Title  Protoplanetary disks in Orion 
Pi     J. Williams
Time   90 hrs
1. Name of program and authors
   Protoplanetary disks in Orion
   Jonathan Williams


2. One short paragraph with science goal(s)
   Primary goal is to mosaic the Trapezium cluster in Orion and map the
   thermal dust continuum emission from protoplanetary disks (proplyds)
   around solar mass stars. Observations should be at submilllimeter
   wavelengths where the dust emission dominates the bremsstrahlung
   from the ionized gas cocoons around the disks.
   Secondary goal is to resolve selected disks to measure surface density
   profiles, possibly detect inner holes, and compare the emissivity with
   10 micron absorption.
   Tertiary goal is to measure the thermal dust continuum at a shorter
   wavelength and determine the frequency dependence of the grain
emissivity.
   There is also the potential to detect rotational and possibly
   vibrational lines from the disk and ionization front but
   the confusion with the background cloud will be high.


3. Number of sources
   There are over 2800 identified cluster members and 74 disks
   seen in silhouette against the HII region background by HST.

4. Coordinates:

4.1. Rough RA and DEC
   The cluster extends roughly 10' in each direction from the O6 star,
   Theta1C at RA 05:35:16.47, Dec -05:23:23.10

4.2. Moving target: yes/no (e.g. comet, planet, ...)
   no

4.3. Time critical: yes/no (e.g. SN, GRB, ...)
   no

4.4. Scheduling constraints: (optional)


5. Spatial scales:

5.1. Angular resolution (arcsec):
   A1. 2'' sufficient to distinguish individual proplyds from each other
       and measure a total mass
   A2. 0.1'' necessary to resolve disks, measure surface density profiles

5.2. Range of spatial scales/FOV (arcsec):
   Proplyds are densely packed, just a few arcseconds away from each
   other toward the cluster center. The entire cluster extends over
   approximately 20'x20'.

5.3. Required pointing accuracy: (arcsec)
   standard


6. Observational setup

6.1. Single dish total power data: no/beneficial/required
   no

6.2. Stand-alone ACA: no/beneficial/required
   no

6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas:
   no

6.4. Subarrays of 12m baseline-ALMA antennas: yes/no
   no


7. Frequencies:

7.1. Receiver band: Band 3, 4, 5, 6, 7, 8, or 9
   Bands 7, 9

7.2. Lines and Frequencies (GHz):
   F1. 345 GHz continuum
       [center on CO(3-2) in LSB, many others in passband including
        HCN(4-3), H13CN(4-3), HC15N(4-3), CH3OH lines]
   F2. 691 GHz continuum
       [center on 12CO(6-5) in LSB, get H13CN(8-7) and CH3OH in pb]

7.3. Spectral resolution (km/s):
   [0.2 km/s]

7.4. Bandwidth or spectral coverage (km/s or GHz):
   8 GHz


8. Continuum flux density:

8.1. Typical value (Jy):
   for Hildebrand kappa_nu = 0.1 cm2/g at 1200 GHz, beta=1, T=20K
   minimum solar mass nebula (MMSN; 0.02 Msun) has flux
   30 mJy (345 GHz) and 200 mJy (691 GHz)
   Disk masses in Taurus with similar ~1 Myr age as Orion average 10% MMSN

8.2. Required continuum rms (Jy or K):
   Aim to detect 0.1 MMSN at 5-sigma
   Rms = 0.6 mJy (345 GHz), 4 mJy (691 GHz)

8.3. Dynamic range within image:
   The cloud-HII interface in the background is several Jy at 850 microns
   To be limited by noise and not the background requires a dynamic range
   > 1000:1

8.4. Calibration requirements: absolute      10%
                               repeatability 5%

                               relative      5%


9. Line intensity:
   The background may be considerably more variable in line emission,
   especially if optically thick, and it is likely to be difficult to
   distinguish proplyd emission. Line detection is therefore a lower
   priority than the continuum measurements as indicated by placing
   observational parameters related to this in square brackets.

9.1. Typical value (K or Jy):
   brightness temperature for optically thick emission = 30 K
   beam dilution in 2'' beam ~ 10 depending on disk inclination

9.2. Required rms per channel (K or Jy):
   [1 K in each band]

9.3. Spectral dynamic range:
   [10:1 for optically thick emission, possibly >1000:1 if thin]


9.4. Calibration requirements: absolute      [10%]
                               repeatability [5%]
                               relative      [5%]


10. Polarization: yes/no (optional)
   no

10.1. Required Stokes parameters:

10.2. Total polarized flux density (Jy):

10.3. Required polarization rms and/or dynamic range:

10.4. Polarization fidelity:

10.5. Required calibration accuracy:


11. Integration time for each observing mode/receiver setting (hr):
   Primary goal to image at 345 GHz at 1-2'' resolution and 0.6 mJy rms
(A1/F1)
   requires 10 seconds per field. Mosaicking the central 20'x20' at 10''
   (Nyquist) spacing of the cluster requires 14400 pointings, corresponding
   to 40 hours (not counting telescope slew times).
   Secondary goal to resolve selected disks (A2/F1) requires 30 minutes
   per object, assuming the flux is spread over 20 beams.
   Tertiary goal to image disks at high frequency (A1/F2) requires
   10 seconds per field. The fov is about half the diameter of the 345 GHz
fov
   so it may be prohibitive to map the entire cluster. To map the central
   10'x10' region, which contains most of the young stars, would require
   40 hours.




12. Total integration time for program (hr):
   To mosaic the entire cluster (20'x20') at 345 GHz,
   the central 10'x10' at 691 GHz, and to resolve 20 disks
   at 345 GHz, requires a total of 90 hours.


13. Comments on observing strategy : (optional)
   Given the large number of pointings and the short integration
   times per field, there may be a significant overhead to add.