The Bimodal Color-Magnitude Distribution of Galaxies from the SDSS

Abstract

We analyze the distribution in color versus absolute magnitude of a low-redshift sample of galaxies from the Sloan Digital Sky Survey [4]. For each magnitude bin, the color function can be approximated as the sum of two normal Gaussians, a bimodal function. Thus, the distribution can be deconvolved into two dominant components that have associated color-magnitude relations, dispersion-magnitude relations and luminosity functions. This differs from the classical approach of using cuts in morphology or color to define classes and instead allows for a natural overlap. The observed distribution and the deconvolved red and blue distributions are shown in Fig. 1. We describe some of the results and points to note about the figure, below. For full details, see [1].

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