Evidence of major dry mergers at M* > 2 x 10^11 Msun from curvature in
  early-type galaxy scaling relations?
  For early-type galaxies, the correlations between stellar mass and size,
velocity dispersion, surface brightness, color, axis ratio and color-gradient
all indicate that two mass scales, M* = 3 x 10^10 Msun and M* = 2 x 10^11 Msun,
are special. The smaller scale could mark the transition between wet and dry
mergers, or it could be related to the interplay between SN and AGN feedback,
although quantitative measures of this transition may be affected by
morphological contamination. At the more massive scale, mean axis ratios and
color gradients are maximal, and above it, the colors are redder, the sizes
larger and the velocity dispersions smaller than expected based on the scaling
at lower M*. In contrast, the color-sigma relation, and indeed, most scaling
relations with sigma, are not curved: they are well-described by a single power
law, or in some cases, are almost completely flat. When major dry mergers
change masses, sizes, axis ratios and color gradients, they are expected to
change the colors or velocity dispersions much less. Therefore, the fact that
scaling relations at sigma > 150 km/s show no features, whereas the size-M*,
b/a-M*, color-M* and color gradient-M* relations do, suggests that M* = 2 x
10^11 Msun is the scale above which major dry mergers dominate the assembly
histories of early-type galaxies.
