high-resolution disks observations

Gaspard Duchêne - Circumstellar disks and planets - Kiel - May 26-28 2010

HIGH-RESOLUTION DISKS

OBSERVATIONSGaspard DuchêneUC Berkeley – Obs. Grenoble


Outline The big questions and how to answer them Scattered light imaging (sub)mm interferometric mapping A few ‘exotic’ approaches Questions still to be solved Future instrumentation and the role of long-

baseline interferometry


The big questions Can we empirically constrain the process of

planet formation? What are the successive stages?

What is the structural evolution of disks?Where does planet formation occur?What are the associated timescales?How do disks dissipate?

Which disks will form planets?Important to compare to exoplanets surveys


High-resolution techniques Scattered light imaging

Optical: HSTNear-IR (1-5μm): ground-based AORequires coronagraphy: mask central regionsEnables polarization mapping




Thermal emission mapping (submm/mm/cm)SMA, PdBI, eVLA, CARMA, ATCAEnables gas mapping




Thermal emission mapping (submm/mm/cm)SMA, PdBI, eVLA, CARMA, ATCAEnables gas mapping

Explicitly excluding IR interferometry here


Complementary approaches

Scattered lightPAH imaging

Thermalimaging

IR interferometry


Outline The big questions and approaches Scattered light imaging (sub)mm interferometric mapping A few ‘exotic’ approaches Questions still to be solved Future instrumentation and the role of

long-baseline interferometry


Scattered light imagingCourtesy M. Perrin


Scattered light imaging Image the outer disk surface

Estimate disk size/inclinationProbe the overall flaring geometry

Burrows etal. (1996)

Krist et al.(2000)

TW Hya



Estimate disk size/inclinationProbe the overall flaring geometryProbe grain size/composition

Honda et al. (2009)

Duchêne et al. (2004)

GG Tau

HD 142527



Estimate disk size/inclinationProbe the overall flaring geometryProbe grain size/compositionIdentify large-scale asymmetries (nature?)

Fukagawaet al. (2004)

Grady etal. (2001)

AB Aur HD 100546


Scattered light imaging Polarized imaging is a key asset

It alleviates the contrast problemIt provides physical information that helps

disentangling dust properties from disk structure

Apai et al. (2004)

Oppenheimeret al. (2008)

Silber etal. (2000)

GG Tau

AB AurTW Hya


Main results from scattering Outer disks are flared, consistent with

hydrostatic equilibrium (good coupling)



hydrostatic equilibrium (good coupling) Dust grains in the surface are not much

larger than ISMamax ~ 1mm strongly excluded (amax < 10μm)



hydrostatic equilibrium (good coupling) Dust grains in the surface are not much

larger than ISMamax ~ 1mm strongly excluded (amax < 10μm)

Departures from asymmetry are commonSpiral arms, gaps, dimples…Warp, variable illumination effects


Limitations of scattering No view of planet-forming region

Masked region: 40-100 AURequires extrapolation inwards




Limited sensitivity to fine-scale structureSpatial resolution: 5-10 AU





Ambiguous interpretation of substructuresSurface density features or local H0 features?





Ambiguous interpretation of substructuresSurface density features or local H0 features?

Over half of known disks are undetected!No apparent SED criterion for detectability


Thermal continuum mapping

Andrews &Williams (2007)


Thermal continuum mapping Image the outer disk midplane

Estimate disk sizeEstimate extent of grain growth (up to ~cm)

Kitamura et al. (2002) Natta et al. (2007)



Estimate disk sizeEstimate extent of grain growth (up to ~cm)Image surface density substructures

Piétu etal. (2005)

Hughes etal. (2009)

AB Aur GM Aur



Estimate disk sizeEstimate extent of grain growth (up to ~cm)Image surface density substructuresConstrain the Σd profile

Andrews &Williams (2007)

Kitamuraet al. (2007)


Gas mapping Map simple species in warm outer disk

Enable dynamical analysis of central starServe as basis for chemistry modelingConfirm gas/dust coupling in asymmetries

Piétu etal. (2005)

AB Aur


Main results from mm mapping Best results from highest

spatial resolution Non-power law structure:

Relatively flat overall profileTapered-off outer regionAccounts for gas/dust obs.

