(sub)mm & infrared spectroscopy of circumstellar disks geoffrey a. blake div. geological &...
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(Sub)mm & Infrared Spectroscopy of
Circumstellar Disks
Geoffrey A. BlakeDiv. Geological & Planetary Sciences
59th OSU Symposium 25June2004
HD 141569A (HST ACS)
People Really Doing the Work!
Caltech: -Jacqueline Kessler (now at UT Austin), Joanna Brown -Adwin Boogert, Chunhua Qi (now at the SMA/CfA)
Leiden w/Ewine van Dishoeck & Michiel Hogerheijde: -Klaus Pontoppidan, Gerd Jan van Zadelhoff, Wing-Fai Thi (now at ESO)
25June2004
I. Why study disks?II. Mm-wave interferometry of protoplanetary disks.III. High resolution IR spectroscopy of disks.IV. Conclusions
Cloud collapse Rotating disk
infall
outflow
Planet formation Mature solar system
x1000 in scale
Adapted from McCaughrean
How are isolated Sun-like stars formed?
Picture largely derived from indirect tracers, especially SEDs.
Spitzer Space Telescope
- IRAC (mid-IR cameras, 3.6 4.5, 5.8, 8.0 m) - MIPS (far-IR cameras, 24, 70 160 m, R=20 SED mode) - IRS (5-40 m long slit,R=150, 10-38 m echelle, R=600)
August 2003 launch, >5 year lifetime.
- GTO observations
- Legacy program
- General observations25June2004
Evans et al., c2d~170 YSOs first look + follow up of mapping.
Meyer et al.Photometry~350 sources, IRS follow up (Class III).
Boogert et al. 2004, ApJS special issue
25June2004
HH 46 w/IRAC, IRS
Ices toward young low mass stars
Keck/VLT+Spitzer
Study Isolated Disks (Weak/No Outflow)
25June2004
Beckwith & Sargent 1996, Nature 383, 139-144.
Planet building phase
Why study disks? Star-disk-planet interactions:
Radial velocity surveys aresensitive to ~Jupiter/Saturnmass planets out to >5 AU.From whence hot-Jupiters?
Disk-star- and protoplanet interactions lead to migration while the disk is present.
The answer lies at earlier times…
Theory
Observation?
1 AU at 140 pc subtends 0.’’007.
Jupiter (5 AU):V_doppler = 13 m/sV_orbit = 13 km/sSimulation G. Bryden
Spectroscopy of “Disk Atmospheres”
25June2004
IR disk surface within several – several tens of AU(sub)mm disk surface at large radii, disk interior
G.J. vanZadelhoff2002
Chiang &Goldreich 1997
The 1-Baseline Heterodyne Interferometer:
•HST resolution at 1mm D=10 km! Use array.•Can’t directly process 100 – 1000 GHz signals.•Heterodyne receivers detect |V| and , noise defined by the quantum limit of h/k.•Positional information is carried by the PHASE.•Spectral coverage depends on the receivers, while the kinematic resolution is determined by correlator.
25June2004
Geometrical delay
The n-Element Heterodyne Interferometer:
•n(n-1)/2 baselines, imaging performance depends on the array geometry, but•For small to moderate n, the (u,v) plane is sparsely filled.•For a given array, the minimum detectable temperature varies as (resolution = S)-2 :
25June2004P = primary telescope beam
CO 3-2 CO 2-1
CO traces disk geometry, velocity field:
Qi et al. 2004, ApJL, in press.TW Hydra w/SMA
Disk properties vary widelywith radius, height; and depend on accretion rate,etc. (Aikawa et al. 2002, w/D’Alessio et al. disk models).
Currently sensitive only to R>80 AU in gas tracers, R<80 AU dust.
CO clearly optically thick, isotopes reveal extensive depletion, poor mass tracer!
The fractional ionization is >10-8, easily sufficient for MRI transport. HD & H2D+
(Ceccarelli et al. 2004) in midplane?
