Title  Gaps in nearby protoplanetary disks
Pi     S.Guilloteau
Time   13 hrs


Gaps in nearby protoplanetary disks
==================================
  
Authors: S.Guilloteau, A.Dutrey

  2. Science goal: image gaps created by protoplanets in nearby dust
protoplanetary disks. The goal is to measure the gap radius and the 
brightness contrast gap/disk in order to constrain hydrodynamics
models of planet formation in disks. See also predictions by Wolf et
al., 2002. We have to image to a significant
brightness level at the highest possible angular resolution. For a
proto-Jupiter, the gap width is about 1-2 AU. The highest possible
angular resolution (0.013", i.e 1.8 AU at 140 pc) is therefore
required. The proposed observed frequency is 345 GHz, high enough to
provide high angular resolution, but not too high because otherwise
even the gap would be optically thick to dust emission. At 5 AU from
the star, the dust opacity at 345 GHz will be of order 8 to 20, but
since the surface density contrast is expected to be of order 100, the
gap will still be optically thin.

 A secondary goal would be to detect ``CO gaps'' in these disks at the 
sensitivity limit provided by the main goal (the continuum).

  3 Number of sources: 5 objects

  4.Coordinates:
    4.1
      2 sources in Taurus   (RA=04, DEC=+25)
      1 in Hya (TW Hya) (RA=11, DEC=-34)
      2 sources in ChaI     (RA=11, DEC=-70)
    4.2 Moving target: no
    4.3 Time critical: no

  5.  Spatial scales:
    5.1. Angular resolution: 0.035 arcsec
    5.2. Range of spatial scales/FOV: up to 1 arcsec
    5.3. Single dish: no
    5.4. ACA: no
    5.5. Subarrays: no

  6. Frequencies:
    6.1. Receiver band: Band 7
    6.2. Lines: CO (3-2) line
         Frequency: 345 GHz
    6.3. Spectral resolution (km/s): 1 km/s
    6.4. Spectral coverage (km/s or GHz): >=100 km/s

  7. Continuum flux density:
    7.1. Typical value: N/A
    7.2. Continuum peak brightness: 50 - 200 K
    7.3. Required continuum rms: 1 K
    7.4. Dynamic range in image: > 100:1

  8. Line intensity: sensitivity limited by continuum goals
    8.1. Typical value: 50 - 200 K (optically thick)
    8.2. Required rms per channel: N/A
    8.3. Spectral dynamic range: N/A

  9. Polarization: no

  10. Integration time per setting:
    rms in continuum : 1.6 K in 1 hour, so 2.6 hours required.
    in line. Note that this gives at 1 km/s resolution a
    brightness rms of 80 K.

  11. Total integration time for program:
      5 sources at 2.6 hours = 13 hours

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Review Phil Myers: for gap imaging, candidate disks should be more nearly 
face-on than edge-on, authors do not say how they would select 
face-on candidates (other than TW Hya). Time requested is remarkably 
short -- a bargain!


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Review v2.0:
 
Gaps in nearby protoplanetary disks
==================================
  
Authors: S.Guilloteau, A.Dutrey

Reviewer:  J. Bally

I would add higher frequency data as well.  Thought it is possible
that gaps may become optically thick, we do not know for sure. The
highest possible resolution should be sought for in this experiment.
Furthermore, I would expect that the inner edge of a gap may be in
shadow, and therefore colder than the outer edge which may be
illuminated, and therefore warmer.

Planets opening gaps are expected to be surrounded by circum-planetary
disks and spiral waves.  These features may be picked-up by the
highest resolution ALMA images of the closest sources.

Accreting proto-giant planets are also expected to have photospheres
nearly an AU in diameter.  ALMA may directly detect such objects as
compact point sources within a gap.  They may be hotter than
surrounding dust due to accretion heating.