Caltech faint galaxy redshift survey. VIII. Analysis of the field J0053+1234

The results of a spectroscopic investigation of a complete sample of object s with K-s < 20 mag in a 2' by 7.'3 held at J005325+1234 are reported. Reds hifts 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 (e xcluding 24 Galactic stars). The redshift identifications are believed to b e almost complete for z < 0.8. Approximately one-half of the galaxies lie i n five narrow redshift features with local velocity dispersions of similar to 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 vi rialization. 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 cl ustered, albeit more weakly, are less luminous and more frequently exhibit strong emission lines. These "isolated" galaxies therefore appear, on avera ge, to form stars at later epochs than the strongly clustered galaxies. The galaxy spectral energy distributions (SEDs) derived from our UBVRIK photom etry are also very closely correlated with the galaxy spectral types and lu minosities. These results have strong implications for the analysis of reds hift surveys at intermediate redshift. The sample is used to investigate th e evolution of the combined galaxy luminosity function back to z = 0.8. No significant change is found in the characteristic luminosity L*, and only w eak color changes are detected, consistent with passive evolution. The blue galaxy-luminosity function is more dwarf rich than the red galaxy-luminosi ty function. No significant change in the comoving density is found in this sample out to z similar to 1.4, assuming that the objects without redshift s (16% of the sample) are galaxies, essentially all of which have z > 0.8. This suggests that mergers are not important among the objects in this samp le. A population of extremely red objects with (R-K) > 5 mag exists in the infrared-selected sample; all four such objects with redshifts are found to be absorption-line galaxies with z similar to 1. Most of the very red obje cts therefore appear to be galaxies with z greater than or similar to 1 tha t are not heavily reddened by dust. A measure of the UV extinction at 2400 Angstrom for the emission-line galaxies of a factor of 2 is obtained, imply ing only modest UV extinction in high-redshift star-forming galaxies.