Galaxy evolution in the environment of ABCG 209

¹ Osservatorio Astronomico di Capodimonte, v. Moiariello 16, 80131 Napoli, Italy e-mail: chris@na.astro.it
² Departimemto di Astronomia, Università degli Studi di Trieste, v. Tiepolo 11, 34100 Trieste, Italy

Received: 10 December 2003
Accepted: 19 May 2004

Abstract

We examine the environmental effects on the photometric properties of galaxies for the rich galaxy cluster ABCG 209 at . We use archive CFHT optical imaging of a field centred on the cluster to produce a galaxy sample complete to  and . Both the composite and red sequence galaxy luminosity functions are found to be dependent on the local galaxy surface density, their faint-end slopes becoming shallower with increasing density. We explain this as a combination of the morphology-density relation, and dwarf galaxies being cannibalised and/or disrupted by the cD galaxy and the ICM in the cluster core. The  colour of the red sequence itself appears 0.02 mag redder for the highest-density regions, indicative of their stellar populations being marginally (<5%) older or (<20%) more metal-rich. This may be due to the galaxies themselves forming earliest in the rarest overdensities marked by rich clusters, or their star-formation being suppressed earliest by the ICM.