Space Flight Center) on existing HST dataand an accepted ALMA program to study edge on protostars. Experience working with radiative transfer codes andmillimeter interferometry will be of great benefit. The postdoc will be part of an international team collaboratingon a comprehensive study of star formation in Orion using infrared and radio telescopes. The University of Toledois a partner in the 4.3 meter Discovery Channel Telescope operated by Lowell Observatory, and the postdoc will beencouraged to submit proposals and use this facility. The appointment will be for two years. Requirements are aPh.D. in astronomy and research experience in star and planet formation.

Please send a cover letter, CV, a statement of research interest up to one page in length, and contact information forreferences to megeath@physics.utoledo.edu by June 15th.

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Summary of Upcoming Meetings

The Formation of the Solar System

13 - 15 May 2014 MPIfR, Bonn, Germanyhttps://indico.mpifr-bonn.mpg.de/theFormationOfTheSolarSystem

The Olympian Symposium on Star Formation

26 - 30 May 2014 Paralia Katerini’s, Mount Olympus, Greecehttp://zuserver2.star.ucl.ac.uk/~ossf14/

EPoS2014 The Early Phase of Star Formation

1 - 6 June 2014 Ringberg Castle, Tegernsee, Germanyhttp://www.mpia-hd.mpg.de/homes/stein/EPoS/epos.php

The Dance of Stars: Dense Stellar Systems from Infant to Old

2 - 6 June 2014 Bad Honnef, Germanyhttp://www.astro.uni-bonn.de/$\sim$sambaran/DS2014/index.html

The Submillimeter Array: First Decade of Discovery

9 - 10 June, 2014, Cambridge, MA, USAhttp://www.cfa.harvard.edu/sma/events/smaConf/

The 18th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun

9 - 13 June 2014 Flagstaff, Arizona, USAhttp://www2.lowell.edu/workshops/coolstars18/

Summer School on Protoplanetary Disks: Theory and Modeling meet Observations

16 - 20 June 2014 Groningen, The Netherlandshttp://www.diana-project.com/summer-school

Workshop on Dense Cores: Origin, Evolution, and Collapse

27 - 30 July 2014 Monterey, CA, USAhttp://www.aas.org/meetings/aastcs4

Characterizing Planetary Systems Across the HR Diagram

28 July - 1 August 2014 Inst. for Astronomy, Cambridge, USAhttp://www.ast.cam.ac.uk/meetings/2013/AcrossHR

Planet Formation and Evolution 2014

8 - 10 September 2014 Kiel, Germanyhttp://www.astrophysik.uni-kiel.de/kiel2014

Living Together: Planets, Stellar Binaries and Stars with Planets

8 - 12 September 2014 Litomysl Castle, Litomysl, Czech Republichttp://astro.physics.muni.cz/kopal2014/

Galactic and Extragalactic Star Formation

8 - 12 September 2014 Marseille, Francehttp://gesf2014.lam.fr

Thirty Years of Beta Pic and Debris Disk Studies

8 - 12 Sepetmber 2013 Paris, Francehttp://betapic30.sciencesconf.org

Towards Other Earths II. The Star-Planet Connection

15 - 19 September 2014 Portugalhttp://www.astro.up.pt/toe2014

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Star Formation Across Space and Time

11-14 November 2014 Noordwijk, The Netherlandshttp://congrexprojects.com/14a09/

45th “Saas-Fee Advanced Course”:

From Protoplanetary Disks to Planet Formation

15-20 March 2015, Switzerlandno website yet

Other meetings: http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

Moving ... ??

If you move or your e-mail address changes, pleasesend the editor your new address. If the Newsletterbounces back from an address for three consecutivemonths, the address is deleted from the mailing list.

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New Books

Exploring the Formation and Evolution of Planetary Systems

Edited by Mark Booth, Brenda C. Matthews, James R. Graham

These are the proceedings of IAU Symposium No. 299 held 2–7 June 2013 in Victoria, British Columbia, Canada.They report on recent results in the field of planet formation and detection and covers the range from the detailedimaging of protoplanetary disks to the modeling of planetary atmospheres.

Recent years have seen a dramatic increase in our understanding of planetary systems. Initially, new exoplanets werediscovered through the effects they have on their parent stars - whether through radial velocity, transits or microlensingmethods - but now the technology and the techniques have been developed to image light from exoplanets directly.Vast improvements have also been made in our ability to resolve circumstellar matter from protoplanetary disks,through transition disks to debris disks. These dramatic new observations have led to new advances in our theoreticalunderstanding of the formation and evolution of planetary systems. The book is up-to-date, and appeared in printonly six months after the end of the meeting.

The following lists the sections of the book:

1 High Contrast AO Imaging: Latest Results in Direct Exoplanet Imaging

2 Peering into Circumstellar Disks: Transformative Interferometry & High Resolution Imaging

3 Building Planets in Protoplanetary Disks: Earliest Evidence

4 Co-evolution of Disks and Planetary Systems

5 Detailed Studies of Known Exoplanets and Exoplanet Systems

6 Debris Disks as Signposts of Planetary Systems

7 Evolution of Planetary Systems

Cambridge University Press 2013, ISBN 9781107045200406 pages, hardcover US$118.75Available from http://http://www.cambridge.org/ua/academic/subjects/astronomy/extrasolar-planets-and-astrobiolog

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Passings

Karen M. Strom

With great sadness we report the passing of Karen M. Strom from a sudden illness.

