Red Sequence Slope Evolution

from Stott et al., http://arxiv.org/abs/0901.1227

This paper investigates the evolution of the color-magnitude relation
slope in massive galaxy clusters using two samples: LARCS at z~0.1
and MACS at z~0.5. The observed slope evolution is compared to
predictions from the Bower et al. (2006) semianalytic model (taking
into account AGN feedback and "strangulation). The above figure
shows the rest-frame slope evolution, including the data themselves
(points), a fit to the data (solid line), and the Bower et al.
prediction (dashed line). The discrepancy between the models and
observations is attributed to either the shutdown of star formation
in clusters being stronger than the models predict, or possibly
differential chemical evolution (e.g. faint galaxies have
preferentially higher chemical enrichment rates). Oddly, the
observed-frame red sequence slope matches the models very well;
apparently this is because the observed evolution is dominated by the
K-correction.