The evolution of the brightest cluster galaxies since z~1 from the ESO Distant Cluster Survey EDisCS - AstrophysicsReport as inadecuate

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Abstract: Abridged We present K-band data for the brightest cluster galaxies BCGsfrom the ESO Distant Cluster Survey. These data are combined with photometryfrom Aragon-Salamanca et al. 1998 and a low-redshift comparison sample fromvon der Linden et al. 2007. The K-band Hubble diagram for BCGs exhibits verylow scatter ~0.35mag since z=1. The colour and $K$-band luminosity evolutionof the BCGs are in good agreement with passively-evolving stellar populationsformed at z>2. We do not detect any significant change in the stellar mass ofthe BCG since z~1. These results do not seem to depend on the velocitydispersion of the parent cluster. There is a correlation between the 1Dvelocity dispersion of the clusters and the K-band luminosity of the BCGsafter correcting for passive evolution. The clusters with large velocitydispersions tend to have brighter BCGs, i.e., BCGs with larger stellar masses.This dependency, although significant, is relatively weak: the stellar mass ofthe BCGs changes only by ~70% over a two-order-of-magnitude range in clustermass. This dependency doesn-t change significantly with redshift. The models ofDe Lucia and Blaizot 2007 predict colours which are in reasonable agreementwith the observations because the growth in stellar mass is dominated by theaccretion of old stars. However, the stellar mass in the model BCGs grows by afactor of 3-4 since z=1, a growth rate which seems to be ruled out by theobservations. The models predict a dependency between the BCG-s stellar massand the velocity dispersion of the parent cluster in the same sense as thedata, but the dependency is significantly stronger than observed. However, onemajor difficulty in this comparison is that we have measured fixed metricaperture magnitudes while the models compute total luminosities.

Author: I.M. Whiley 1, A. Aragon-Salamanca 1 G. De Lucia 2 A. von der Linden 2, S.P. Bamford 3, P. Best 4, M.N. Bremer 5, P. Jablonka 6,


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