CANADA-FRANCE REDSHIFT SURVEY - HUBBLE-SPACE-TELESCOPE IMAGING OF HIGH-REDSHIFT FIELD GALAXIES

Hubble Space Telescope B and I images are presented of 32 galaxies wit h secure redshifts in the range 0.5 < z < 1.2 from the Canada-France R edshift Survey, a complete sample of galaxies with 17.5 less than or e qual to I(AB)less than or equal to 22.5. These galaxies exhibit the sa me range of morphological types as seen locally, i.e., ellipticals, sp irals, and irregulars. The galaxies look far less regular in the B ima ges (rest-frame ultraviolet) than at longer wavelengths, underlining t he fact that optical images of galaxies at still higher redshift shoul d be interpreted with caution. Quantitative analyses of the galaxies y ield disk sizes, bulge fractions, and colors for each component. At th ese redshifts, galaxy disks show clear evidence for surface brightness evolution. The mean rest-frame central surface brightness of the disk s of normal late-type galaxies is mu(AB)(B) = 20.2 +/- 0.25 mag arcsec (-2), about 1.2 mag brighter than the Freeman law for nearby galaxies. Some degree of peculiarity/asymmetry is measurable in 10 (30%) of the galaxies, and four (13%) show clear signs of interaction/mergers. The re are nine galaxies (30%) dominated by blue compact components. These components, which appear to be related to star formation, occur most often in peculiar/asymmetric galaxies (some of which appear to be inte racting), but a few are in otherwise normal galaxies. Thus, of the gal axies bluer than present-day Sb, one-third are ''blue nucleated galaxi es'' and half are late-type galaxies with disks which are significantl y brighter than normal galaxies at z = 0. Taken together, these two ef fects must be responsible for much of the observed evolution of the lu minosity function of blue galaxies.