Spitzer 70 and 160 mu m observations of the extragalactic First Look Survey

We present 70 and 160 mu m observations from 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 70 mu m sample and 49% of the 160 mu m-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 active galactic nuclei. The observed infrared colors agree with the spectral energy distributions (SEDs) of local galaxies previously determined from IRAS and Infrared Space Observatory data. The average 160 mu m/70 mu m color temperature for the dust is T-d similar or equal to 30 +/- 5 K, and the average 70 mu m/24 mu m spectral index is alpha similar or equal to 2.4 +/- 0.4. The observed infrared-to-radio correlation varies with redshift as expected out to z similar to 1 based on the SEDs of local galaxies. The xFLS number counts at 70 and 160 mu m are consistent within uncertainties with the models of galaxy evolution, but there are indications that the current models may require slight modifications. Deeper 70 mu m observations are needed to constrain the models, and redshifts for the faint sources are required to measure the evolution of the infrared luminosity function.