On the nature of faint low surface brightness galaxies in the Coma cluster^*

¹ LAM, Pôle de l'Etoile Site de Château-Gombert, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France e-mail: christophe.adami@oamp.fr
² Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 Av. Edouard Belin, 31400 Toulouse, France
³ Department of Physics and Astronomy, Northwestern University, 2131 Sheridan Road, Evanston IL 60208-2900, USA
⁴ Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743, USA
⁵ Institut d'Astrophysique de Paris, CNRS, UMR 7095, Université Pierre et Marie Curie, 98bis Bd Arago, 75014 Paris, France

Received: 27 March 2008
Accepted: 26 November 2008

Abstract

Context. This project is the continuation of our study of faint Low Surface Brightness Galaxies (fLSBs) in one of the densest nearby () galaxy regions known, the Coma cluster.

Aims. Our goal is to improve our understanding of the nature of these objects by comparing the broad band spectral energy distribution with population synthesis models, in order to infer ages, dust extinction and spectral characteristics.

Methods. The data were obtained with the MEGACAM and CFH12K cameras at the CFHT. We used the resulting photometry in 5 broad band filters (u*, B, V, R, and I) that included new u*-band data to fit spectral models. With these spectral fits we inferred a cluster membership criterium, as well as the ages, dust extinctions, and photometric types of these fLSBs.

Results. We show that about half of the Coma cluster fLSBs have a spectral energy distribution well represented in our template library (best fit fLSBs, BF) while the other half present a flux deficit at ultraviolet wavelengths (moderately good fit fLSBs, MGF). Among the BF fLSBs, ~80% are probably part of the Coma cluster based on their spectral energy distribution. BF fLSBs are relatively young (younger than 2.3 Gyr for 90% of the sample) non-starburst objects. The later their type, the younger the fLSBs are. A significant part of the BF fLSBs are quite dusty objects (1/3 have A_V greater than 1.5). BF fLSBs are low stellar mass objects (the later their type the less massive they are), with stellar masses comparable to globular clusters for the faintest ones. Their characteristics are partly correlated with infall directions, confirming the disruptive origin for at least part of them.