Faint Galaxy Redshift Survey VIII : Analysis for the Field J 0053 + 1234

The results of a spectroscopic investigation of a complete sample of objects with Ks < 20 mag in a 2 by 7.3 arcmin field at J005325+1234 are reported. Redshifts were successfully obtained for 163 of the 195 objects in the sample; these redshifts lie in the range [0.173, 1.44] and have a median of 0.58 (excluding 24 Galactic stars). The redshift identifications are believed to be almost complete for z < 0.8. Approximately half of the galaxies lie in five narrow redshift features with local velocity dispersions of ∼300 km s−1. These narrow redshift “peaks” are primarily populated both by absorption–line galaxies and the most luminous galaxies in the sample, although the incidence of emission lines in the luminous galaxies increases with redshift. The estimated dynamical masses of these redshift peaks, and the sky distribution of the galaxies within them, appear similar to groups or poor clusters of galaxies in the local universe at various stages of virialization. Some groups of galaxies therefore form at epochs z > 1.5, and the galaxies in such groups appear to be coeval and to show little sign of ongoing star formation. The galaxies outside the redshift peaks are also clustered, albeit more weakly, are less luminous and more frequently exhibit strong emission lines. These “isolated” galaxies therefore appear, on average, to form stars at later epochs than the strongly clustered galaxies. The galaxy SEDs derived from our UBV RIK photometry are also very closely correlated with the galaxy spectral types and luminosities. These results have strong implications for the analysis of redshift surveys at intermediate redshift. The sample is used to investigate the evolution of the combined galaxy luminosity function back to z = 0.8. No significant change is found in the characteristic luminosity Based in large part on observations obtained at the W.M. Keck Observatory, which is operated jointly by the California Institute of Technology and the University of California Palomar Observatory, Mail Stop 105-24, California Institute of Technology, Pasadena, CA 91125 Theoretical Astrophysics, California Institute of Technology, Mail Stop 130-33, Pasadena, CA 91125 Current Address: Institute for Advanced Study, Olden Lane, Princeton, NJ 08540 Hubble Fellow Current Address: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Mail Stop 20, Cambridge, MA 02138