Disk Ionization Structure: CO and Ions
CO well mixed, while [CN]/[HCN] traces enhanced UV fields.Is LkCa 15 unusual?
Photodesorption?
Qi et al. 2004 & in prep
Chemical Imaging of Outer Disk?
HDO formed via H2D+, possible tracer of H3
+?
Kessler et al. 2004, in prep
(6 transits)
Ro=50AU Ro=300AURo=200AURo=100AU
For models: Using scaled H density distribution with varying inner radius cutoff
R0 Rout
NT
LkCa 15 HCN observations
Molecular Distribution Models
CO 2-1 from HD141569J.-C. Augereau & A. Dutrey astro-ph/0404191
Transitional/Debris Disks? HD141569 & Vega w/PdBI:
Vega, Wilner et al. 2002
Future of the U.S. University Arrays – CARMA
CARMA = OVRO (6 10.4m) + BIMA (9 6.1m) + SZ Array (8 3.5m) telescopes.
SUP approved!2004 SZA at OVRO2004 move 6.1m2004 move 10.4m2005 full operations
Cedar Flat 7300 ft. June 15th, 2004
March 27th , 2004
(pre-ALMA) The size scales are too small even for the largest current & near-term arrays. Spectroscopy to the rescue!
How can we probe the planet-forming region?
Theory
Observation?
Jupiter (5 AU):V_doppler = 13 m/sV_orbit = 13 km/s
High Resolution IR Spectroscopy & Disks
CO M-band fundamental
Keck
NIRSPECR=25000
R=10,000-100,000 (30-3 km/s) echelles (ISAAC,NIRSPEC, PHOENIX,TEXES)on 8-10 m telescopes can now probe“typical” T Tauri/Herbig Ae stars:
AB Aur
HD 163296
L1489:Gas/Ice~10/1, accretion.
CRBR2422.8:Gas/Ice~1/1, velocity field?
Elias 18Gas/Ice<1/10(Shuping et al.)
Edge-on absorption.
Orientation is Pivotal in the IR!
H2, H3+ in absorption?
25June2004
Spitzer Enables the Study of Edge-on Disks!
25June2004
VLT VLT
ISAACS
Flu
x (J
y)The small molecules in ices are similar in protostars and disks.
What about other species w/echelles?
25June2004
NGC 7538 IRS9
Boogert et al. 2004, ApJ, in press
Edge-on Disks & Comets?
IR studies of edge on disks will map out both gas phase & grain mantle composition, compare to that found in massive YSOs, comets.
N7538 W33A Hale-BoppWater 100 100 100CO 10 1 23CO2 16 3 6CH4 1 0.7 0.6H2CO 3 2 1CH3OH 9 10 2HCOOH 2 0.5 0.1 NH3 10 4 0.7OCS 0.1 0.05 0.4
25June2004
CO lines give distances slightly largerthan K-band interferometry, broad H I traces gas much closer to star (see also Brittain & Rettig 2002, ApJ, 588, 535;Najita et al. 2003, ApJ, 589, 931).Can do ~30-40 objects/night.
In older systems, CO disk emission is common:
Herbig Ae stars, from~face-on (AB Aur) to highly inclined (HD 163296).
CO lines correlated with inclination and much narrower than those of H I Disk!
Pf
Systematic Line Width Trends:•Objects thought to be ~face on have the narrowest line widths, highly inclined systems the largest.•As the excitation energy increases, so does the line width (small effect).•Consistent with disk emission, radii range from 0.5-5 AU at high J.•Low J lines also resonantly scatter 5 m photons to much larger distances.•Asymmetries (VV Ser)?
25June2004Blake & Boogert 2004, ApJL 606, L73.
CO and 13CO rotation diagramsshow curvature as a result of >1. Still, small amounts of gas since N(H2)~5 x 1022 leads to dust opacities near unity.
Collisional excitation important, but cannot explain line widths at low J values (too broad). Resonant IR scattering at larger radii!
