The near-infrared luminosity function of cluster galaxies beyond redshift one

Abstract

Aims. We determined the K s band luminosity function (LF), and inferred the corresponding stellar mass function, of cluster galaxies at redshift z 1.2, using near-infrared images of three X-ray luminous clusters at z = 1.11, 1.24, 1.27. Methods. The composite LF was derived down to M * + 4, by means of statistical background subtraction, and is well described by a Schechter function with K * s = 20.5 +0.4−1 and α = −1.0 +0.2 −0.3 . Using available X-ray mass profiles we determined the M/L ratios of these three clusters, which tend to be lower than those measured in the local universe. Finally, from the K s band composite LF we derived the stellar mass function of cluster galaxies. Results. With these data, no significant difference can be seen between the cluster galaxies LF and the LF of field galaxies at similar redshift. We also found no significant evolution out to z 1.2 in the bright (<M * + 4) part of the LF probed in this study, apart from a brightening of 1.3 mag of the characteristic magnitude of the high redshift LF. We confirm, and extend to higher redshift, the result from previous work that the redshift evolution of the characteristic magnitude M * is consistent with passive evolution of a stellar population formed at z > 2. Conclusions. The results obtained in this work support and extend previous findings that most of the stars in bright galaxies were formed at high redshift, and that K s -bright (M > 10 11 M ) galaxies were already in place at z 1.2, at least in the central regions of X-ray luminous clusters. Together with recent results on the field galaxy stellar mass function, this implies that most of the stellar mass is already assembled in massive galaxies by z 1, both in low and high density environments.

The abundance and colours of galaxies in high-redshift clusters in the cold dark matter cosmology

“…The limits on the excess counts are determined based upon the upper and lower limits on the number of sources with a spectroscopic redshift or a photometric redshift within 3σ of the cluster redshift. Strazzullo et al (2006) argue that the background contamination from lensed galaxies magnified by the cluster itself is small. They conclude that their estimate for the CGLF is consistent with previous determinations at similar or lower redshifts.…”

“…(ii) Strazzullo et al (2006): Strazzullo et al, present K s -band imaging for the clusters RDCS J0910+5422 (K s < 21.5) and RDCS J1252.9−2927 (K s < 24.5), as well as H 160 (F160W) imaging for RX J0848+4453 (H 160 < 25). They present an estimate for the CGLF for each cluster, as well as a composite estimate for all three of the clusters.…”

“…In Figs 2-4 we show observational estimates for the CGLF from Strazzullo et al (2006Strazzullo et al ( , 2010 and Fassbender et al (2014), as well as our estimates based upon the data sets of Mei et al (2006b), Hilton et al (2009) andSnyder et al (2012). Strazzullo et al (2006Strazzullo et al ( , 2010 estimate the CGLF for their galaxy cluster sample by using a reference field, down to an equivalent photometric depth or deeper, to statistically remove the contribution from background galaxies, which is known to bias CGLF estimates (Andreon, Punzi & Grado 2005), particularly at bright magnitudes where the statistics are typically quite poor.…”

“…Strazzullo et al (2006Strazzullo et al ( , 2010 estimate the CGLF for their galaxy cluster sample by using a reference field, down to an equivalent photometric depth or deeper, to statistically remove the contribution from background galaxies, which is known to bias CGLF estimates (Andreon, Punzi & Grado 2005), particularly at bright magnitudes where the statistics are typically quite poor. The CGLF is estimated by subtracting the counts in the reference field (normalized to the solid angle of the cluster) from the counts in the cluster field.…”

“…The CGLF is estimated by subtracting the counts in the reference field (normalized to the solid angle of the cluster) from the counts in the cluster field. The uncertainties on the CGLFs estimated by Strazzullo et al (2006Strazzullo et al ( , 2010 are Poisson, with both clusters and possible background field interlopers summed in quadrature. The limits on the excess counts are determined based upon the upper and lower limits on the number of sources with a spectroscopic redshift or a photometric redshift within 3σ of the cluster redshift.…”