Optical luminosity functions of the Abell galaxy cluster ABCG 209 at z = 0.21^*

¹ Dipartimento di Astronomia, Università degli Studi di Trieste, via Tiepolo 11, 34100 Trieste, Italy e-mail: mercurio@ts.astro.it; girardi@ts.astro.it
² INAF – Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy

Corresponding author: A. Mercurio, mercurio@ts.astro.it

Received: 27 February 2003
Accepted: 19 June 2003

Abstract

We derive the luminosity functions in three bands (BVR) for the rich galaxy cluster ABCG 209 at . The data cover an area of ~78 arcmin² in the B and R bands, while a mosaic of three pointings was obtained in the V band, covering an area of approximately 160 arcmin². The galaxy sample is complete to  (), () and  (). Although the fit of a single Schechter function cannot be rejected in any band, the luminosity functions are better described by a sum of two Schechter functions for bright and faint galaxies, respectively. There is an indication for a presence of a dip in the luminosity functions in the range and . We find a marked luminosity segregation, in the sense that the number ratio of bright–to–faint galaxies decreases by a factor 4 from the center to outer regions. Our analysis supports the idea that ABCG 209 is an evolved cluster, resulting from the merger of two or more sub–clusters.