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On the galaxy luminosity function in the central regions of the Coma cluster

Abstract

We have obtained new redshifts for 265 objects in the central 48~×\times~25~arcmin2^2 region of the Coma cluster. When supplemented with literature data, our redshift sample is 95~\% complete up to a magnitude b26.5_{26.5}=18.0 (the magnitudes are taken from the photometric sample of Godwin et al. 1983). Using redshift-confirmed membership for 205 galaxies, and the location in the colour-magnitude diagram for another 91 galaxies, we have built a sample of cluster members which is complete up to b26.5_{26.5}=20.0. We show that the Coma cluster luminosity function cannot be adequately fitted by a single Schechter (1976) function, because of a dip in the magnitude distribution at b26.5_{26.5}\sim17. The superposition of an Erlang (or a Gauss) and a Schechter function provides a significantly better fit. We compare the luminosity function of Coma to those of other clusters, and of the field. Luminosity functions for rich clusters look similar, with a maximum at Mb19.5+5×logh50M_{b} \simeq -19.5 + 5 \times \log h_{50}, while the Virgo and the field luminosity functions show a nearly monotonic behaviour. These differences may be produced by physical processes related to the environment which affect the luminosities of a certain class of cluster galaxies.Comment: 7 pages, uuencoded postscript file (figures included) Accepted for publication on A&

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    Last time updated on 12/11/2016