Curvature in the color-magnitude relation but not in color-sigma: Major
  dry mergers at M* > 2 x 10^11 Msun?
  The color-magnitude relation of early-type galaxies differs slightly but
significantly from a pure power-law, curving downwards at low and upwards at
large luminosities (Mr>-20.5 and Mr<-22.5). This remains true of the color-size
relation, and is even more apparent with stellar mass (M* < 3x10^10 Msun and M*
> 2x10^11 Msun). The upwards curvature at the massive end does not appear to be
due to stellar population effects. In contrast, the color-sigma relation is
well-described by a single power law. Since major dry mergers change neither
the colors nor sigma, but they do change masses and sizes, the clear features
observed in the scaling relations with M*, but not with sigma > 150 km/s,
suggest that M* > 2x10^11 Msun is the scale above which major dry mergers
dominate the assembly history. We discuss three models of the merger histories
since z ~ 1 which are compatible with our measurements. In all three models,
dry mergers are responsible for the flattening of the color-M* relation at M* >
3x10^10 Msun - wet mergers only matter at smaller masses. At M* > 2 x 10^11
Msun, the merger histories in one model are dominated by major rather than
minor dry mergers, as suggested by the axis ratio and color gradient trends. In
another, although both major and minor mergers occur at the high mass end, the
minor mergers contribute primarily to the formation of the ICL, rather than to
the mass growth of the central massive galaxy. A final model assumes that the
reddest objects were assembled by a mix of major and minor dry mergers.
