| Issue |
A&A
Volume 479, Number 2, February IV 2008
|
|
|---|---|---|
| Page(s) | 335 - 346 | |
| Section | Cosmology (including clusters of galaxies) | |
| DOI | https://doi.org/10.1051/0004-6361:20077723 | |
| Published online | 04 December 2007 | |
The galaxy luminosity function of the Abell 496 cluster and its spatial variations*
1
Institut d'Astrophysique de Paris (UMR 7095: CNRS & Université Pierre et Marie Curie), 98bis Bd Arago, 75014 Paris, France e-mail: boue@iap.fr
2
LAM, Traverse du Siphon, 13012 Marseille, France
3
Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France
4
Observatoire de Paris, GEPI (UMR 8111: CNRS & Université Denis Diderot), 61 Av. de l'Observatoire, 75014 Paris, France
5
Observatoire de Paris, section Meudon, LUTH, CNRS-UMR 8102, Université Paris 7, 5 Pl. Janssen, 92195 Meudon, France
Received:
26
April
2007
Accepted:
27
November
2007
Context.The faint end slopes of galaxy luminosity functions (LFs) in clusters
of galaxies have been observed
in some cases
to vary with clustercentric distance
and should be influenced by the physical processes (mergers, tides)
affecting cluster galaxies. However, there is a wide disagreement on the
values of the faint end LF slopes, ranging from -1 to -2.3 in the
magnitude range 
.
Aims.We investigate the LF in the very relaxed cluster Abell 496.
Methods.Our analysis is based on deep images obtained at CFHT with
MegaPrime/MegaCam in four bands (u*g'r'i') covering a
deg2 region, which is centred on the cluster Abell 496
and extends to near its virial radius. The LFs are estimated by
statistically subtracting a reference field taken as the mean of the 4 Deep fields of the CFHTLS survey. Background contamination is
minimised by cutting out galaxies redder than the observed Red
Sequence in the 
versus i' colour-magnitude diagram.
Results.In Abell 496, the global LFs show a faint end slope of
and vary little with observing band.
Without colour cuts, the LFs are much noisier but not significantly
steeper.
The faint end slopes
show a statistically significant steepening from
in the central region (extending to half a virial radius) to
in
the Southern envelope of
the cluster.
Cosmic variance and uncertain star-galaxy separation are our main
limiting factors in measuring the
faint end of the LFs.
The large-scale environment of Abell 496, probed with the fairly
complete 6dFGS catalogue, shows a statistically significant 36 Mpc long
filament at 
.
Conclusions.Our LFs do not display the large number
of dwarf galaxies (
) inferred by
several authors, whose analyses
may suffer from field contamination
caused by non-existent or
inadequate colour cuts.
Alternatively, different clusters may have different faint end slopes,
but this is hard to reconcile with the
wide range of slopes found for given clusters and for wide sets of
clusters.
Key words: galaxies: clusters: individual: Abell 496 / galaxies: luminosity functions, mass function
Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is also partly based on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.
© ESO, 2008
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