Quite different from MMSN! Much like similarity solution

Isella etal. (2009)


Main results from mm mapping Deficit of dust emission in inner regions

is an unexpectedly common occurrence No counterpart in gas!

Guilloteau etal. (2008)

Isella etal. (2010)

RY Tau

HH 30


Limitations of mm mapping Limited ability to resolve substructures

Linear resolution: ≥ 30 AU Requires extrapolation inwards




Innermost region is optically thick




Innermost region is optically thick Limited sensitivity

Focus on brightest disks for high resolution




Innermost region is optically thick Limited sensitivity

Focus on brightest disks for high resolution Model-dependent results!

Not enough resolution elements for data to guide modeling (apart from peculiar cases)


Some more ‘exotic’ datasets PAH imaging around Herbig Ae stars

Geometry of illuminated outer diskPoorer angular resolution (λ=3-11μm)A proxy to scattering, less contrast-limited

HD 97048PDS 144N

Lagage et al. (2006)Perrin et al. (2006)


Some more ‘exotic’ datasets Spectro-astrometry of hot gas

Can reach ~1mas resolutionCO detected in most disks!

Gas found within inner holes Enables dynamical studies

Pontoppidanet al. (2008)


Some more ‘exotic’ datasets Time domain: periodic occultation

Can probe all the way to the inner radiusWarp/wall in innermost diskCan probe long-term dynamics

Occurrence rate: ~30% !?

Bouvier et al.(1999, 2007)

P=8.2d


How about the inner disk?? The formation zone of most known

exoplanets is believed to be <10 AU What is the structure of disks on that scale? How do the inner and outer disk relate to

each other? How bad are the current extrapolations?

What is the link between planet formation and disk dissipation?


How about the inner disk?? Some predictions/hypotheses to be tested:

Accretion geometry on central star/binaryPuffed-up rim and associated shadowed regionGas within the inner rimPlanet-induced gapsSnow line with pile-up of larger grains/bodiesEmpty (?) holes in transition disksRole of inner disk for undetected outer disks


How about the inner disk?? Some predictions/hypotheses to be tested:

Accretion geometry on central star/binaryPuffed-up rim and associated shadowed regionGas within the inner rimPlanet-induced gapsSnow line with pile-up of larger grains/bodiesEmpty (?) holes in transition disksRole of inner disk for undetected outer disks

We need to image the inner disk


Future instrumentation Next Generation AO on 8-10m telescopes

NICI, SPHERE, GPI, HiCIAO, …Same resolution, much higher contrastLimited to the brightest young starsRegion within 10-20 AU still blocked out


Future instrumentation Next Generation AO on 8-10m telescopes

NICI, SPHERE, GPI, HiCIAO, …Same resolution, much higher contrastLimited to the brightest young starsRegion within 10-20 AU still blocked out

AO on 30-40m telescopes (E-ELT, TMT, …)Higher resolution (~2 AU)Uncertain image qualityPlanet-forming region still out of view (?)


Future instrumentation ALMA

Much higher spatial resolution (~0.5 AU)Much improved image fidelityInnermost regions optically thick, especially at the

shortest wavelengths (best resolution)


Future instrumentation ALMA

Much higher spatial resolution (~0.5 AU)Much improved image fidelityInnermost regions optically thick, especially at the

shortest wavelengths (best resolution) JWST

PSF stability enables HST-like work in the mid-IRProbe of 1-10μm dust grains (rarely doable now)Limited spatial resolution (~40 AU)


The realm of interferometry For most disks: 0.15 AU ≅ 0.001”


The realm of interferometry For most disks: 0.15 AU ≅ 0.001” Large number of baseline critical Many beams across the image needed

We need empirically-based input to improve our general understanding and detailed modeling




Large dynamical range required




Large dynamical range required Sensitivity key to survey broad samples




Large dynamical range required Sensitivity key to survey broad samples Inner disk midplane is out of reach!

Optically thick at all wavelengths

high-resolution disks observations

Documents

planets kiel

circumstelalr disks

structural evolution

exotic approachesquestions

big questionscan

process of planet formation

solvedfuture instrumentation

gg tauhd