Title Energetics of the HH 80-81 molecular outflow Pi D. Shepherd Time 325 hrs DRSP 2.0, re-submittal of DRSP 1.1 project 2.2.6 1. Name: Energetics of the HH 80-81 molecular outflow. Authors: D. Shepherd et al. 2. Science Goal: HH 80-81 is a well-collimated jet powered by an intermediate mass young stellar object with a spectral type later than B1. It is the most massive star which powers a well-collimated, parsec-scale jet similar to those produced by low-mass young stellar objects. The ionized jet has a projected length of about 5 pc (Marti, Rodriguez, & Reipurth 1993; Heathcote et al. 1998). The truncated CO flow (mass ~ 460 Msun) full opening angle is roughly 40 deg and does not re-collimate (Yamashita et al. 1989). The dynamics of the jet suggest that it is a scaled-up version of a T Tauri star jet. The CO flow position angle is misaligned with the jet by roughly 30deg and it is unclear if the observed jet can power the CO flow. However, the only CO measurements that exist were done with less than Nyquist spacing, 15'' resolution, and the authors assumed the emission was optically thin. These factors place a large uncertainty on the known dynamics of the CO flow and its relationship to the ionized jet. To determine the total mass and dynamics in the molecular flow we would like to image the HH 80-81 molecular outflow in three spectral lines (12CO(J=2-1), 13CO(J=2-1), & C18O(J=2-1). The aims are to recover all emission in the flow in the CO isotopes to estimate optical depth and energetics, and trace high velocity emission to specific regions. The continuum emission between 230 & 219 GHz will be used to get the millimeter SED of the driving source(s) as well as other sources detected in the region at 6cm. The mosaic must be sensitive to size scales between 1" and 60" in the outflow, thus, ACA and Total Power measurements are absolutely required to recover the extended emission. Multi-scale reconstruction of the combined uv-data will be needed to generate the final mosaic images. 3. Number of Sources: 1 field of 15'x15' 4. Coordinates: 4.1 Central coordinates: 18 19 12.11 -20 47 30.4 (J2000), (Galactic coordinates: LII= 10.8415 BII= -2.5916) mosaic region: 15'x15' centered on above coordinates 4.2 Moving target: No 4.3 Time Critical: No 4.4. Scheduling constraints: (optional) None 5. Spatial Scales: 5.1 Angular Resolution (arcsec): 1" 5.2 Range of spatial scales/FOV (arcsec): 1" to 60" large mosaic FOV: 15'x15' 5.3. Required pointing accuracy: (arcsec) 0.6" High pointing accuracy is required for accurate mosaic imaging with this band 6 30" primary beam. 0.6" should be achievable with reference pointing. 6. Observational setup 6.1. Single dish total power data: required Observing modes for single dish total power: Position switch in on-the-fly mapping mode 6.2. Stand-alone ACA: no 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: beneficial 6.4. Subarrays of 12m baseline-ALMA antennas: ? Not clear what this means. This project requires 3 subarrays: 1 for the ALMA 12m array, 1 for the ACA 7m array, and 1 for the ACA 12m TP antennas. 7. Frequencies: 7.1 Receiver Band: 6 7.2 Lines: Main lines of interest = CO isotopes (e.g. CO(J=2-1), 13CO(J=2-1), C18O(J=2-1)) Frequencies (GHz): 230 GHz, 220 GHz, 219 GHz (lines listed are the main lines of interest, other will also be observed). CO will be observed in the USB while 13CO & C18O will be observed in the LSB simultaneously. 7.3 Spectral Resolution (km/s): 0.3 km/s 7.4 Spectral Coverage (km/s or GHz): 200 km/s per line 8. Continuum flux density: 8.1 Typical Value: 0.5-10 mJy 8.2 Required Continuum RMS: 0.03 mJy (to detect primary driving source of the flow as well as any lower-mass YSOs in the cluster) 8.3 Dynamic Range within Image: > 20 There is expected to be bright, large-scale (>30"), diffuse emission with faint, small scale and/or extended emission overlaid or very close to the brighter emission. This will be a complicated imaging experiment. 8.4 Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) 5% repeatability ( 1-3% / 5% / 10% / n/a ) 5% relative ( 1-3% / 5% / 10% / n/a ) 5% Continuum is not the highest priority science here. It will be important to see where the continuum emission is located and derive mass estimates based on that emission. But assumptions inherent in the mass calculations will be far greater than this 5% uncertainty. What will be important is that the continuum and background sources must be subtracted from the final image. For this, it is important to make sure the continuum errors have the same order of uncertainty as the line emission. 