Evolution of blue E/S0 galaxies from z~1: merger remnants or disk
  rebuilding galaxies?
  Studying outliers from the bimodal distribution of galaxies in the color-mass
space, such as morphological early-type galaxies residing in the blue cloud,
can help to better understand the physical mechanisms that lead galaxy
migrations in this space. In this paper we study the evolution of the
properties of 210 M*/Msol>10^10 blue E/S0s between z~1.4 and z~0.2 in the
COSMOS field with confirmed spectroscopic redshifts from the zCOSMOS 10k
release. We first observe that the threshold mass, defined at z=0 in previous
studies as the mass below which the population of blue early-type galaxies
starts to be abundant relative to passive E/S0s, evolves from log(M*/Msol)~10.1
at z~0.3 to log(M*/Msol)~10.9 at z~1. Second, there seems to be a turn-over
mass in the nature of blue E/S0 galaxies. Above log(M*/Msol)~10.8 blue E/S0
resemble to merger remnants probably migrating to the red-sequence in a
time-scale of ~3 Gyr. Below this mass, they seem to be closer to normal
late-type galaxies as if they were the result of minor mergers which triggered
the central star-formation and built a central bulge component or were
(re)building a disk from the surrounding gas, suggesting that they are moving
back or staying in the blue-cloud. This turn-over mass does not seem to evolve
significantly from z~1 in contrast with the threshold mass and therefore does
not seem to be linked with the relative abundance of blue E/S0s.
