Evolution of Cluster and Field Elliptical Galaxies at 0.2 < [ITAL]z[/ITAL] < 0.6 in the CNOC Cluster Survey

Open Access
Publisher Website
Google Scholar
Abstract
Two-dimensional surface photometry has been done for 166 early-type galaxies (bulge/total luminosity B/T > 0.6) in three fields of the Canadian Network for Observational Cosmology (CNOC) cluster survey. These galaxies are either spectroscopically confirmed members of clusters at z = 0.23 (45 galaxies), 0.43 (22), and 0.55 (16) or field galaxies in the same redshift range. An additional 51 early-type galaxies in the rich cluster Abell 2256 at z = 0.06 were analyzed with the same technique. The resulting structural and surface brightness measurements show that, in the plane of absolute magnitude MAB(B) versus log Re (half-light radius), the locus of cluster elliptical galaxies shifts monotonically with redshift so that at redshifts of (0.23, 0.43, 0.55), galaxies of a given size are more luminous by -0.25 ± 0.10, -0.55 ± 0.12, and -0.74 ± 0.21 mag with respect to the same relation measured at z = 0.06 (adopting q0 = 0.5). There is no evidence that early-type galaxies in the field evolve differently from those in clusters, although we emphasize that our cluster sample is dominated by galaxies far from the dense cluster core. If dynamical processes do not substantially modify the size-luminosity relation for early-type galaxies over the observed redshift range, then these galaxies have undergone significant luminosity evolution over the past half of the age of the universe. The amount of brightening is consistent with passive evolution models of old, single-burst stellar populations.
All Related Versions