Apr 24, 2014
Johannes Staguhn, The Johns Hopkins University
"Deep Surveys with GISMO : Searching for submillimeter galaxies at the highest redshifts "
The GISMO 2 mm camera at the IRAM 30m telescope 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. 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.
Targeted GISMO observations of even more extreme high redshift galaxies have been obtained during our most recent observing run. I will present preliminary results from these observations, which have the potential to put strong constraints on the formation of dark matter halos and the production of metals in the early universe.
Finally, I will give an outlook into the future by outlining the variety of science questions we anticipate to address with the dual band (1 mm and 2 mm) bolometer camera GISMO-2, which we expect will replace GISMO at the IRAM 30 m telescope in the second half of 2014.