The Phoenix Deep Survey: Spectroscopic Catalog

The Phoenix Deep Survey is a multi-wavelength survey based on deep 1.4 GHzradio imaging, reaching well into the sub-100 microJy level. One of the aims ofthis survey is to characterize the sub-mJy radio population, exploring itsnature and evolution. In this paper we present the catalog and results of thespectroscopic observations aimed at characterizing the optically ``bright''(R<~ 21.5 mag) counterparts of faint radio sources. Out of 371 sources withredshift determination, 21% have absorption lines only, 11% show AGNsignatures, 32% are star-forming galaxies, 34% show narrow emission lines thatdo not allow detailed spectral classification (due to poor signal-to-noiseratio and/or lack of diagnostic emission lines) and the remaining 2% areidentified with stars. For the star-forming galaxies with a Balmer decrementmeasurement we find a median extinction of A(Ha)=1.9 mag, higher than that ofoptically selected samples. This is a result of the radio selection, which isnot biased against dusty systems. Using the available spectroscopicinformation, we estimate the radio luminosity function of star-forming galaxiesin two independent redshift bins at z~0.1 and 0.3 respectively. We find directevidence for strong luminosity evolution of these systems consistent with L(1.4GHz) ~ (1+z)^(2.7).