Title Infall toward protostars Pi A. Wootten Time 900 hrs 1. Name of program and authors Infall toward protostars [2.2.4 in DRSP 1.1] A. Wootten 2. One short paragraph with science goal(s) Detect molecular line absorption against the continuum of a disk surrounding a protostar. The program is based on the detection of formaldehyde at 1.3 mm in IRAS4A by Di Francesco et al. 2001, ApJ 562, 770. Using IRAM, they detected H$_2$CO absorption at 1.3 mm of $T_b = 10$ K against a continuum of 3000 mJy with a velocity resolution of 0.16 km/s. This provides the best evidence for infall, but it is currently only possible for the few brightest sources. To generalize the result and to study the infall velocity field in detail, we would like to do similar experiments on 30 sources with 10 times weaker disks with a velocity resolution of 0.05 km/s. 3. Number of sources 30 YSOs 4. Coordinates: 4.1. Rough RA and DEC 10 sources in Oph (RA=16:30, DEC=-24) 10 sources in Perseus (RA=03, DEC=+30) 10 sources distributed over sky (RA=any, DEC=any visible) 4.2. Moving target: no 4.3. Time critical: no 4.4. Scheduling constraints: (optional) None 5. Spatial scales: 5.1. Angular resolution (arcsec): 0.5" 5.2. Range of spatial scales/FOV (arcsec): 0.5" to 11" single field 5.3. Required pointing accuracy: (arcsec) 2" 6. Observational setup 6.1. Single dish total power data: beneficial Observing modes for single dish total power: Nutator switch 6.2. Stand-alone ACA: beneficial 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: beneficial 6.4. Subarrays of 12m baseline-ALMA antennas: no 7. Frequencies: 7.1. Receiver band: Band 3, 4, 5, 6, 7, 8, 9 7.2. Lines and Frequencies (GHz): Line: 2 freqeuncy settings in B4 4 freqeuncy settings in B6 7 frequency settings in B7 H2CO 3_12 - 2_11 Frequency: B6 226 GHz and 211 GHz. multiline H2CO 2-1 K=1, K=0 B4: 140 and 145 GHz multiline H2CO 4-3 K=2, K=1, K=0 B7: 362736.0480 363945.8940 364103.2490 364103.2490 364275.1410 364288.8840 365363.4280 GHz multiline 7.3. Spectral resolution (km/s): 0.08 km/s @ B6 7.4. Bandwidth or spectral coverage (km/s or GHz): 20 km/s 8. Continuum flux density: 8.1. Typical value (Jy): .3 Jy 8.2. Required continuum rms (Jy or K): 0.2 mJy 8.3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether, e.g., weak objects next to bright objects) 8.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) repeatability ( 1-3% / 5% / 10% / n/a ) relative ( 1-3% / 5% / 10% / n/a ) 9. Line intensity: 9.1. Typical value (K or Jy): 0.03 Jy 9.2. Required rms per channel (K or Jy): 0.1 K 9.3. Spectral dynamic range: 20 9.4. Calibration requirements: absolute ( 5% ) repeatability ( 1-3% ) relative ( 1-3% ) 10. Polarization: no 10.1. Required Stokes parameters: 10.2. Total polarized flux density (Jy): 10.3. Required polarization rms and/or dynamic range: 10.4. Polarization fidelity: 10.5. Required calibration accuracy: 11. Integration time for each observing mode/receiver setting (hr): 10 hr 12. Total integration time for program (hr): 30 x 3 x 10 = 900 hr 13. Comments on observing strategy : (optional) B4: The K=1 and K=0 lines lying at 140839.5020 & 145602.9490 GHz lie within the 4 GHz range of the B4 receiver and are to be observed with one correlator setting. B6: I would choose dual polarization no cross products, 8 digitizers of 125 MHz bandwidth giving 2048 channels across each placement of the digitizers. I would place these on the lines specified in this DRSP but within the expected 8 GHz bandwidth of the B6 receiver, I could also cover other lines. I would choose the 3(0,2)-2(0,2) line at 218.222 GHz, the 3(2,2)-3(2,1) line at 218.475 GHz, the 3(1,2)-2(1,1) H213CO line at 219.908 GHz and the primary target the 3(1,2)-2(1,1) H2CO line at 225.698 GHz, on each of which would be placed a digitizer pair. Note that in the latest System Technical Specs, the IF of B6 was lowered to 4.5-10 GHz but that it is expected to be capable of meeting specs across the range of the spectral lines proposed for observations (Webber and Effland, private communication). B7: The lines chosen lie within the 4 GHz range of the B7 receiver with one correlator setting. -------------------------------------------------- Review v2.0: In the course of preparation of DRSP version 2, I have reviewed your DRSP (2.2.4) entitled: "Infall toward protostars", and I have a following minor comment. This is an important program making full use of the ALMA capability. It is not very clear for me why multiple lines of H2CO (and its isotopomers) be observed. Probably some information on the infalling structure can be derived? A sentence describing this may be helpful. Furthermore it may be useful to prioritize the observing bands. ---------------------------------------------------------------------- Reply: Recall the proposed settings: H2CO 3_12 - 2_11 Frequency: B6 226 GHz and 211 GHz. multiline H2CO 2-1 K=1, K=0 B4: 140 and 145 GHz multiline H2CO 4-3 K=2, K=1, K=0 B7: 362736.0480 363945.8940 364103.2490 364103.2490 364275.1410 364288.8840 365363.4280 GHz multiline Since the optical depths of these lines will vary, the structure of the infalling gas should be derivable from the variation of its optical depth with frequency (and velocity excursions/lineshape). For example, Choi claimed that the absorption seen by DiFrancesco in the 226 GHz line occurred in a low excitation sheet of material which overlay the star forming region. If so, this sheet should not be detectable for instance in the higher excitation lines in B7 and would have greater optical depth in the low lying B4 lines. In reality, it is unlikely a single physical state exists in the absorbing material, and we would want to characterize its density structure by utilizing the many transitions H2CO offers. The plan is similar to the deconstruction of the column to a protostar used by Hurt, R. L., Barsony, M., & Wootten, A. 1996, apj, 456, 686 and similar objects in naughtily unpublished data. Each band has several lines which might be observed with a single correlator setting. Possibly, the settings for B6 would be sufficient, with next priority B4 then B7.