The nature of the dwarf population in Abell 868 |
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| Authors: | Peter J Boyce Steven Phillipps J Bryn Jones Simon P Driver Rodney M Smith Warrick J Couch |
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| Institution: | 1Astrophysics Group, Department of Physics, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL;2Astronomy Group, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD;3School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS;4Department of Physics and Astronomy, University of Wales Cardiff, PO Box 913, Cardiff, CF2 3YB;5School of Physics, University of New South Wales, Sydney, NSW 2052, Australia |
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| Abstract: | We present the results of a study of the morphology of the dwarf galaxy population in Abell 868, a rich, intermediate-redshift  cluster which has a galaxy luminosity function (LF) with a steep faint-end slope  . A statistical background subtraction method is employed to study the  colour distribution of the cluster galaxies. This distribution suggests that the galaxies contributing to the faint-end of the measured cluster LF can be split into three populations: dwarf irregular galaxies (dIrrs) with  dwarf elliptical galaxies (dEs) with  and contaminating background giant ellipticals (gEs) with  . The removal of the contribution of the background gEs from the counts only marginally lessens the faint-end slope  . However, the removal of the contribution of the dIrrs from the counts produces a flat LF  . The dEs and the dIrrs have similar spatial distributions within the cluster, except that the dIrrs appear to be totally absent within a central projected radius of about 0.2 Mpc  . The number densities of both dEs and dIrrs appear to fall off beyond a projected radius of ≃ 0.35 Mpc. We suggest that the dE and dIrr populations of A868 have been associated with the cluster for similar time-scales, but evolutionary processes such as 'galaxy harassment' tend to fade the dIrr galaxies while having a much smaller effect on the dE galaxies. The harassment would be expected to have the greatest effect on dwarfs residing in the central parts of the cluster. |
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| Keywords: | methods: data analysis galaxies: clusters: general galaxies: clusters: individual: Abell 868 galaxies: dwarf galaxies: evolution galaxies: luminosity function mass function |
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