First Insights into the SWIRE Galaxy Populations

Abstract

We characterize the SWIRE galaxy populations in the SWIRE validation field within the Lockman Hole, based on the 3.6-24$\hat{I}¼$ Spitzer data and deep U,g',r',r' optical imaging within an area ~1/3 sq. deg for ~16,000 Spitzer-SWIRE sources. The entire SWIRE survey will discover over 2.3 million galaxies at 3.6$\hat{I}¼$m and almost 350,000 at 24$\hat{I}¼$m; ~70,000 of these will be 5-band 3.6-24$\hat{I}¼$ 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]$\hat{I}¼$m color are found, as well as many objects very red in the 3.6-24$\hat{I}¼$m mid-IR. Nine of these are investigated and are interpreted as star-forming systems, starbursts and AGN from z=0.37 to 2.8, with luminosities from L${}_{IR}$=10${}^{10.3}$ to 10${}^{13.7}$ L${}_{\odot }$

Accepted for publication in the ApJ Supplements Spitzer Special Issue 17 pages, 4 figures