Title Structure and starformation of LMC/SMC molecular clouds Pi S. Aalto Time 630 hrs 1. Name of program and authors: Structure and starformation of LMC/SMC molecular clouds Aalto, Johansson, Rubio, Tatematsu, Black, Viallefond 2. One short paragraph with science goal(s): The Magellanic Clouds provide unique possibilities to study the effects of metallicity and radiation field on the structure of the the interstellar medium (ISM). For example, there is tentative evidence that the interstellar molecular gas in the Magellanic Clouds is characterized by a higher degree of clumping than is the case in the Galaxy. This is suggested to be an effect of reduced dust abundances and, accordingly, a deeper penetration of the UV radiation into the ISM, producing strong photodissociation of the molecular species. So far, SEST has provided the highest resolution observations, 3 pc, barely enough to resolve the largest molecular clouds (MC's) in these galaxies. Thus, to establish the true structure of the molecular clouds it is fundamental to study the molecular gas in the LMC/SMC at considerably higher resolution, i.e., 0.1 pc or even less. We suggest observations of a sample of molecular clouds in the LMC and the SMC, i.e., galaxies of significantly different metallicities. Within each galaxy, regions of different radiative environments should be observed. This strategy has the prospect to separate the impact of the metallicity and the radiation field on the structure of the clouds. With a resolution of 0.2 arcseconds we reach linear scales of 0.05 pc. The Magellanic clouds provide a star formation environment which is different in many aspects from that of the Galaxy. It is likely that some of the aspects of starformation in this low metallicity environment are similar to those in the early universe. The high angular resolution provided by ALMA will allow detection of bipolar outflows from young massive stars embedded in the MCs. 3. Number of sources: 5 clouds in the LMC (2 in 30DOR and 3 in N159); 2 in the SMC. (Four clouds in the LMC and one in the SMC are associated with the formation of massive stars and two, one in each galaxy, are located in more quiscent regions) 4. Coordinates: 4.1. 30 Doradus and N159 in LMC: (RA=05h40m, DEC=-69d) N66 and SMCB1-1 in SMC: (RA=01h, DEC=-73d) Two MC in LMC one in 30DOR (intense radiation field) the other N159 in more quiescent surroundings. Similarly for the SMC, N66 (intense radiation field). SMCB1-1, cold quiescent cloud. 4.2. Moving target: no 4.3. Time critical: no 4.4. Scheduling constraints: (optional) 5. Spatial scales: 5.1. Angular resolution (arcsec): 1" - 0.2" (0.2" for a few pointings) 0.2"= 0.05 pc linear 5.2. Range of spatial scales/FOV (arcsec): At 230 GHz (Band 6) the field-of-view is about 35" 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: (e.g., nutator switch; frequency switch; position switch; on-the-fly mapping; and combinations of the above) 6.2. Stand-alone ACA: beneficial 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: potentially beneficial if significantly better dynamic range is available 6.4. Subarrays of 12m baseline-ALMA antennas: no 7. Frequencies: 7.1. Receiver band: Band 6 7.2. Lines and Frequencies (GHz): 2 frequency settings (220, 230 GHz) 7.3. Spectral resolution (km/s): 0.2 km/s 7.4. Bandwidth or spectral coverage (km/s or GHz): 50 km/s 8. Continuum flux density: 8.1. Typical value (Jy): 0.5 (LMC), 0.1 (SMC) (take average value of set of objects) (optional: provide range of fluxes for set of objects) 8.2. Required continuum rms (Jy or K): 0.05 Jy (LMC), 0.01 Jy (SMC) 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 5% repeatability 5% relative ( 1-3% would be useful ) 9. Line intensity: 9.1. Typical value (K or Jy): 2-10K (LMC), 1K (SMC) for 12CO For 13CO the values are a factor of 10 lower (take average value of set of objects) (optional: provide range of values for set of objects) 9.2. Required rms per channel (K or Jy): 0.5K (LMC), 0.1K (SMC) for 12CO 9.3. Spectral dynamic range: 9.4. Calibration requirements: absolute ( 5% ) repeatability (at least 5%) relative ( 1-3% would be useful ) 10. Polarization: no 11. Integration time for each observing mode/receiver setting (hr): Integration time per setting: 50 hrs survey plus 120 hrs high res mode= 170 hrs *Survey mode - 1", 0.2 km/s resolution at 230 GHz (sensitivity 0.1 K after 40 minutes): CO 2-1 fov 35": 30DOR: 2x16= 32 pointings to cover two MCs in 30 DOR times 40 minutes = 20 hrs N159: 3x16 = 48 pointings to cover three clouds = 30 hrs Double this time to cover similar regions in the SMC = 100 hrs N66: 2x16= 32 pointings to cover two MCs in N66 (HII region plus spur) SMCB1-1 = 1x 16" Survey total: 150 hrs *High res mode - 0.2", 0.1 km/s resolution 230 GHz (sensitivity 0.7 K after 20 hours): 30DOR: two pointings in one cloud: central and outskirt - 20 hours per pointing N159: two pointings in two clouds - N159W and N159S A total of 120 hours In SMC = 120 hours. N66: two pointings in two cloud: - 10 hours per pointing - SMCB1-1: two pointing - central and outskirt - 10 hours per pointing High res total: 240 hrs 12. Total integration time for program (hr): -------------------------------------------------- Review v2.0: 1.8.1 Structure and star formation of LMC/SMC molecular clouds Aalto 390 hours there seems no overlap with 1.8.4 and 1.8.5 the emphasis here is on CO, the other two deal with continuum study to separate impact of metallicity and radiation field. Number of sources is very well justified. They propose a low resolution "survey" mode and a high resolution mode. If I understand this correctly the survey mode is used to study the structure of the ISM.. which is what this proposal is about. The high resolution mode will be used to find bipolar outflows. This seems scientifically less unique . survey mode is total 150 hours 1" resolution, i.e. 0.25pc high resolution mode is 240 hours 0.2" 0.05pc Abstract says 0.1pc resolution is needed to study structure of ISM. I am not sure how hard that number is. High resolution mode could be overkill?