Title Gas and Dust in 30 Doradus Pi J. Turner Time 80 hrs 1.8.5. Gas and Dust in 30 Doradus J. Turner 2. 30 Doradus is the most luminous nebula in the Large Magellanic Clouds and comparable to the most luminous HII regions in the Milky Way (NGC 3603, Carina). The star cluster within 30 Doradus is a "populous" cluster, or small super star cluster, which may be similar to a small globular cluster in nature. There are younger, embedded surrounding this luminous region, which may have been triggered by 30 Doradus. There are 60 or 70 O3 and O4 stars exciting 30 Dor, which is 200 pc in diameter. Large luminous regions such as 30 Dor are rare. 30 Doradus is only 50 kpc away, and the continuum sensitivity of ALMA allows us to map its free-free emission, dust continuum, and CO line emission at high resolution and sensitivity. We propose to map the nebula in the CO lines and continuum in Bands 3, 6, and 7 to trace the ionized gas, molecular gas, and dust within the core of 30 Doradus. We will be able to map down to EM~10^6, similar to Orion, to gas column densities of roughly a few x 10^20 (caveats below) and to clump masses of about 40 Msun in dust emission. Three bands are needed to separate free-free and dust continuum contributions. The primary driver for the time request is the continuum. There is abundant HI line emission in the 30 Dor region, but the dominant large molecular streamer is located a degree or so to the south, and extends over 3 degrees in length. This proposal will map small knots of emission associated with or directly affected by the 30 Doradus nebula. CO knots have been detected at lower resolution. 3. Number of sources: 1 4. Coordinates: 4. 1 field, 20'x20' in size, in LMC 5:39, -69 4.2 Moving target: no 4.3 Time critical: no 5. Spatial scales: 5.1 Angular resolution: 1" 5.2 Range of spatial scales/FOV: 20'x20' field: OTF 5.3 Single dish: yes 5.4 ACA: yes 5.5 Subarrays: no 6. Frequencies: 6.1 Receiver band: Bands 3, 6, 7 6.2 Continuum 8 GHz 6.3 Spectral resolution 3 km/s 6.4 Spectral coverage 300 km/s (LMC is not a big galaxy) 7. Continuum flux density 7.1 Typical value: 0. to 2 mJy/beam 7.2 Continuum peak value: 50 mJy/beam 7.3 Required continuum rms: 0.12, 0.42, 0.44 mJy/beam for Bands 3,6,7 (0.01K) 7.4 Dynamic range in image: 1000:1 8. Line Intensity 8.1. Typical value (K or Jy): 0.1-1 K 8.2. Required rms per channel (K or Jy): 0.2 (345 GHz)-1 (115)K (see note above) 8.3. Spectral dynamic range: 25 9. Polarization N/A 10. Integration time per observing mode/receiver setting (hr): (2700 seconds/15' square OTF map) x 11 maps = 8 hrs Band 3 (5400 seconds/15' square OTF map) x 16 maps = 24 hrs Band 6 (5400 seconds/15' square OTF map) x 32 maps = 48 hrs Band 7 11. Total integration time for program: 80 hours 12. Comments on observing strategy These will be OTF maps, 15' x 15' to cover the 200 pc diameter core of 30 Doradus. I assumed a scan rate of 30"/second for the OTF map, so each row takes 30 seconds. To get the amount of time per map, I took a sampling rate (row spacing) of 10" for Band 3, and 5" for Bands 6 and 7 for simplicity. These could be tweaked, but they sample over the Nyquist rate, which is probably desirable. The ultimate goal is to achieve about 0.01K in each band in continuum. Resolution is 1" = 0.24 pc. Line resolution 3 km/s. Matched beam observations required, 1" beams. Zero spacing desirable to allow spatial smoothing for sensitivity to lower level emission. Sensitivities. 3mm 8 hours gives about 11 maps, x 1.6 seconds/sample/map = 17 seconds per sample. This gives continuum sensitivities of .13 mJy and .012 K. Good enough to see a 320 Msun clump in dust emission (the mass is gas mass) at 3mm, and free-free emission from EM ~ 10^6 cm-6 pc at 5 sigma (Orionish). Line: 1.02 K times 3 km/s =3 K km/s, which would be N_H2 = 6 x 10^20 for a Galactic conversion factor, although the LMC is underluminous, at least in CO(1-0). Compact HII knots easily detectable. 870um: 48 hrs gives 32 OTF maps, at 0.375 sec/sample/map = 12 seconds/sample. Continuum sensitivities are 0.436mJy, .0044K. Can see compact HII regions here but not Orions. Can detect a clump of 40 Msun in dust emission at 4 sigma, scaling from observed Orion clumps, which corresponds to a gas density of about 10^5 in a 0.24 pc (1") diameter region. Line sensitivity of .22K x 3km/s would be .7 K km/s, or 1.4 x 10^20 for a Galactic conversion factor and CO(3-2)/CO(1-0) ~1. However, J=2-1 lines are often brighter than 1-0 in LMC. Could compensate to some degree for high Xco. 1.3mm: In between the two above, use this to separate gas and dust. Extremely optically thick HII regions can still be rising into the millimeter. **************************************************************** Review Chris Wilson: program looks O.K. but did not check integration times -------------------------------------------------- Review v2.0: 1.8.5 Gas and dust in 30 Doradus Turner 80 hours this looks very ok to me. There is overlap with 1.8.4, but there proposed sensitivity is much better. Those proposals could easily be combined.