Deep Surveys with GISMO : Searching for submillimeter galaxies at the highest redshifts

Abstract:
The GISMO 2 mm camera is currently the only bolometer camera operating at the IRAM 30m telescope, which is available to the astronomical community through the semi-annual IRAM call for proposals. GISMO provides a general capability across a wide range of astronomical sources, including observations of galactic dust and free-free emission, the characterization of the SEDs of nearby galaxies, and detecting dusty galaxies at high redshifts. The 2 mm band is in particular well suited to trace the first dusty galaxies in the universe, since their redshifted SEDs peak close to GISMO's observing frequency, whereas the medium redshift galaxy foreground is almost invisible in this band. This effect makes GISMO's deep field observations a valuable complement, rather than a redundancy, to the HERSCHEL far-infrared and sub-mm surveys. There are two ongoing deep sky surveys with GISMO. Following a brief summary of a sample of current projects, I will describe one of those surveys in detail: the GISMO Deep Field (GDF) survey, which is centered on the Hubble Deep Field North. This survey by now has reached the confusion limit (we measure a confusion noise of 60 microJy) and we have extracted  12 + 3 sources in a 7 arcminute wide field, of which roughly half have known submillimeter galaxy counterparts, including the enigmatic submillimeter galaxy SCUBA-850.1. Our detailed statistical analysis of the  GDF data provides a solid estimate of the expected rate of false detections among those source identifications. Furthermore, numerical simulations were used, to estimate the "completeness" of our set of extracted sources. A comparison of our observations with model predictions shows that our results are in good agreement with galaxy count models. Among the sources without counterparts,  for which interferometric follow-up observations are scheduled, simple models predict an appreciable number to be at very high redshifts (z~5-6 and above) with intrinsic luminosities of a few 10^12 L_sol.  However, only follow up observations will tell, whether those models indeed are a fair representation of the evolution of dusty and luminous galaxies at very high redshifts.  Finally, I will give an outlook into the future by outlining the variety of science questions which we anticipate to address in the future with 2 mm deep survey data, followed by a brief introduction to the dual band (1 mm and 2 mm) bolometer camera GISMO-2, which we expect will replace GISMO in 2014.