Redshift z similar to 1 field galaxies observed with the Keck Telescope and the Hubble Space Telescope

We report results based on 35 new spectroscopic redshifts obtained with the Reck Telescope for field galaxies that also have photometry and morphology from survey images taken by the refurbished Hubble Space Telescope. A sample of 24 redshifts for galaxies fainter than I = 22 has a median redshift of z similar to 0.81. This result is inconsistent with the lower median redshift of z similar to 0.6 predicted by the ''maximal merger models'' of Carlberg, which otherwise fit existing data. The data match an extrapolation of the Canada France Redshift Survey (CFRS), as well as predictions of certain mild luminosity-evolution models. Nearly half of the redshifts lie in two structures at z similar or equal to 0.81 and z similar or equal to 1.0, showing the presence of high-density concentrations spanning scales of similar to 1 h(-1) Mpc, i.e., the size of groups. We find emission lines or the presence of possible neighbors in seven of nine otherwise luminous galaxies with red central regions at redshifts beyond z similar to 0.7. We also note a diversity of morphological types among blue galaxies at z similar to 1, including small compact galaxies, ''chains,'' and ''blue nucleated galaxies.'' These morphologies are found among local, but generally less luminous, galaxies. Distant blue galaxies also include apparently normal late-type spirals. These findings could imply modest bursts of star formation caused by mergers or interactions of small, gas-rich galaxies with each other or with larger, well-formed galaxies. This first glimpse of very faint z similar to 1 field galaxies of diverse colors and morphologies suggests that a mixture of physical processes is at work in the formation and evolution of faint held galaxies.