Journal Article

On the accuracy of the high-redshift cluster luminosity function

R. P. Muñoz, N. D. Padilla and L. F. Barrientos

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 392, issue 2, pages 655-664
Published in print January 2009 | ISSN: 0035-8711
Published online December 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.14059.x
On the accuracy of the high-redshift cluster luminosity function

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We study the reliability of the statistical background subtraction method for computing the Ks-band luminosity function of cluster galaxies at z∼ 1 using mock Red-sequence Cluster Survey cluster catalogues constructed from galform semi-analytic galaxies. The underlying cluster luminosity function in the mocks is compatible with recent estimates at z∼ 1 by several authors. We simulate different samples where the number of clusters with Ks-band photometry goes from five to a maximum of 50, in order to find the most suitable observational sample to carry out this study; the current observational status in the near-infrared wavelength range has been reached using five real clusters at z∼ 1. We compute the composite luminosity function for several samples of galaxy clusters with masses ≃1.5 × 1014 M assuming a flux-limited, complete sample of galaxies down to Ks= 21.0 mag. We find that the Schechter fit parameters Ks* and α for a sample of galaxies with no redshift information are rather poorly constrained if both parameters are allowed to vary freely; if α is fixed at a fiducial value, then Ks* shows significantly improved stochastic uncertainties but can be influenced by systematic deviations. We find a significantly improved accuracy in the luminosity function parameters when adding photometric redshift information for bright cluster galaxies. The impact of a 10-fold increase in the number of clusters with available Ks-band photometry is that of decreasing stochastic errors in Ks* and α by factors of ≃2 and ≃4, respectively, for accuracies of up to (ΔKs*/Ks*)stochastic= 0.02 and (Δα/α)stochastic= 0.09. The dwarf-to-giant ratios inferred from the luminosity functions of red-sequence galaxies in the mock catalogue agree very well with the underlying values; however, there is an indication that the semi-analytic model overpredicts the abundance of dwarf galaxies by up to a factor of 3 with respect to recent measurements. Finally, we find that in order to use estimates of Ks* to study the formation redshift of cluster galaxies at z= 1, the sample would need to contain 520 z∼ 1 clusters, for an accuracy of ∼2 Gyr at the 68 per cent confidence level. However, combining this method with other estimates may significantly reduce the sample size, and allow important new constraints on galaxy formation models.

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

Journal Article.  7081 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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