9. Line Intensity: 9.1 Typical value: > 10 Jy at 12CO line peak 10-100 mJy in high velocity wings 9.2 Required RMS per channel: 15 mJy/beam 9.3 Spectral Dynamic Range: > 10 9.4 Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) 5% repeatability ( 1-3% / 5% / 10% / n/a ) 1-3% relative ( 1-3% / 5% / 10% / n/a ) 5% While absolute calibration and relative calibration between spectral lines in this band do not require extremely high accuracy, I think that the repeatability is another issue. This is a LARGE mosaic and if the line flux densities between different segments of the mosaic (taken on different days) and/or different observations of the same field (12m array & ACA) have significantly different flux densities, this will compromise the accuracy of the final mosaic deconvolution. 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): 11.1 Integration time per field for the ALMA array (interferometric and total power observations): Assuming a multi-field mosaic, 50 antennas, 30" primary beam, 15'x15' mosaic, 4 beams/arcmin => 60x60beams = 3600 fields (just less than Nyquist spaced). 15 mJy/beam RMS in each field => 2 min integration on each field (0.3 km/s resolution) x 3600 fields = 120 hrs. Because fields will overlap, we will gain roughly a root 2 increase in sensitivity over the mosaic region. Integration time = 120/sqrt(2) hrs = 85 hrs. Note on overhead: we will likely have to do several passes through the mosaic to collect the total 2 min integration required for each field. This will increase the overhead beyond what calibration and slew times require. The 12CO(2-1) line will have to be observed separately from 13CO and C18O. Doing them all at one time may mean that one polarization will have to be sacrificed ==> lowered sensitivity. This is not acceptable. Thus, 2 mosaics will have to be made, each requiring 85 hrs of total integration time. 11.2 The ACA interferometer will require 4 times more integration to achieve a similar RMS to the ALMA array but the primary beam is larger: 50" primary beam, 15'x15' mosaic ==> 36x36 beams = 1296 fields (just less than Nyquist spaced). 2x4min integration/field = 173 hrs/sqrt(2) = 120 hrs. 11.3 ACA 12m total power dishes: The extended emission in this cloud will be significantly brighter than the compact, more high-velocity, outflow emission. Nominally it should be adequate to get total power data with the same integration time as the 12m interferometer. However, this source is near the galactic plane and in a region rich with CO emission. The Total Power mosaic will likely need to be larger than the interferometer mosaic to ensure that the edge of the mosaic has emission-free regions (required to spatially smooth the image across the scanning direction to remove artifact stripes that may be present due to changes in the atmosphere between observing OFF positions). As a guess, say the 12m TP integration time will be the same as the ACA interferometer (larger mosaic, less integration time on each field). 12. Total integration time for program (hr): In summary, this project requires: * 85 hours of 12m array time * 120 hours of ACA interferometer time. * 120 hours of ACA TP time (see note in sect 11.3 for details). (Overhead is not included in this estimate.) 13. Comments on observing strategy : (optional) (e.g. line surveys, Target of Opportunity, Sun, ...): This project must obtain a larger mosaic in Total Power than the field needed to be covered by the interferometer. Actual size of the TP mosaic is uncertain (here I assume it will take 4 times longer than the 12 array to make this larger TP mosaic). For efficiency, the ACA TP antennas should be controlled in a separate subarray, ---------------------------------------------------------------- Note that this band 6 project observes CO, 13CO & C18O simultaneously. It is equally important to and valid to observe these same isotopes in other bands/transitions. However, time estimates change dramatically because all isotopes cannot be observed at the same time. Thus: Band 3, 12co and 13co(1-0) separated by about 5.1 GHz ==> must have 2 different spectral setups. Band 7: 12co and 13co(3-2) separated by about 15.2 GHz ==> this will barely fit into the USB/LSB spread but c18o(3-2) cannot be observed at the same time. Thus, you still need 2 separate tuning, one for 12co and one for 13co/c18o. Band 8: 12co and 13co(4-3) separated by 20.2 GHz ==> must have 2 different spectral setups. Band 9: 12co and 13co(6-5) separated by 30 GHz ==> must have 2 different spectral setups. All other bands that propose to observe these isotopic ratios will require double the time than this proposal. -------------------------------------------------- Review v2.0: 2.2.6 Shepherd Energetics of the HH 80-81 outflow Personally I think this map is far too large for an ALMA project and that the other proposals are a much better way to do this but undoubtedly this type of project will be accomplished by ALMA