Karen was a member of the scientific staff of Kitt Peak National Observatory (now part of the National OpticalAstronomy Observatories) from 1972 to 1982. At Kitt Peak she led or contributed to numerous papers on T-Tauristars, their circumstellar disks, envelopes, and outflows, including studies of nebular Herbig-Haro objects. She alsocarried out research on other aspects of stellar evolution, as well as important work investigating the stellar populationsof other galaxies. She, along with her husband Steve and their colleagues, conducted some of the first infrared surveysof star-forming regions. In addition she pioneered early approaches to image processing based on these data. Thatwork contributed to the development of IRAF at NOAO.

From 1983 until her retirement from astronomy in 1998, she was a Research Professor in the Five College AstronomyDepartment (FCAD) at the University of Massachusetts, Amherst, where she continued her scientific work.

As an astronomer Karen is perhaps best known for her estimate of the lifetimes of circumstellar accretion diskssurrounding T Tauri stars in the Taurus-Auriga dark cloud (a fundamental constraint on theories of gas giant planetformation) as well as multi-wavelength studies of the young stellar populations in the L1641 region of the Orion Amolecular cloud and other regions.

Karen was much more than an accomplished scientific researcher and mentor to numerous young scientists. She wasan early innovator on the World Wide Web, and one of its early proponents in academe. She led the development ofone of the first academic departmental websites (highlighting UMass and FCAD astronomy research), and pioneeredhypertext for astronomy research and education (including some of the first digital publishing of PhD dissertations).She also created the first public clickable map for the state of Massachusetts.

After retiring from astronomy, Karen developed websites for Native American artists, consulted on web-based edu-cation, and resumed a long-standing interest in photography. She is publisher or co-publisher of numerous e-books,including ”Sticks and Stones: an alphabet book for the 21st century”, and ”An Armchair Travelers Guide to DeathValley. Her fine art photography is distributed both electronically (of course) and through galleries.

Karen became a world traveler in the service of her art, and recently returned from a travel adventure including stopsin Istanbul, Venice, Barcelona, and Bilbao. She and her husband of 54 years, Stephen E. Strom, dared to take anexcursion over Cappadocia in a hot air balloon. On that trip she took thousands of images that will one day be sortedand compiled by her grandchildren, in her honor.

Karen Marie Lewallen was born in 1941 in Fairfax, Oklahoma and grew up in Henryetta, Oklahoma. She graduatedfrom Harvard College in 1964 (in one of the first classes where women were awarded such a degree), worked at theSmithsonian Astrophysical Observatory and SUNY Stony Brook before moving to Kitt Peak. In 1995 she receivedan honorary Ph.D. in Astronomy from Instituto Nacional de Astrofısica, Optica y Electronica (INAOE) in Puebla,Mexico for her many scientific contributions. She is survived by her husband Steve, daughters Kathy and Julie, andsons Robert and David. She had six grandchildren. Asteroid 4604 Stekarstrom is named in her honor, along with herhusband.

Some of her work can be seen at http://karenstrom.com and glimpses of a rich life shared with others can be foundat http://karenstrom.org.

Lori Allen Michael Meyer David Strom Rob Seaman

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Short Announcements

Planet Formation Imager (PFI) Project – Call for Participation

The Planet Formation Imager (PFI) Kick-off Committee announces an Open Call for Participation in PFI ConceptStudies. The ambitious goal of PFI is to image planet-forming disks in nearby star-forming regions with high enoughspatial resolution to resolve the key physical processes at work, to witness planet formation live as it happens with∼ 0.1AU resolution or better. Scientists from more than a dozen different institutes in six countries have begunplanning for initial Concept Studies, an effort led by Project Director John Monnier (U. Michigan), Project ScientistStefan Kraus (U. Exeter), and Project Architect David Buscher (U. Cambridge). Our top priorities for the next12-24 months will be to define the most exciting areas of science to drive the instrument concept and at the sametime determine feasible architectures for meeting the science goals. We seek contributions from the internationalastronomical community and invite participants to join the PFI Science Working Group or the Technical WorkingGroup. For more information and to sign up to participate, please see http://www.planetformationimager.org (initialdeadline to join working groups is June 16, 2014).

Website: http://www.planetformationimager.orgContact: info@planetformationimager.org

HANDBOOK OF IRON METEORITESby Vagn F. Buchwald

Free Electronic Edition now Available

http://evols.library.manoa.hawaii.edu/handle/10524/33750

The Handbook of Iron Meteorites was originally published by the University of California Press in 1975 for the Centerfor Meteorite Studies at Arizona State University. It has been digitized at the University of Hawaii as it is still anextraordinarily valuable resource and is no longer in print.

This is a monumental book in three volumes containing 1426 pages, 2124 figures, eight appendices and a supple-ment. Volume 1 provides a general introduction to meteorites, fireballs, and impact craters and to the mineralogy,composition, and properties of iron meteorites. It also contains appendices of information about iron meteorites.

Volumes 2 and 3 contain descriptions of about 600 iron meteorites–nearly all those that were known and accessible in1975. These descriptions include information about the structure, mineralogy, and composition of each iron meteorite,its thermal and impact history, discovery and subsequent history, as well as a list of museum holdings. A guide forusers can be found on page 245 at the beginning of Volume 2. At the end of Volume 3 on pages 1376-1418 there isa supplement containing information about eleven meteorites that were studied after 1973 plus additional notes andphotographs for a few other iron meteorites. The original prints for the figures were preserved by Vagn Buchwald andthese have been scanned by the Natural History Museum of Denmark. They can be accessed by figure number:

http://geologi.snm.ku.dk/english/samlinger/meteorit/handbook-iron-meteorites/

Ed Scott, University of Hawaii

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