The evolution of the red sequence slope in massive galaxy clusters
  We investigate the evolution of the optical and near-infrared
colour-magnitude relation in an homogeneous sample of massive clusters from z =
1 to the present epoch. By comparing deep Hubble Space Telescope ACS imaging of
X-ray selected MACS survey clusters at z = 0.5 to the similarly selected LARCS
sample at z = 0.1 we find that the rest-frame d(U -V)/dV slope of the
colour-magnitude relation evolves with redshift which we attribute to the build
up of the red sequence over time. This rest frame slope evolution is not
adequately reproduced by that predicted from semi-analytic models based on the
Millennium Simulation despite a prescription for the build up of the red
sequence by in-falling galaxies, 'strangulation'. We observe no strong
correlation between this slope and the cluster environment at a given redshift
demonstrating that the observed evolution is not due to a secondary
correlation. Also presented are near-infrared UKIRT WFCAM observations of the
LARCS clusters which confirm and improve on the the result from Stott et al.
(2007) finding that there has been a two-fold increase in faint MV > -20
galaxies on the red sequence since z = 0.5 to a significance of 5sigma.
