Title Structure and collapse of protostellar envelopes Pi J. Richer Time 240 hrs 1. Name: Structure and collapse of protostellar envelopes Authors: J Richer 2. Science goal: Make good resolution images of a sample of protostars in continuum and line emission. The goals are to test dynamical models of cloud collapse, and trace the accretion flow from envelope to disk, without resolving in any detail the disk structure. Moderate mosaicing is required, and good small/zero spacing measurements. Continuum and line emission both equally important to this study. The observing stategy outlined here is make large images at 3mm, smaller ones at 1mm and smaller still at 450 microns as we expect the line emission to get more compact at higher frequencies. 3. Number of sources: 10 4. Coordinates: 4.1. 5 Class 0 sources in Oph (RA=16:30, DEC=-24) 5 Class 0 sources in Taurus (RA=03, DEC=+30) 4.2. Moving target: no 4.3. Time critical: no 5. Spatial scales: 5.1. Angular resolution: 0.5 arcsec 5.2. Range of spatial scales/FOV: A) 100 arcsec at 3mm B) 40 arcsec at 0.85mm C) 15 arcsec at 0.45mm 5.3. Single dish: yes 5.4. ACA: preferably 5.5. Subarrays: no 6. Frequencies: A) 6.1. Receiver band: Band 3 6.2. Line: HCO+ 1-0 and/or H13CO+ isotope in stronger sources. f=89 GHz 6.3. Spectral resolution (km/s): 0.05 km/s 6.4. Spectral coverage (km/s or GHz): 10 km/s B) 6.1. Receiver band: Band 7 6.2. Line: HCO+ 4-3 and/or H13CO+ isotope in stronger sources Frequency: 367 GHz 6.3. Spectral resolution (km/s): 0.05 km/s 6.4. Spectral coverage (km/s or GHz): 20 km/s C) 6.1. Receiver band: Band 9 6.2. Line: ? TBD, perhaps CO 6-5 isotope, HCN - no time to check freqs... Frequency: 650GHz 6.3. Spectral resolution (km/s): 0.05 km/s 6.4. Spectral coverage (km/s or GHz): 20 km/s 7. Continuum flux density: 7.1. Typical value: 7.2. Continuum peak value: 7.3. Required continuum rms: 7.4. Dynamic range in image: 8. Line intensity: 8.1. Typical value: 8.2. Required rms per channel: 1 K 8.3. Spectral dynamic range: 10 9. Polarization: no 10. Integration time: A) 4x4 mosaic, 30 minutes per pointing B) 4x4 mosaic, 30 minutes per pointing C) 4x4 mosaic, 30 minutes per pointing 24 hours per source, 11. Total integration time for program: 240 hr Notes ************************************************************************ Review Munetake Momose: This is a plan to observe protostellar envelopes at three different frequencies with an identical rms level in line brightness and velocity resolution, though the mapping area is larger at lower frequencies. Such strategy requires more observing time for lower frequencies because (Tb dv) is proportional to (lambda ^3) for the same flux density and dv, but this plan does not take it into account. As a result, the required integration time at 90GHz is severely underestimated (by a factor of ~10). Although it's not clear whether all the regions of an envelope should be mapped with an identical rms level in line brightness, the outer regions must have lower temperature/density and narrower velocity width, hence the brightness sensitivity of ~ 1K and velocity resolution of ~0.05 km/s are crucial in the 90 GHz observations, as stated in the plan. To fulfill the scientific goal within a reasonable observing time, I believe the requirement for the beam size at 90 GHz can be relaxed by a factor of ~2. Since the protostellar collapse would proceed in a "self-similar" way, angular resolution in linear scale is less important when one observes outer regions of the envelope at lower frequencies. If we take 0.9" as the beam size of the 90 GHz observations, 30-minute integration is sufficient to achieve 1 K rms at the velocity resolution of 0.05 km/s, and we don't have to change the total integration time. Concerning about the observed line in Band 9, which is not clearly specified in the plan, I also agree that it is still unclear which line is appropriate and that we should remain it TBD. -------------------------------------------------- Review v2.0: ok