Evolution of the 1.4 GHz radio luminosity function

The results of an optical and infrared investigation of a complete sub-sampleof the Leiden-Berkeley Deep Survey (flux > 1 mJy at 1.4 GHz) are presented.Optical counterparts have been identified for 69 of the 73 sources in the twoHercules fields, and redshifts obtained for 49 of them. Photometric redshiftsare computed from the g,r,i,K data for the remaining 21 sources. This completesample is compared with the radio luminosity functions (RLFs) of Dunlop andPeacock (1990). The RLF models successfully trace the evolution of the radiosources with redshift, but there is some disagreement between theluminosity-dependence of the models and the data. The observed RLF for thelower luminosity population (log P < 26) shows evidence for a cut-off at lowerredshifts (z=0.5-1.5) than for the more powerful objects.Comment: To appear in "After the Dark Ages: When Galaxies Were Young (the Universe at 2 < z < 5)", University of Maryland, October 1998, S. S. Holt and E. P. Smith (eds), (AIP), 4 pages, 4 figures, uses aipproc.sty and epsfig.st