| Abstract | New B VR photometry is listed for the brightest several members of clusters of galaxies, for all HMS groups, and for E galaxies that are identified with radio sources. Measurements are given for a set of 72 stars that define the S20 (FW 130) V - R system used here. The galaxy colors, corrected for K reddening, correlate with galactic latitude and provide a new solution for galactic reddening. A model for galactic absorption similar to that proposed by McClure and Crawford is supported. The reddening variation with galactic latitude is smaller by a factor of 2 than traditional values. Redshifts of E galaxies in the range 0 < z < 0.9 can be uniquely determined by a combination of four broad-band colors alone near effective wavelengths of B, V, R, and A> = 8500 A. The color-redshift relations are tight, and agree with predicted distributions obtained by redshifting a standard spectrum through the measuring bands. The data admit color evolution for E and SO galaxies at rates that must be smaller than (B - V)! log t 0.3 mag color change between ages of 10 and 1010 years, i.e., 0.3 mag dex `This observational limit agrees with the color-decay rates that are expected to lie between 0.3 and 0.1 mag dex -1 from empirical considerations of C-M diagrams. Although small, such rates are large enough to encourage an observational search for color evolution in E galaxies where the look-back time is significantly long (z > 0.4). Color distributions are calculated for various models for the production of galaxies as a function of time. Comparison with the observed distribution shows that (1) there are no young (t < 10 years) E galaxies in our sample, and (2) the formation epoch for E galaxies was peaked toward the old age side of the distribution. The data are consistent with the view that E galaxies formed at some definite time in the past. Continuous E galaxy formation, as required in the steady-state model, is not verified here. The data do not contradict the hypothesis that giant E galaxies are the same age as the elliptical galaxy component of the Local Group (t 1010 years). Subject headings: cosmology - galaxies, photometry of - interstellar reddening - redshifis |
