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

Abstract

We present an optical spectroscopic survey of 24 {μ}m and 1.4GHz 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 above0.15 mJy in the infrared and 0.09 mJy in the radio. The redshiftsmeasured in this survey are mostly in the range 0{\lt}z{\lt}0.4,with a distribution peaking at z~0.2. Detailed spectral analysisof our sources reveals that the majority are emission-line star-forminggalaxies, with star formation rates in the range 0.2-200 M_{solar}yr^{-1}. The rates estimated from the H{α} line fluxes arefound to be on average consistent with those derived from the 1.4GHz luminosities. For these star-forming systems, we find that the24 {μ}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{σ} scatter of 0.31. Our WIYN Hydra database of spectra nicelycomplements those obtained by the Sloan Digital Sky Survey in theregion at lower redshift, as well as the MMT Hectospec survey byPapovich et al. in 2006, and brings the redshift completeness to70% for sources brighter than 2 mJy at 24 {μ}m. Applying theclassical 1/V_{max} method, we derive new 24 {μ}m and 1.4 GHzluminosity functions, using all known redshifts in the FLS. We findevidence for evolution in both the 1.4 GHz and 24 {μ}m luminosityfunctions in the redshift range 0{\lt}z{\lt}1. The redshift catalogand spectra presented in this paper are available at the SpitzerFLS Web site.Based on observations obtained at the WIYN telescope at the Kitt PeakNational Observatory, National Optical Astronomy Observatory, whichis operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation.