Photometric and Morphological Properties of Nearby Cluster Galaxies

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Abstract
Photometric observations are presented for 8747 galaxies in the fields of 28 clusters with redshifts in the range 0.05 < z < 0.11 and spanning a wide range in Abell richness class. The primary motivation for this study is to provide a nearby sample of clusters whose galaxy populations can be used to provide an anchor point for evolutionary studies of cluster galaxy populations. The present analysis focuses on the sequence of luminous red galaxies that form a tight correlation in the color-magnitude plane. An ensemble cluster constructed from the full sample shows the red sequence clearly and the observed dispersion—not corrected for observational errors—is σ(V - I) = 0.071 ± 0.006 down to MI(AB) = -19.5. Selecting only early-type galaxies on the basis of their fractional bulge luminosity (B/T) reduces the observed dispersion to σ(V - I) = 0.050 ± 0.006 mag, a significantly smaller dispersion than the full sample at more than the 95% confidence level. The slope of the color-magnitude relation in (V - I)/I is -0.023 ± 0.006. This set of clusters shows a red sequence that has the same mean color in all clusters (V - I)AB = 0.91 ± 0.03 (measured at MI(AB) = -23) and has the same intrinsic dispersion, δ(V - I) = 0.04 ± 0.01, in all clusters within the observational errors. Thus, these clusters form a remarkably homogeneous family as represented by their luminous red galaxy populations.

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