Title Transitions disks around CTTs/WTTs & near ZAMS stars. Pi A.Bacmann Time 88 hrs 1. Title: Transitions disks around CTTs/WTTs & near ZAMS stars. Authors: A.Bacmann, A.Dutrey 2. Science goal: To detect and map disks having a low flux density in continuum at 1.3mm (<=20-50 mJy) and found around CTTs (Classical TTauri stars), WTTS (Weak line T Tauri stars) and near ZAMS (Zero Age Main Sequence) stars in CO and in the continuum. The observations should allow to determine the disk properties, i.e. the gas disk, extent, disk mass, kinetic temperature, CO depletion with respect to the dust mass. The goal is to understand the dissipation of disks around pre-main sequence stars from 0.5 to 3 msun. 3. Number of sources: Taurus, Rho Oph., Scorpius, Chamaeleon, Lupus - = in total 50 objects 4. Coordinates 4.1. RA & DEC Taurus: RA=04 DEC=+25 - 10 Oph: RA=16:30 DEC=-24 - 20 ChaI: RA=11 DEC=-70 - 20 Lupus: RA=16 DEC=-35 ? Sco: RA=17 DEC=-40? 4.2. moving target: no 4.3. Time critical: no 5. Spatial scales 5.1 angular resolution: 0.3" (resolve disk to first order) 5.2 single field 5.3 total power: no 5.4 ACA no 5.5 subarrays: no 6. Frequencies 6.1 Frequency band: 6 and 7 6.2 Line and Frequencies (GHz) A. 12CO(2-1) 230.5 GHz and 13CO(2-1) 220.4 GHz (if tuning allows) B. 13CO(3-2) 330.6 GHz 6.3 Spectral resolution: 0.2 km/s 6.4 Bandwidth/Spectral coverage: 40 km/s 7. Continuum flux density 7.1 Typical value (Jy) 0.02 Jy 7.2 Required rms 0.1 mJy/Beam 7.3 Dynamic range within image: standard, low 8. Line intensity 8.1 typical value: in 12CO(2-1): 0.1 - 1 Jy.km/s (based on BP Tau) Expected linewidth is 3 - 5 km/s (small sources). 8.2 required rms per channel: 7 mJy (or 2 K in brightness) (about 5 sigma per channel) 8.3 spectral dynamic range 9. polarisation: no (too weak) 10. integration time per setting A. 12CO(2-1) 230.5 GHz and 13CO(2-1) 220.4 GHz (if tuning allows) 10 minutes per source for 12CO(2-1). The continuum sensitivity is 20 microJy. (Note: If a limit on 13CO is needed, 30 minutes per source to get a brightness sensitivity of 1 K; this will NOT be sufficient to detect 13CO in the optically thin sources.) B. Search for 13CO(3-2) in the most interesting sources. 13CO(3-2) opacity is 9/4 / 60 times the 12CO(2-1) opacity, i.e. 0.04 if the 12CO is marginally optically thick. The expected brightness is thus about 20 -- 50 K x 0.04 = 1 -- 2 K. The brightness sensitivity should be around 0.3 K. This requires 8 hours per source. (Note: using the 13CO(2-1) line, the needed sensitivity is 0.13 K, and requires 36 hours per source). 11. total integration time for program: A. Search for 12CO 50 x 10 minutes = 8 hours B. 13CO on the 10 most interesting sources = 80 hours Total = 88 hours. ***************************************************************************** Review Phil Myers: I suspect that more than 8 hours will be needed to detect 12CO 2-1 from most of the sample, especially the older members which will have a lot less gas than does the BP Tau disk. -------------------------------------------------- Review v2.0: 1. Title: Transitions disks around CTTs/WTTs & near ZAMS stars. Authors: A.Bacmann, A.Dutrey Reviewer: John Bally This should be a two-step program: First, detect disks with a compact configuration of AMLA that delivers a roughly 1" beam that is matched to the expected source diameter. Second, obtain high-resolution images of the best detected sources with a resolution of 0.1" to characterize the line and continuum emission. It is unclear if CO and its isotopes will be the best tracers of transition disks. I would expect that most CO will have frozen out or been processed into other compounds. On the other hand, it is also possible that rare isotopic variants (13CO, C18O, or C17O) may be better tracers than CO. Before large amounts of observing time are spend on observing many targets in these lines, a few selected objects should be subjected to an extensive spectral line search to identify the best tracers of the gas phase. I would not be surprised if some molecular ions or other exotic species served to trace the gas better.