The vibrational excitation is highly variable, likely due to variations in the UV field. Disk shadowing?
How is the CO excited in these disks?
25June2004
CO
13CO
Explanation:
Dust sublimation near the star exposes the inner disk to direct stellar radiation, heating the dust and “puffing up” the disk.
Flared disk models often possess 2-5 micron deficiency in model SEDs, where a “bump” is often observed for Herbig Ae stars.
Where does the CO emission come from?
Dullemond et al. 2002
25June2004
Calvet et al. 2002
For dust sublimation alone, the lines from T Tauri disks should be broader than those from Herbig Ae stars+disks. Often observed, but…
CO Emission from Disks around T Tauri Stars
The TW Hya lines are extremely narrow, even for a disk with i~7 degrees, imply R>2 AU. Gap tracer?
(Sub)mm-wave instruments can only study the outer reaches of large disks at present in lines; even at these wavelengths the disk mid-plane is largely inaccessible due to molecular depletion.
Expanded arrays (CARMA, eSMA, ALMA) will provide access to much smaller scales, lines should selectively highlight regions of planet accretion/formation. Midplane w/H2D+?
High resolution IR spectroscopy just starting, is immensely powerful, and provides unique access to the 0.5-50 AU disk surface before advent of ALMA, large IR interferometers. Spectra are esp. sensitive to disk geometry.
Spitzer is providing beautiful spectrophotometric SEDs and many new targets!
Disk Spectroscopy - ConclusionsDisk Spectroscopy - Conclusions
25June2004
AB Aur
HD 163296
Arrays everywhere!
25June2004
PdBI
VLA
SMABIMA
OVRO
ATCA
Typically ntel ≤ 6-10.
Embedded disks?
Padgett et al 1999
3mm: HCO+, HCN, 13CO, C180 (1-0) 2000 AU radius, 0.02 M disk 1mm: HCO+ (3-2) infall (disk not quite fully rotationally supported) 0.65 M M 1.4 M disk collapse to 300 AU in 2 x 104 yrs?
L1489, a disk in transition?
HCO+ 3-2 HCO+ 1-0
See also:Hogerheijde etal 1997, 1998;Looney 2000;Chandler & Richer2000, Shirley et al2000
Hogerheijde 2001
OVRO CO(2-1) Survey of T Tauri stars
• stellar ages 1 - 10 Myrs
• stellar masses ~ 1 M
• selection by 1 mm flux, SED characteristics
• Taurus 19/19 detections
• Ophiuchus 4/6 detections
• resolution ~ 2”
20 objects
radii 150 AU
masses 0.02 M
(from SEDs)
(Koerner & Sargent 2003)
See also Dutrey, Guilloteau,& Simon, Ohashi
Chemical / Radiative Transfer ModelingPhysical model: D'Alessio et al. 2001Chemical model: Willacy& Langer 2001Radiative transfer: Hogerheijde & vander Tak 2000
Molecular line surveyUV fieldsgrain reactions disk ages and evolution
Understanding Disk Chemistry
MM-Wave CO Traces Dynamics, Others?
25June2004
Dutrey et al. 1997, IRAM 30m
D. Koerner & A. Sargent OVRO, in
Qi et al. (2004).
Measure:R_diskM_starInclination
w/resolvedimages.
LkCa 15LkCa 15
The Sample (drawn from larger single dish + OVRO CO survey):
Star Sp Type d(pc) Teff(K) R(Rsun) L(Lsun) M(Msun) Age(Myr) LkCa 15 K5:V 140 4365 1.64 0.72 0.81 11.7 GM Aur K5V:e 140 4060 1.78 0.8 0.84 1.8HD 163296 A0 120 9550 2.2 30.2 2.3 6.0 MWC 480 A3 130 8710 2.1 32.4 2.0 4.6
Mannings, Koerner & Sargent 1997Mannings, Koerner & Sargent 1997
MWC 480
LkCa 15
Koerner & Sargent 1995
OVRO+CSO/JCMT MM-Wave Disk Survey
25June2004
Combine 3/1.3 mm array images w/higher J spectra to
constrain OUTER disk properties, chemical networks.
