Title  Physical Structure of Low-mass Star-Forming Cores
Pi     Y. Shirley
Time   120 hrs
1. Name: Physical Structure of Low-mass Star-Forming Cores
    Authors: Yancy Shirley, et al.

 2. Science goal: Map dust continuum emission on a wide range of
spatial scales to probe the density and temperature structure
of the envelope and disk.  Current dust continuum studies suffer
from large uncertainties in the structure of the inner envelope
(R < 1000 AU) and in the size/brightness of accretion disks around 
low-mass YSOs.  The dust continuum should be imaged at submm 
wavelengths since the flux goes as a high power of the frequency 
(S ~ nu^4). A solid understanding of the physical structure (density 
and temperature) of the core is the foundation for all molecular
line radiative transfer studies as well as a understanding of
collapse dynamics.  The sources chosen would have been imaged
at low-resolution with the current generation of mm/submm bolometers
as well as observed with SIRTF.  The initial phase of the project would
image several cores in a range of evolutionary states (and masses)
at 850 microns.  Future studies would attempt to image at higher
frequencies (e.g., 450/350 microns) where questions such as changes
in dust opacity due to differential dust coagulation/ice evaporation 
throughout the envelope and disk may be addressed.


3. Number of sources: 15

4. Coordinates: 

  4.1. 3  sources in Oph      (RA=16:30, DEC=-24)
       3  sources in Perseus  (RA=03,  DEC=+30)
       3  sources in Taurus   (RA=04,  DEC=+25)
       6  sources distributed over sky (RA=any, DEC=any visible)

  4.2. Moving target: no

  4.3. Time critical: no


5.  Spatial scales:

  5.1. Angular resolution: 0.5"
       
  5.2. Range of spatial scales/FOV: 11"x8"

  5.3. Single dish: yes
 
  5.4. ACA: yes

  5.5. Subarrays: no
 

6. Frequencies:

  6.1. Receiver band: Band 7

  6.2. Line: N/A
       Frequency: N/A 

  6.3. Spectral resolution (km/s): N/A
  
  6.4. Spectral coverage (km/s or GHz): Widest bandwidth possible    


7. Continuum flux density:

  7.1. Typical value: 10 - 100 mJy (disks)

  7.2. Continuum peak value: a few hundred mJy (inner envelope)

  7.3. Required continuum rms: 0.002 K (but require full tracks
				        - see Note1)

  7.4. Dynamic range in image: 


8. Line intensity:

  8.1. Typical value: N/A

  8.2. Required rms per channel: N/A
  
  8.3. Spectral dynamic range: N/A


9. Polarization: NO


10. Integration time per setting: 15 x 8 hrs 

11. Total integration time for program: 120 hr


Note 1: 8 hrs per source are required to sufficiently cover 
u,v plane.  Need a large number of visibilities over a wide range
of u,v-distance to reconstruct physical structure of the core.

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Review John Richer: see program 2.1.1.










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Review v2.0:
 
init_7 = 2.1.7

1. Name: Physical Structure of Low-mass Star-Forming Cores
    Authors: Yancy Shirley, et al.

Unchanged w.r.t. DRSP 1.1. ACA will be critical here, and calibration
should be careful to make sure that no spurious "breaks" are created
in the inferred density / temperature profiles. It is noted that 8 hrs
are required to fill the uv-plane. This is not true for ALMA. With 50
antennas the uv-plane is filled quite rapidly, and detailed
simulations are required to determine when it is filled
sufficiently. Multi-frequency observing may be a better strategy to
fill in missing spacings.