Inside-out galaxy growth?

Figure 1 from Bezanson et al., http://arxiv.org/abs/0903.2044

The authors investigate possible mechanisms for the size and surface
density evolution from z=2.3 to the present. The above figure shows
average stellar density profiles of ellipticals at z=0 (colored
lines, representing different masses) and at high redshift (grey
shaded region). At small radii the profiles match pretty well, but
farther out they diverge rather drastically. This suggests that the
compact high-redshift quiescent galaxies may be the cores of massive
ellipticals in the local universe, growing from the inside out via
minor mergers. (later in the paper the authors show that major
mergers can't produce the observed evolution in the mass-size relation).