Sub-mm Interferometry of Protoplanetary Disks (aka

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Sub-mm Interferometry of Protoplanetary
Disks(aka Heterodyne Arrays 101)
1
?
ALMA
HD 141569 HST ACS
Geoffrey A. Blake, Caltech
Ringberg Disks Meeting
16Apr2004
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Talk Outline

• How do heterodyne arrays work?
• - Strengths versus weaknesses.
• What can we do now?
• - Dust versus lines.
• III. Will things improve soon?
• - SMA and CARMA.
• Disks in the ALMA era.
• - What will be needed for ALMA to exploit
• its full potential?

16Apr04
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Spectroscopy of Disk Atmospheres
G.J. van Zadelhoff 2002, Ph.D. thesis
300 30 3 K
Chiang Goldreich 1997

IR disk surface within several
several tens of AU (sub)mm disk surface
at large radii, disk interior
16Apr04
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Arrays everywhere!
PdBI
VLA
BIMA
SMA
ATCA
OVRO
Typically ntel 6-10.
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The 1-Baseline Heterodyne Interferometer

• HST resolution at 1mm D10 km! Use
  array.
• Cant directly process 100 1000 GHz signals.
• Heterodyne receivers detect V and f, noise
  defined by the quantum limit of hn/k.
• Positional information is carried by the PHASE.
• Spectral coverage depends on the receivers, while
  the kinematic resolution is determined by the
  correlator.

Geometrical delay
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The 1-Baseline Heterodyne Interferometer

• B varies due to earth rotation.
• The convolving internal is 2D, and defines the
  minimum (u,v) cell size. Note the minimum
  baseline is at least D !
• Single baseline noise
• in Jy (A aperture, J Jy/K for single
  telescope, hQ correlator efficiency, Dn
  frequency interval, t on-source time).

16Apr04
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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 qS)-2

qP primary telescope beam
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n-Element Imaging
(1)
F.T., convolve (Dirty image)
CLEAN or MEM deconvolution
(2)
Dirty Beam
NGC 1333 IRAS2

• is linear,
• is not.
• So, error analysis is
• difficult in the image plane!

OVRO
BIMA
Jørgensen et al. (2004)
16Apr04
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Sub-mm Arrays Star Formation
outflow
x1000 in scale
infall
Cloud collapse
Rotating disk
Planet formation
Mature solar system
Sufficiently large sub-mm arrays can examine all
phases and radii.
Adapted from McCaughrean
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Tailored Imaging
By varying the (u,v) coverage, or weighting, the
effective resolution (and flux recovery) can be
adjusted for large objects. Disks in true
protostars?
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OVRO CO(2-1) Survey of T Tauri stars
(Koerner Sargent 2003)

• 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)

See also Dutrey, Guilloteau, Simon, Ohashi
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Disk Ionization Structure CO and Ions
Disk properties vary widely with radius, height
and depend on accretion rate, etc. (Aikawa et al.
2002, w/ DAlessio et al. disk models).
Qi et al. 2004
Currently sensitive only to Rgt80 AU in gas
tracers, Rlt80 AU dust. CO clearly optically
thick, other species likely to be as
well. The surface fractional ionization is
gt10-8, easily sufficient for MRI transport.
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Chemical Imaging of Outer Disk?
Qi et al. 2004 in prep
HDO formed via H2D, possible tracer of H3?
Kessler et al. 2004, in prep
CO well mixed, while CN/HCN traces enhanced
UV fields. Is LkCa 15 unusual?
Photodesorption?
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Disk Molecular Distribution Models
LkCa 15 HCN observations
Ro50AU
Ro300AU
Ro100AU
Ro200AU
Image fidelity presently limited by (u,v)
coverage, sensitivity.
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Future of the U.S. University Arrays CARMA
CARMA OVRO (6 10.4m) BIMA (9 6.1m) SZ Array
(8 3.5m) telescopes.
March 27, 2004
SUP approved! 2004 SZA at OVRO 2004 move
6.1m 2004 move 10.4m 2005 full operations

Cedar Flat 7300 ft.
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Disk Observations w/CARMA
Dust
Md0.01Msun Rout120AU Rhole20AU
HDO rms (3sigma) 0.05-0.1 K
(CARMA w/D config. in 5 hrs, many OVRO
transits)
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Disks with inner holes? TW Hydra w/SMA
CO 3-2
CO 2-1
Qi et al. 2004, ApJL, in press.
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Transitional/Debris Disks? HD141569 Vega
w/PdBI
Vega, Wilner et al. 2002
CO 2-1 from HD141569 J.-C. Augereau A. Dutrey
astro-ph/0404191
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Planets are born well inside 50-100 AU
Planetary velocities are considerable, however,
should we use spectroscopy or imaging (or both)?
Theory
Jupiter (5 AU) V_doppler 13 m/s V_orbit 13
km/s
Simulation G. Bryden, JPL
Observation?
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Enter ALMA
Dust simulation (L.G. Mundy), unrealistic phase
errors, but no CLEAN/MEM.
Superb site large array exceptional
performance (64 12m telescopes, by 2012).
Llano de Chajnantor 5000 m, good for astronomy,
tough for humans!
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Atmospheric Phase Correction (mm Adaptive Optics)

• Atm. fluctuations (mostly
• H2O) can vary geom. delay.
• Veif decorrelation
• if Efgtp (each baseline).
• If the fluctuations vary
• systematically across the
• array, phase errors ensue.
• Problem is NOT solved.

OVRO WLM System
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Sub-mm Interferometry of Disks - Conclusions
(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. Can ions, e.g. N2H and
esp. H2D, save the day? New/combined arrays
(SMA, CARMA ALMA) will provide access to much
smaller scales, lines/dust may selectively
highlight regions of planet
accretion/formation. With present arrays, the
nonlinear nature of image reconstruction
algorithms means that analysis is best done in
the (u,v) plane. Not so with ALMA. For ALMA to
achieve its potential, active phase correction
schemes MUST be developed. This is analogous to
multi-conjugate AO (HARD!).
16Apr04
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Poster Summary IR Spectroscopy Disks
Keck
R10,000-100,000 (30-3 km/s) echelles
(ISAAC,NIRSPEC, PHOENIX,TEXES) on 8-10 m
telescopes can now probe typical T Tauri/Herbig
Ae stars
CO M-band fundamental

NIRSPEC R25,000
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What about other species?
NGC 7538 IRS9

Boogert et al. 2004, ApJ, in press
16Apr04
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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 mm photons
  to much larger distances.

Blake Boogert 2004, ApJL 606, L73.
16Apr04