Protoplanetary Disk Science and

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Protoplanetary Disk Science and the Square
Kilometer Array
David J. Wilner Harvard-Smit
hsonian Center for Astrophysics

• Relevance of Protoplanetary Disks
• planet formation, accretion physics
• Disks are Naturally multi-l Objects
• driver for JWST/ALMA/TMT, etc.
• New Regime for SKA
• direct imaging of dust emission
• in realm of rocky planets, track
• secular changes in disk structure

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Stages of Planetary System Formation
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Planet Building

• How do planets form? What accounts for the
  diversity of planetary
• systems? How common are Solar Systems like our
  own?
• Observe young stellar systems to identify
• 1. physical processes (e.g. grain growth,
  orbital migration)
• 2. signatures of planets in formation (gaps in
  disks)
• There are large numbers (100s) of
  protoplanetary disks at 140 pc size scale of
  regions relevant for planets is lt 10 AU, i.e. 70
  mas
• (protoplanetary means enough gas to form giant
  planets)

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Next Generation High Resolution Imaging
ALMA dust emission q 13 mas x (345 GHz/18
km) (and molecular line emission at much lower
resolution) TMT scattered light q 13 mas x
(1.6 mm/30 m) (and infrared spectroscopy that
probes inner disks indirectly) SKA (low t) dust
emission q 1 mas x (24 GHz/2000 km) long ls
have advantage of low opacity to penetrate inner
disks for rms 10 K at q 1 mas, need rms 10
nJy
TW Hya
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State-of-the-Art Disk Images
TW Hya _at_56 pc
Hubble Space Telescope optical scattered light
(Schneider et al. 2001)
Very Large Array 7mm dust emission (Wilner et
al. 2000) SKA resolution will be better by 100x
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Physical Models of Disk Structure

• physical models now
• taking place of power law parameterizations

• self-consistent treatment
• of radiative and hydro-
• static equilibrium using
• 11D radiative transfer

S(r)
T(r)
h(r)
e.g. Chiang Goldreich 1997, 99 DAlessio et
al. 1997, 98 , 99... Dullemond et al. 2000, 01,
02...
for steady a accretionS m/3pn (r3/2Tm) -1
r -p , p 1 (except inner disk)
SED
DAlessio et al. 2001
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Testing Disk Structure Models

• comparison of models with sparse array
• data is often best done in visibility domain

TW Hya SMA 0.87 mm Qi et al., in prep

• Calvet et al. (2002)
• irradiated accretion disk
• model matches SED and
• 7 mm, 0.87 mm images

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TW Hya an eVLA Simulation

• physical model of
• irradiated accretion
• disk adapted from
• Calvet et al. (2002)
• ApJ, 568, 1008
• VLA Pie Town
• configuration, 7 mm
• eVLA could easily
• image 4 AU radius
• hole (if it exists)

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Are Protoplanetary Gaps Detectable?
ALMA
VLTI
Wolf et al. 2002
Brightness distributions from hydrodynamical
simulations of a disk with an embedded Jupiter
mass planet for the VLTI at 10 mm, and for ALMA
at 700 mm. The gap lies 37 mas (5.2 AU) from the
star.
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Evidence for Grain Growth in Disks

• at long ls where tlt1,
• F kdust l-2 l-(b2) , so
• radio/mm data provide
• direct measure of b,
• diagnostic of grain size,
• shape, composition

• compact, spherical particles
• with a ltlt l, b2
• pebbles, rocks, asteroids
• with a gtgt l, b0

Beckwith and Sargent 1991
If F l-2 , then large grains? or compact
structure with tgt1?
resolve ambiguity...
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Example Large Grains in CQ Tau

• CQ Tau
• M 1.5 Mo,
• age 10 Myr
• spectral index
• 1 mm to 7 mm 2.4
• 7 mm emission
• resolved by VLA,
• models indicate
• t lt 1 for r gt 8 AU,
• R 200 AU (p1),
• kdust l-0.6
• most of dust mass
• in cm-size grains

Testi et al. 2003
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Example the DG TAU Protostellar System

• well-studied, very
• active, T Tauri star
• optical jet P.A. 226
• VLAPT at 7 mm
• sees inner dust disk,
• q 35 mas, DK 20
• where is the star? at
• the peak? in the hole?what produces the
• asymmetry? are any
• blobs jet plasma?how does the structure
• change with time?

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SKA could play Unique Role in Disk Studies

• If capable at gt 20 GHz, SKA will have best
  resolution
• for imaging thermal emission.
• For direct detection of structure
• in disks induced by planets,
• sub-AU resolution is key.
• (synergy with other facilities)
• High angular resolution probes
• terrestrial planet region and
• enables following evolution
• over orbital timescales.
• Short centimeter wavelengths
• are critical for tracking grain growth from
  sub-micron
• interstellar size particles to pebbles.

Bate et al. 2003