Hubble Space Telescope B and I images are presented of 32 galaxies with secure redshifts in the range 0.5 < z < 1.2 from the Canada-France Redshift Survey, a complete sample of galaxies with 17.5 <= IAB <= 22.5. These galaxies exhibit the same range of morphological types as seen locally, i.e., ellipticals, spirals, and irregulars. The galaxies look far less regular in the B images (rest-frame ultraviolet) than at longer wavelengths, underlining the fact that optical images of galaxies at still higher redshift should be interpreted with caution. Quantitative analyses of the galaxies yield disk sizes, bulge fractions, and colors for each component. At these redshifts, galaxy disks show clear evidence for surface brightness evolution. The mean rest-frame central surface brightness of the disks 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. There 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 interacting), but a few are in otherwise normal galaxies. Thus, of the galaxies bluer than present-day Sb, one-third are "blue nucleated galaxies" and half are late-type galaxies with disks which are significantly brighter than normal galaxies at z = 0. Taken together, these two effects must be responsible for much of the observed evolution of the luminosity function of blue galaxies.
The Astrophysical Journal
- Pub Date:
- September 1995
- GALAXIES: EVOLUTION;
- GALAXIES: FUNDAMENTAL PARAMETERS;
- uuencoded compressed postscript, 8 pages, 1 table + 5 figures in a separate part. Also available at http://www.astro.utoronto.ca/~lilly/CFRS/ . Accepted for publication in ApJ Letters