The Evolution of Cluster Early-Type Galaxies over the Past 8 Gyr (0910.4007v1)

Abstract: We present the Fundamental Plane (FP) of early-type galaxies in the clusters of galaxies RXJ1415.1+3612 at z=1.013. This is the first detailed FP investigation of cluster early-type galaxies at redshift z=1. The distant cluster galaxies follow a steeper FP relation compared to the local FP. The change in the slope of the FP can be interpreted as a mass-dependent evolution. To analyse in more detail the galaxy population in high redshift galaxy clusters at 0.8<z\<1, we combine our sample with a previous detailed spectroscopic study of 38 early-type galaxies in two distant galaxy clusters, RXJ0152.7-1357 at z=0.83 and RXJ1226.9+3332 at z=0.89. For all clusters Gemini/GMOS spectroscopy with high signal-to-noise and intermediate-resolution has been acquired to measure the internal kinematics and stellar populations of the galaxies. From HST/ACS imaging, surface brightness profiles, morphologies and structural parameters were derived for the galaxy sample. The least massive galaxies (M=2x10^{10}M_{\sun}) in our sample have experienced their most recent major star formation burst at z_{form}~1.1. For massive galaxies (M\>2x10^{11}M_{\sun}) the bulk of their stellar populations have been formed earlier z_{form}>~1.6. Our results confirm previous findings by Jorgensen et al. This suggests that the less massive galaxies in the distant clusters have much younger stellar populations than their more massive counterparts. One explanation is that low-mass cluster galaxies have experienced more extended star formation histories with more frequent bursts of star formation with shorter duration compared to the formation history of high-mass cluster galaxies.