Spectroscopic survey of 1.4 GHz and 24 μm sources in the Spitzer First Look Survey with WIYN Hydra

We present an optical spectroscopic survey of 24 mu m and 1.4 GHz sources, detected in the Spitzer extragalactic First Look Survey ( FLS), using the multifiber spectrograph, Hydra, on the WIYN telescope. We have obtained spectra for 772 sources, with flux densities above 0.15 mJy in the infrared and 0.09mJy in the radio. The redshifts measured in this survey are mostly in the range 0 < z < 0.4, with a distribution peaking at z similar to 0.2. Detailed spectral analysis of our sources reveals that the majority are emission-line star-forming galaxies, with star formation rates in the range 0.2Y 200 M-circle dot yr(-1). The rates estimated from the H alpha line fluxes are found to be on average consistent with those derived from the 1.4 GHz luminosities. For these star-forming systems, we find that the 24 mu m and 1.4 GHz flux densities follow an infrared-radio correlation, which can be characterized by a value of q(24) = 0.83, with a 1 sigma scatter of 0.31. Our WIYN Hydra database of spectra nicely complements those obtained by the Sloan Digital Sky Survey in the region at lower redshift, as well as the MMT Hectospec survey by Papovich et al. in 2006, and brings the redshift completeness to 70% for sources brighter than 2 mJy at 24 mu m. Applying the classical 1/V-max method, we derive new 24 mu m and 1.4 GHz luminosity functions, using all known redshifts in the FLS. We find evidence for evolution in both the 1.4 GHz and 24 mu m luminosity functions in the redshift range 0 < z < 1. The redshift catalog and spectra presented in this paper are available at the Spitzer FLS Web site.