The Phoenix Deep Survey: Spectroscopic Catalog

The Phoenix Deep Survey is a multiwavelength survey based on deep 1.4 GHz radio imaging, reaching well into the sub-100 μJy level. One of the aims of this survey is to characterize the submillijansky radio population, exploring its nature and evolution. In this paper we present the catalog and results of the spectroscopic observations aimed at characterizing the optically "bright" (R ≲ 21.5 mag) counterparts of faint radio sources. Of 371 sources with redshift determination, 21% have absorption lines only, 11% show active galactic nucleus signatures, 32% are star-forming galaxies, 34% show narrow emission lines that do not allow detailed spectral classification (owing to poor signal-to-noise ratio and/or lack of diagnostic emission lines), and the remaining 2% are identified with stars. For the star-forming galaxies with a Balmer decrement measurement we find a median extinction of A_Hα = 1.9 mag, higher than that of optically selected samples. This is a result of the radio selection, which is not biased against dusty systems. Using the available spectroscopic information, we estimate the radio luminosity function of star-forming galaxies in two independent redshift bins at z ≈ 0.1 and 0.3, respectively. We find direct evidence for strong luminosity evolution of these systems consistent with L_{1.4 GHz} ∝ (1 + z)^2.7.