ALMA View of Dust Evolution: Making Planets and Decoding ...• GM Aur, TW Hya, CoKu Tau 4, DM Tau,...

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1 ALMA View of Dust Evolution: Making Planets and Decoding Debris David J. Wilner (CfA) Grain Growth Protoplanets Debris

Transcript of ALMA View of Dust Evolution: Making Planets and Decoding ...• GM Aur, TW Hya, CoKu Tau 4, DM Tau,...

Page 1: ALMA View of Dust Evolution: Making Planets and Decoding ...• GM Aur, TW Hya, CoKu Tau 4, DM Tau, … – near/mid-ir flux deficits indicate inner holes – planet formation? viscous

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ALMA View of Dust Evolution: Making Planets and Decoding Debris

David J. Wilner (CfA)

Grain Growth → Protoplanets → Debris

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“Protoplanetary” to “Debris” Disks

• <1 to ~10 Myr• gas and trace dust

– gas dynamics (hydro, turbulence)

– ~0.001 to 0.1 M

• excess: near/mid/far-ir/mm• dust particles are sticking,

growing into planetesimals

• up to Gyrs• dust and trace gas

– dust dynamics (radiation, collisions)

– <1 Mmoon

• excess: mainly far-ir/mm• planetesimals are colliding

and creating dust particles

SM

A Isella et al. 2006

CSO Marsh et al. 2005

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Disk Dust and ALMA

• longest observable λ’s: 0.35 to >3 mm• “vibrational” emission is dominant mechanism

(thermal fluctuations in charge distribution)• unprecedented sensitivity, resolution, calibration

• sensitive to “cold” dust: T<10’s of K• if low opacity, then flux ~ Mdust weighted by Tdust

• wavelength dependence of mass opacity diagnostic of particle properties, esp. grain size

• no contrast problem with stellar photospheres

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• collisional growth– subµm to mm sizes stick at <1 m/s

– • from m to km sizes?

– too large for chemistry, too small for gravity– collective effects, e.g. layers? vortices? spiral waves?

Blum et al. 1998, 2000C. Dominik

SiO2

The Beginning: Particles Stick

QuickTimeª and aYUV420 codec decompressor

are needed to see this picture.

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• dust mass opacity model, e.g. power law• flux density emitted by disk element dA

• mm data: disk β~0 to 1 (large grains) vs. ISM β~2 (Rayleigh limit)• concern with optically thick contribution

Spectral Signatures of Growth

Pollack et al. 1994 mixture, compact, segregated spheres, n(a) ~ a-q, q=3.5

Calvet & D’Alessio 2001

amax=1 mm

amax=10 cm

Beckwith & Sargent

1991

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• combine physical model, fluxes, resolved data– irradiated accretion disk (Σ~r-1,T~r-0.5) matches

(a) SED and (b) resolved 7 & 0.87 mm continuum – shallow mm slope and low brightness require amax > 1 mm

Example: TW Hya

β=0.7±0.1

Qi et al. 2004, 2006

Calvet et al. 2002

VLA 7 mm

SMA 0.87 mm

SED

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Many Resolved Disks, β Measures

ATCA 3mm Lommen et al. 2006

VLA/PdBI/OVRO Natta et al. 2004

solid: Lommen et al. 2006 (10 southern pms stars)dashed: Rodmann et al. 2006 (10 Taurus pms stars)dotted: Natta et al. 2004 (7 Ae stars + TW Hya, CQ Tau))

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ALMA: Resolved Disk “Colors”• precision subarcsec spectral index information

– couple with disk structure models to account for opacity and temperature variations, localize grain growth

S. Andrews

no growth

“inside-out”grain growth

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Millimeter Sizes Persist Myrs

• much longer timescale than <<0.1 Myr theory predicts

• competition between growth and destruction processes?

• grain size (opacity) need not follow a simple power law

• are the disks we can study in the millimeter the ones that will never form planets? – probably not: transition disks

Weidenschilling 1997

Dullemond & Dominik 2005

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• all indicators of circumstellar material decline, t ~ 5 Myr• GM Aur, TW Hya, CoKu Tau 4, DM Tau, …

– near/mid-ir flux deficits indicate inner holes– planet formation? viscous evolution and photoevaporation?

Calvet et al. 2005

“gap”

inner disk with bit of ~µm dust

r~24 AU inner edge of outer disk

Bryden et al. 1999

Transition Disks

~2 Myr, M*=0.84, Md~0.09 M

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Example: GM AurCO 2-1 IRAM PdBIDutrey et al. 1998

Schneider et al. 2003

230 GHz IRAM PdBI

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Debris Disks

• discovered in far-ir:– ~15% of main sequence

stars show “debris”: IRAS, ISO, Spitzer

• ~10 disks imaged in scattered light and/or thermal emission– highly structured– inner holes, clumpy

rings, warps, spirals, offsets, asymmetries

– sculpted by planets?

Holland et al. 1998 Greaves et al. 1998

Smith & Terrile 1984

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no planets planets

– KB dust drifts in– clumpy ring around

orbit of Neptune; 3:2 → two clumps (cf. “Plutinos”)

– nearly empty inner hole due to Jupiter

Liou & Zook 1999

Resonant Perturbations• Pres = Pplanet (p+q)/p, planet gives periodic kicks • structure created when resonances filled by

– inward migration of dust due to P-R drag– outward migration of planet traps planetesimals

• e.g. simulation of dust in our Solar System:

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Large Dust ≠ Small Dust• structure depends on Frad/Fgrav

– largest grains retain resonant parent distribution– intermediate grains librate widely, smooth out – smallest grains are unbound, blown out

3:2Wyatt 2006

VegaH

olland et al. 1998

Su et al. 2005

850 µm70 µm 24 µm

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Example: Vega (350 Myr, A0V, 7.8 pc)

• like Neptune migration (Wyatt 2003)?�∆a ~7 AU over ~50 Myr (Hahn & Malhotra 1999)

QuickTimeª and aYUV420 codec decompressor

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Wyatt 2003

Minor Planet Centerwhite: 2:1 Plutinos

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• sensitivity limited with existing facilities• the archetype Vega at 1.3 mm

– compatible images (poor SNR and uv coverage)– dust blobs are robust, spatially extended– stellar photosphere (2 mJy) provides calibration check

Higher Angular Resolution?

IRAM PdBI: Wilner et al. 2002 OVRO: Koerner et al. 2001

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• Vega is north (+38 dec) but visible with ALMA

An ALMA Simulation

thanks to J. Pety

• compact configuration: 2x1 arcsec @ 350 GHz

• low surface brightness (model) disk emission– mosaic essential– ACA essential– total power essential– careful treatment of

bright star (5 mJy) in imaging and deconv.

• high fidelity challenging for large, nearby disks

model image

fidelitydifference

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Synoptic Studies

• resonant structures rotate around star

• multi-epoch imaging– follow motions of

clumps to distinguish models (and exgal. background sources)

– Vega: a circular Neptune or an eccentric Jupiter?

∀ ε Eri rotation ~1”/yr detected (2σ)? (Greaves et al. 2005)

see Wilner et al. 2002 and Moran et al. 2004

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Planet Parameter Space

• debris disk structure probes long periods

• complementary to classical techniques

period→←m

ass

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Summary

• ALMA will qualitatively change nature of dust observations from disks, all evolutionary stages

• Protoplanetary Disks– grain growth from

resolved “colors”• Transition Disks

– image holes, etc.• Debris Disks

– locate planets with resonant particles

– fossil record of planet dynamics

QuickTimeª and aYUV420 codec decompressor

are needed to see this picture.

NASA/ R. Hurt