Evolution of the near-infrared in rich galaxy clusters

Abstract

We present the K-band (2.2 μm) luminosity functions (LFs) of the X-ray-luminous clusters MS1054-0321 (z=0.823), MS0451-0305 (z=0.55), Abell 963 (z=0.206), Abell 665 (z=0.182) and Abell 1795 (z=0.063) down to absolute magnitudes M_K=-20. Our measurements probe fainter absolute magnitudes than do any previous studies of the near-infrared LFs of clusters. All the clusters are found to have similar LFs within the errors, when the galaxy populations are evolved to redshift z=0. It is known that the most massive bound systems in the Universe at all redshifts are X-ray-luminous clusters. Therefore, assuming that the clusters in our sample correspond to a single population seen at different redshifts, the results here imply that not only had the stars in present-day ellipticals in rich clusters formed by z=0.8, but that they existed in as luminous galaxies then as they do today. Additionally, the clusters have K-band LFs which appear to be consistent with the K-band field LF in the range -24<M_K<-22, although the uncertainties in both the field and cluster samples are large.