Journal Article

Luminosity functions of XMM–LSS C1 galaxy clusters

Abdulmonem Alshino, Habib Khosroshahi, Trevor Ponman, Jon Willis, Marguerite Pierre, Florian Pacaud and Graham P. Smith

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 401, issue 2, pages 941-962
Published in print January 2010 | ISSN: 0035-8711
Published online January 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15734.x
Luminosity functions of XMM–LSS C1 galaxy clusters

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Canada–France–Hawaii Telescope Legacy Survey optical photometry has been used to study the galaxy luminosity functions (LFs) of 14 X-ray selected clusters from the XMM Large Scale Survey (XMM–LSS) survey. These are mostly groups and poor clusters, with masses (M500) in the range 0.6 to 19 × 1013 M and redshifts 0.05 ≤z≤ 0.61. Hence, these are some of the highest redshift X-ray selected groups to have been studied. Lower and upper colour cuts were used to determine cluster members. We derive individual LFs for all clusters as well as redshift-stacked and temperature-stacked LFs in three filters, g′, r′ and z′, down to M=−14.5. All LFs were fitted by Schechter functions which constrained the faint-end slope, α, but did not always fit well to the bright end. Derived values of α ranged from −1.03 to as steep as −2.1. We find no evidence for upturns at faint magnitudes. Evolution in α was apparent in all bands: it becomes shallower with increasing redshift; for example, in the z′ band it flattened from −1.75 at low redshift to −1.22 in the redshift range z= 0.43–0.61. Eight of our systems lie at z∼ 0.3, and we combine these to generate a galaxy LF in three colours for X-ray selected groups and poor clusters at redshift 0.3. We find that at z∼ 0.3 α is steeper (−1.67) in the green (g′) band than it is (−1.30) in the red (z′) band. This colour trend disappears at low redshift, which we attribute to reddening of faint blue galaxies from z∼ 0.3 to 0. We also calculated the total optical luminosity and found it to correlate strongly with X-ray luminosity (LXL2.1OPT), and also with ICM temperature (LOPTT1.62), consistent with expectations for self-similar clusters with constant mass-to-light ratio. We did not find any convincing correlation of Schechter parameters with mean cluster temperature.

Keywords: galaxies: clusters: general; galaxies: evolution; galaxies: luminosity function, mass function; galaxies: structure

Journal Article.  12207 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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