FIELD GALAXY EVOLUTION SINCE Z-APPROXIMATE-TO-1 FROM A SAMPLE OF QSO ABSORPTION-SELECTED GALAXIES

We present some of the results of a large survey aimed at establishing the properties of galaxies selected by their having produced detectab le Mg II lambda lambda 2796, 2803 absorption in the spectra of backgro und QSOs. The present sample covers the redshift range 0.2 less than o r equal to z less than or equal to 1.0, with (z) = 0.65. From an exten sive program of optical and near-IR imaging and optical spectroscopy, we find that the galaxies appear to be similar to normal galaxies at t he present epoch, ranging from late-type spiral galaxies to those whos e spectra and colors resemble present-day ellipticals. Contrary to som e faint field galaxy samples selected using different criteria, over t he redshift range observed we find no evidence for significant evoluti on in rest frame B-K color, space density, or (rest frame B or K) lumi nosity. The ''average'' Mg II absorbing galaxy appears to be consisten t with a normal 0.7 L(B) Sb galaxy having a roughly constant star for mation rate since z similar to 1, although galaxies spanning a range o f a factor of similar to 70 in luminosity are found in the absorber sa mple. The diffuse gas cross section imposed by studies of this kind ap pears to be biased against the relatively underluminous, blue galaxies which apparently dominate the number counts at faint magnitudes. Howe ver, essentially all ''normal'' field galaxies, independent of spectro scopic type, appear to be potential QSO absorbers.