A search for faint low surface brightness galaxies in the relaxed cluster Abell 496^⋆

¹ LAM, Pôle de l’Étoile Site de Château-Gombert, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
² Department of Physics and Astronomy, Northwestern University, 2131 Sheridan Road, Evanston IL 60208-2900, USA
³ UPMC Université Paris 06, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
e-mail: durret@iap.fr
⁴ CNRS, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France

Received: 16 July 2010
Accepted: 15 January 2011

Abstract

Context. Cluster faint low surface brightness galaxies (fLSBs) are difficult to observe. Consequently, their origin, physical properties and number density are not well known. After a first search for fLSBs in the highly substructured Coma cluster, we present here a search for fLSBs in the nearly relaxed Abell 496 cluster.

Aims. Abell 496 appears to be a much more relaxed cluster than Coma, but still embedded in a large scale filament of galaxies. Our aim is to compare the properties of fLSBs in these two very different clusters, to search for environmental effects.

Methods. Based on deep CFHT/Megacam images in the u^∗, g′, r′ and i′ bands, we selected galaxies with r′ > 21 and μ_r′ > 24 mag arcsec^-2. We estimated photometric redshifts for all these galaxies and kept the 142 fLSBs with photo-z < 0.2.

Results. In a g′ − i′ versus i′ color–magnitude diagram, we find that a large part of these fLSBs follow the red sequence (RS) of brighter galaxies. The fLSBs within  ± 1σ of the RS show a homogeneous spatial distribution, while those above the RS appear to be concentrated along the large scale filament of galaxies.

Conclusions. These properties are interpreted as agreeing with the idea that RS fLSBs are formed in groups prior to cluster assembly. The formation of red fLSBs could be related to infalling galaxies.