The evolution of the field and cluster morphology-density relation for mass-selected samples of galaxies

The Sloan Digital Sky Survey (SDSS) and photometric/ spectroscopic surveys in the GOODS- South field (the Chandra Deep Field-South, CDF- S) are used to construct volume- limited, stellar- mass- selected samples of galaxies at redshifts 0 < z < 1. The CDF- S sample at 0.6 < z < 1.0 contains 207 galaxies complete down to M = 4 x 10(10) M-circle dot (for a diet'' Salpeter initial mass function), corresponding to a luminosity limit for red galaxies of M-B = -20.1. The SDSS sample at 0: 020 < z < 0: 045 contains 2003 galaxies down to the same mass limit, which corresponds to MB = -19: 3 for red galaxies. Morphologies are determined with an automated method, using the Sersic parameter n and a measure of the residual from the model fits, called bumpiness,'' to distinguish different morphologies. These classifications are verified with visual classifications. In agreement with previous studies, 65%-70% of the galaxies are located on the red sequence, both at z similar to 0.03 and at z similar to 0.8. Similarly, 65%-70% of the galaxies have n > 2.5. The fraction of E +/- S0 galaxies is 43% +/- 3% at z similar to 0: 03 and 48% +/- 7% at z similar to 0.8; i. e., it has not changed significantly since z similar to 0: 8. When combined with recent results for cluster galaxies in the same redshift range, we find that the morphology- density relation for galaxies more massive than 0.5M* has remained constant since at least z similar to 0.8. This implies that galaxies evolve in mass, morphology, and density such that the morphology- density relation does not change. In particular, the decline of star formation activity and the accompanying increase in the stellar mass density of red galaxies since z similar to 1 must happen without large changes in the early- type galaxy fraction in a given environment.