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The traditional use of fixed apertures in determining the well known color-magnitude (CM) relation of early type galaxies, coupled with the presence of radial color gradients within these systems, introduces a bias in the CM relation itself. The effect of this bias is studied here deriving a CM relation which is based on color measurements carried out homogeneously within an aperture of radius equal to that of the galaxy effective radius. A sample of 48 giant early-type galaxies in the Coma cluster, with CCD observations in the U- and V-band, is used for this derivation. It is found that internal radial color gradients in early-type galaxies cannot be neglected when discussing the colors of these systems, and that the CM relation derived using color measurements within the effective radius is significantly flatter than those based on fixed-aperture color measurements. With the presently available data it is impossible to determine whether the relation is completely flat, or whether a small correlation is still present between galaxy color and luminosity.
In this letter we present a study of the color magnitude relation of 468 early-type galaxies in the Virgo Cluster with Sloan Digital Sky Survey imaging data. The analysis of our homogeneous, model-independent data set reveals that, in all colors (u-g
We present the analysis of the color-magnitude relation (CMR) for a sample of 57 X-ray detected Abell clusters within the redshift interval 0.02 <= z <= 0.18. We use the B-R vs R color-magnitude plane to establish that the CMR is present in all our l
We present the ultraviolet (UV) color-color relation of early-type galaxies (ETGs) in the nearby universe (0.05 < z < 0.12) to investigate the properties of hot stellar populations responsible for the UV excess (UVX). The initial sample of ETGs is se
We performed B and R band surface photometry for E/S0 galaxies in a nearby rich cluster ABELL 2199 to investigate their B-R color gradients (d(B-R)/dlogr). Our aims are to study statistical properties of the color gradients and, by comparing them wit
We present a study of the color evolution of elliptical and S0 galaxies in six clusters of galaxies inside the redshift range 0.78 < z < 1.27. For each cluster, we used imaging from the Hubble Space Telescope to determine morphological types by both