First Insights into the SWIRE Galaxy Populations

TL;DR

This study provides initial insights into SWIRE galaxy populations using Spitzer and optical data, revealing diverse galaxy types, including starbursts and AGN, across a broad redshift range.

Contribution

It offers the first detailed characterization of SWIRE galaxy populations in a specific field, highlighting the diversity and properties of galaxies detected by Spitzer.

Findings

Identification of a broad range of galaxy colors and types.

Detection of unusually blue and very red mid-IR objects.

Interpretation of some objects as star-forming systems, starbursts, and AGN.

Abstract

We characterize the SWIRE galaxy populations in the SWIRE validation field within the Lockman Hole, based on the 3.6-24$\mu$ 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$\mu$m and almost 350,000 at 24$\mu$m; ~70,000 of these will be 5-band 3.6-24$\mu$ 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]$\mu$m color are found, as well as many objects very red in the 3.6-24$\mu$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$_{\odot}$