EDP Sciences
Free access
Volume 408, Number 1, September II 2003
Page(s) 57 - 65
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20030971

A&A 408, 57-65 (2003)
DOI: 10.1051/0004-6361:20030971

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

A. Mercurio1, M. Massarotti2, P. Merluzzi2, M. Girardi1, F. La Barbera2 and G. Busarello2

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

(Received 27 February 2003 / Accepted 19 June 2003)

We derive the luminosity functions in three bands (BVR) for the rich galaxy cluster ABCG 209 at  z=0.21. The data cover an area of ~78 arcmin 2 in the B and  R bands, while a mosaic of three pointings was obtained in the V band, covering an area of approximately 160 arcmin 2. The galaxy sample is complete to  B = 22.8 ( $N {\rm _{gal}} = 339$), V = 22.5 ( $N{\rm _{gal}} = 1078$) and  R = 22.0 ( $N {\rm _{gal}} = 679$). 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 V = 20.5-21.5 and R = 20.0-21.0. 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.

Key words: galaxies: clusters: individual: Abell 209 -- galaxies: photometry -- galaxies: luminosity function, mass function

Offprint request: A. Mercurio, mercurio@ts.astro.it

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