Half-mass radii of quiescent and star-forming galaxies evolve slowly
  from 0 < z < 2.5: implications for galaxy assembly histories
  We use high-resolution, multi-band imaging of ~16,500 galaxies in the CANDELS
fields at 0 < z < 2.5 to study the evolution of color gradients and half-mass
radii over cosmic time. We find that galaxy color gradients at fixed mass
evolve rapidly between z~2.5 and z~1, but remain roughly constant below z~1.
This result implies that the sizes of both star-forming and quiescent galaxies
increase much more slowly than previous studies found using half-light radii.
The half-mass radius evolution of quiescent galaxies is fully consistent with a
model which uses observed minor merger rates to predict the increase in sizes
due to the accretion of small galaxies. Progenitor bias may still contribute to
the growth of quiescent galaxies, particularly if we assume a slower timescale
for the minor merger growth model. The slower half-mass radius evolution of
star-forming galaxies is in tension with cosmological simulations and
semi-analytic galaxy models. Further detailed, consistent comparisons with
simulations are required to place these results in context.
