Molecular surveys in 2-3 ``small'' samples from 0.5 to 3 msun
  Authors: A.Dutrey, M.Momose, S.Guilloteau, E. van Dishoeck

  2. Science goal:
         Study observable chemistry as complete as possible in a few
protoplanetary disks
  orbiting stars from 0.5 to 3 msun. The goal is to estimate abundance 
gradients, within
  the disk and from object to object. It is required to disentangle 
between excitation
  conditions and abundance gradients by observing several transitions of 
the same molecule.
  A frequency survey AS COMPLETE AS possible - using all the
flexibility of
  the correlator - is required.

    The sensitivity required to complete such a survey is not easy to 
derive. As a first
    order, one can note that lines detected so far become optically 
thick inside a radius
    R1 ranging from 50 to 300 AU.  With a power law of the surface 
density, a line with
    Tau=1 at 50 AU has Tau=0.07 at 300 AU. We thus select to work at
an opacity limit of
    0.05 (1 sigma per channel). Moreover, we include a few much deeper
integrations in Band 6 to reach tau=0.02 and search for more complex molecules.
We select an angular resolution of 
0.4", allowing to
    partially resolve the optically thick core (60 AU at 150 pc).

  3. Number of sources: 6

  4. Coordinates:
    4.1. 3 sources in Taurus    (RA=04:30, DEC=+30)
         3  sources in Oph      (RA=16:30, DEC=-24)
    4.2. Moving target: no
    4.3. Time critical: no

  5.  Spatial scales:
    5.1. Angular resolution: 0.4 arcsec
    5.2. Range of spatial scales/FOV: up to 8 arcsec
    5.3. Single dish: no
    5.4. ACA: no
    5.5. Subarrays: no

  6. Frequencies:
    6.1. Receiver band: Band 3, 6, 7, 9
    6.2. Lines: see table below as (an incomplete) example
    6.3. Spectral resolution (km/s): 0.2km/s
    6.4. Spectral coverage (km/s or GHz): ~30-40 km/s disk

  7. Continuum flux density: see also 3)
    7.1. Typical value: 50-200 mJy
    7.2. Continuum peak value:
    7.3. Required continuum rms:
    7.4. Dynamic range in image:

  8. Line intensity:
    8.1. Typical value: opacity limit of 0.05 at Tk=10--40 K, i.e.
0.5--2 K (deeper integration down to tau=0.02 for Band 6)
    8.2. Required rms per channel: 0.5 K (deeper for Band 6)
    8.3. Spectral dynamic range: low (in each channel...)

  9. Polarization: not in this proposal

  10. Integration time per setting:
    Band 3: rms 1.7 K per hour, 12 hours per tuning, 2 tunings, 24 hours
    Band 6: rms 0.4 K per hour, 3.3 hour per tuning, 3 tunings, 10 hours
    Band 7: rms 0.5 K per hour, 1 hour per tuning, 3 tunings, 3 hours
    Band 9: rms 0.3 K per hour, 0.4 hour per tuning, 3 tunings, 1.2 hours

    Total: 38 hours per source, of which 14 at Band 6 and above.

  11. Total integration time for program:
    For 6 sources, 229 hours.


Column density with 1K km/s for each transition under LTE and
optically thin condition (Courtesy of Takakuwa at CfA) Line
transition    Frequency  20 K              50 K HCO+  1-0
89.188    1.39407967E+12   2.94454009E+12 CS  2-1    97.981
5.70174978E+12   1.11192032E+13 C18O  1-0    109.782
1.30730522E+15   2.70087115E+15 13CO  1-0    110.201
1.29839255E+15   2.68121637E+15 CO  1-0    115.271
1.1979902E+15    2.45996908E+15 C18O  2-1    219.560
5.3351956E+14    8.22277114E+14 13CO  2-1    220.399
5.30987708E+14   8.16971591E+14 CO  2-1    230.538
5.0249783E+14    7.57216339E+14 CS  5-4    244.935
3.56575535E+12   3.07323687E+12 HCO+  3-2    267.558
4.27181797E+11   4.91656758E+11 C18O  3-2    329.331
5.16935379E+14   4.99454013E+14 13CO  3-2    330.588
5.1608577E+14    4.96851068E+14 CS  7-6    342.883
8.32157289E+12   2.88205239E+12 CO  3-2    345.796
5.07081138E+14   4.67465531E+14 HCO+  4-3    356.734
5.62513526E+11   3.88788454E+11

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Review Phil Myers:transitions proposed for observation include only CO 
and CS isotopomers, thus may not "completely" study "observable 
chemistry" in disks--no  N species are included. 

Comment Ewine: Above table by Takakuwa is only illustrative for a few
dominant species. Many more molecules can be covered in one correlator
setting.