BLAST Large-scale Extragalactic Submillimeter Survey Results

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a suborbital surveying experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the Milky Way) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between three arrays, observes simultaneously in broadband (30%) spectral windows at 250, 350, and 500µm, akin to the SPIRE instrument on Herschel. The optical design is based on a 2m diameter telescope, providing nearly diffraction-limited resolution of 36“ at 250µm. BLAST performed a test flight in 2003 and has since made two scientifically productive long-duration balloon flights: a 100 hour flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in 2005 June; and a 250 hour, circumpolar flight from McMurdo Station, Antarctica in 2006 December. A deep, confusion limited, 0.8 deg² map nested in a wide, 8.6 deg² map in the direction of GOODS-South was made during the 2006 flight. Approximately half of all the light from stars is absorbed and reprocessed by dust. The resulting emission is grey body with a temperature near 30K. While it is believed that this radiation makes up the Far Infrared Background (FIRB) detected by COBE, it had not been resolved into individual galaxies. Combining BLAST data with data from Spitzer in the same region, we determine that at 500µm all of the FIRB comes from sources that are identified in deep 24µm surveys and that 70% of the FIRB comes from sources with z>1.2. Furthermore, we determine the number of galaxies as a function of flux and frequency in the submillimeter revealing a distinct evolution in the galaxy population from low to high redshift. The BLAST collaboration acknowledges the support of NASA, NSF Office of Polar Programs, the CSA (Canada), the STFC (UK), and NSERC (Canada)