First insights into the Spitzer Wide-area Infrared Extragalactic Legacy Survey (SWIRE) galaxy populations

We characterize the Spitzer Wide-area Infrared Extragalactic Legacy Survey (SWIRE) galaxy populations in the SWIRE validation field within the Lockman Hole, based on the 3.6 - 24 mum Spitzer data and deep U, g', r', i' optical imaging within an area similar to 1/3 deg(2) for similar to 16,000 Spitzer SWIRE sources. The entire SWIRE survey will discover over 2.3 million galaxies at 3.6 mum and almost 350,000 at 24 mum; similar to 70,000 of these will be five-band 3.6-24 mum detections. The colors cover a broad range, generally well represented by redshifted spectral energy distributions of known galaxy populations; however, significant samples of unusually blue objects in the [3.6] - [4.5] color are found, as well as many objects very red in the 3.6 - 24 mum mid-IR. Nine of these are investigated and are interpreted as star-forming systems, starbursts, and active galactic nuclei (AGNs) from z = 0.37 to 2.8, with luminosities from L-IR = 10(10.3) to 10(13.7) L-..