Title Molecular surveys in 2-3 ``small'' samples from 0.5 to 3 msun Pi A. Dutrey Time 229 hrs 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 ************************************************************************ 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. -------------------------------------------------- Review v2.0: Molecular surveys in 2-3 ``small'' samples from 0.5 to 3 msun Authors: A.Dutrey, M.Momose, S.Guilloteau, E. van Dishoeck Reviewer: John Bally The Taurus fields are far north. Sources in Cha I or in one of the other southern SFRs would be more appropriate targets. It would be desirable to conduct full spectral scans of one or more entire windows to determine the contents of large molecules. The targets should be pre-selected for spectral richness using single-dish observations. These multi-species searches could trace the "snow-lines" for various species - at what radii do they disappear from the gas phase? If gaps or other disk structures are seen, do molecular abundances vary from the shadowed to the illuminated sides of gaps? Reply: You are too optimistic, the abundant molecules are already known, from single-dish obsevrations. Unfortunately, even with the ALMA sensitivity (eg see for example our PPV revieW), the chance to detect the snow-line is very very low... Idem for the shadowed to illuminated sides of gaps... Disks around double stars such as L1551 IRS5 which has both circumstellar and circumbinary disks should also be considered for such studies. Reply: YES, but this is not a proposal