van Zadelhoff et al. 2001
OVRO+CSO/JCMT MM-Wave Disk Survey II
25June2004
Source L* (L ) CN/HCN H
dust/h
gas
LkCa 15 0.72 ~ 10 1.0GM Aur 0.80 << 1 4.0 MWC 480 30.2 ~ 4 1.7 HD 163293 35.2 >> 50 -
[CN]/[HCN] traces enhanced UV fields (Fuente et al. 1993,
Chiang et al. 2001)
Molecular distribution ring-like?
Photochemistry or desorption?
Qi et al., in prep
UV Fields: HCN and CN
LkCa 15
25June2004
Infinite resolution, complete UV coverage
Observed UV sampling, uniform weighting
CO 2-1 fitLkCa15 ___model - - -
Model Parameters i = 58°, Vturb= 0.1 km/s Ro= 5 AU, Rout= 430 AU nCO = 10-4 nH (D'Alessio 2001) syn = 3.6” x 3.6”
3.05.0 4.3 3.7
8.28.99.5
5.6
6.36.97.6
Modeling the effects of (uv) Sampling
MM-continuum surveys do not reveal such large, massive disks in similarly aged clusters (IC348) and clouds (NGC 2024, MBM12). Environment?
Need better (sub)mm-wave imaging capabilities. SMA! and…
CO, HCO+ (and NNH+) chemistry well predicted by disk models.
Other species, esp. CS, CN, HCN, much more intense, with unusual emission patterns in some cases (LkCa 15).
Are these large disks unusual?
29Aprn03
CARMA – Site Monitoring
HDO: rms (3sigma) = 0.05-0.1 K (CARMA w/D config. in 4 hrs)
ALMACARMA
Md=0.01Msun Rout=120AU Ro=20AU
Disk Observations w/CARMA+ALMA
Dust simulation (L.G. Mundy), unrealistic phase errors, but no CLEAN/MEM.
•Atm. fluctuations (mostly H2O) can vary geom. delay.•|V|eif decorrelation if Ef>each baseline).•If the fluctuations vary systematically across the array, phase errors ensue.•Problem is NOT solved.
OVRO WLM System
Atmospheric Phase Correction (mm Adaptive Optics)
Enter ALMA:
Llano de Chajnantor; 5000 m, good for astronomy, tough for humans!
Superb site & large array exceptional performance (64 12m telescopes, by 2012).
Dust simulation (L.G. Mundy), unrealistic phase errors, but no CLEAN/MEM.
Ices in the disk of L1489 IRS
• Prominent band of solid CO detected toward L1489, originating in large, flaring disk.
• CO band consists of 3 components, explained by laboratory simulations as originating from CO in 3 distinct mixtures:
1 'polar' H2O:CO
2 'apolar' CO2:CO [NEW!]
3 'apolar' pure CO(Boogert, Hogerheijde & Blake, ApJ 568,761, 2002)
Nearly all spectra observed to date have emission from very high J levels (J>30-35), but…
Variations in CO M-band Spectra:
25June2004
The degree of vibrationalexcitation is highly variable!
This model can now be directly tested via YSO size determinations with K-band interferometry.
Intense dust emission pumps CO, rim “shadowing” can produce moderate T_rot.
Fits to AB Aur SED yield an inner radius of ~0.5 AU (and 0.06 AU for T Tau).
SED Fits versus IR Interferometry
(Monnier & Millan-Gabet 2002, ApJ)
Dullemond et al. 2002
Many other species and disk types (transitional, debris, etc.) should be examined in both absorption (edge-on disks) and emission, but extremely high dynamic range will be needed.
Protoplanet tracers?H2, H3
+, CH4, H2O, OCS... Line profile asymmetries?
Future “Near”-IR (1-5 m) Spectroscopy
Brittain & Rettig 2002, Nature