Spitzer 70 and 160-micron Observations of the Extragalactic First Look Survey

Abstract

We present Spitzer 70um and 160um observations of the Spitzer extragalactic First Look Survey (xFLS). The data reduction techniques and the methods for producing co-added mosaics and source catalogs are discussed. Currently, 26% of the 70um sample and 49% of the 160um-selected sources have redshifts. The majority of sources with redshifts are star-forming galaxies at z<0.5, while about 5% have infrared colors consistent with AGN. The observed infrared colors agree with the spectral energy distribution (SEDs) of local galaxies previously determined from IRAS and ISO data. The average 160um/70um color temperature for the dust is Td~= 30+/-5 K, and the average 70um/24um spectral index is alpha~= 2.4+/-0.4. The observed infrared to radio correlation varies with redshift as expected out to z~1 based on the SEDs of local galaxies. The xFLS number counts at 70um and 160um are consistent within uncertainties with the models of galaxy evolution, but there are indications that the current models may require slight modifications. Deeper 70um observations are needed to constrain the models, and redshifts for the faint sources are required to measure the evolution of the infrared luminosity function.