Title Follow-up observations of Spitzer selected galaxies Pi A. Blain Time 560 1. Name of program and authors Follow-up observations of Spitzer selected galaxies Andrew Blain 2. One short paragraph with science goal(s) The Spitzer Space Telescope has provided an effective first look into a representative volume of luminous galaxies with far-infrared emission in the Universe at redshift z~1, typically lower than those of submm-selected galaxies. However, Spitzer provides a short-wavelength (most sensitive out to 23 microns) and unresolved view of the apparent disk galaxies that dominate the luminosity function at this redshifts. Optical redshifts and morphologies are available for many examples, but this combination of information does not provide insight into where the dust-enshrouded star formation is concentrated, and thus into the astrophysical processes - tides, collisions, gravitational collapse -- that are responsible, ALMA provides a unique facility to rapidly image the stryuctures within these galaxies that are required too understand their emission. About 60 square degrees has been surveyed to useful depth using Spitzer, more than half accessible from the South. Spitzer colors, oprical-Spitzer colors and some redshifts are available, and can be used to select a subsample of Spitzer-selected galaxis that span the full range of properties of the galaxy sample, which is likely to involve the formation of the majority of disk stars in the Universe today. There are something like 100000 cataloged galaxies in the final Spitzer fields. Only ALMA can pinpoint the most active regions of these galaxies, and provide information about the mechanisms triggering their luminosity. 3. Number of sources (e.g., 1 deep field of 4'x4', 50 YSO's, 300 T Tauri stars with disks, ...; do NOT list individual sources or your "pet object", except in special cases like LMC, Cen A, HDFS) Of order up to 50000 galaxies, spread over the sky. In equatorial COSMOS field, GOODS-S, HDF-S and Southerly SWIRE fields. This large number can be used to construct an extremely accurate luminosity function, revealing the internal structure of star formation and AGN emission in galaxies spanning the range of luminosities from typical galaxies to the most extreme systems. However, some useful statistical information is available from a sample size as small as a few 1000 targets, allowing a 10-bin luminosity function to be compiled as a function of several Spitzer color classes. 4. Coordinates: 4.1. Rough RA and DEC (e.g., 30 sources in Taurus, 30 in Oph, 20 in Cha, 30 in Lupus) Indicate if there is significant clustering in a particular RA/DEC range (e.g., if objects in one particular RA range take 90% of the time) Should be approximately uniform around the year. 4.2. Moving target: yes/no (e.g. comet, planet, ...) No 4.3. Time critical: yes/no (e.g. SN, GRB, ...) No 4.4. Scheduling constraints: (optional) Good weather required. 5. Spatial scales: 5.1. Angular resolution (arcsec): 0.01"-1" 5.2. Range of spatial scales/FOV (arcsec): (optional: indicate whether single-field, small mosaic, wide-field mosaic...) Single field in general, targeted at known object. 5.3. Required pointing accuracy: (arcsec) 1" 6. Observational setup 6.1. Single dish total power data: no/beneficial/required No 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: no/beneficial/required No, unless standing idle for a bit more collecting area. 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no/beneficial/required Yes, if ACA used 6.4. Subarrays of 12m baseline-ALMA antennas: yes/no No 7. Frequencies: 7.1. Receiver band: Band 3, 4, 5, 6, 7, 8, or 9 In principle all bands to provide excellent SED, but 3,6 and 9 should provide good continuum SED, with the best chance of detecting a CO line coming in band 3 & 4 where fractional bandwidth is greatest, and sensitive to CO(2-1) for 1 404s each 12. Total integration time for program (hr): 5000 sources (estimated, most likely with redshifts) => 560 hours total 13. Comments on observing strategy : (optional) (e.g. line surveys, Target of Opportunity, Sun, ...): -------------------------------------------------- Review v2.0: 1.1.10 Clearly, SED determination of SST selected galaxies using ALMA is an important science case. Time estimations for 90, 230, and 670 GHz bands seem OK. At 350 GHz band, about 16 sec integration per pointing will be sufficient to achieve the required rms sensitivity of 0.5 mJy, so 180 sec each. This results in the total integration time for 5000 sources of 250 hrs. Relaxing of 670 GHz sensitivity requirement will also reduce the total integration time significantly; about 45 sec will achieve the rms sensitivity of 1.5 mJy (still S/N of ~100, seems to be enough). The total time will be then (60+4+16+45)*5000 = 174 hrs, for example. Is it essential to observe both 230 and 350 GHz in terms of SED measurements? More observing bands are better for SED, of course, but it may be possible to reduce the number of observing bands. For instance, about 6 sec integration at around 280 GHz will also achieve a sensitivity of 0.5 mJy rms, and these 3 bands, i.e., 90, 280, and 670 GHz bands observations will be made just (60+6+100)*5000 = 231 hrs or so. (just 20 hrs saving, though)