Galaxy Stellar Mass Assembly between 0.2<z<2 from the S-COSMOS survey
  We follow the galaxy stellar mass assembly by morphological and spectral type
in the COSMOS 2-deg^2 field. We derive the stellar mass functions and stellar
mass densities from z=2 to z=0.2 using 196,000 galaxies selected at F(3.6
micron) > 1 microJy with accurate photometric redshifts
(sigma_((zp-zs)/(1+zs))=0.008 at i<22.5). Using a spectral classification, we
find that z~1 is an epoch of transition in the stellar mass assembly of
quiescent galaxies. Their stellar mass density increases by 1.1 dex between
z=1.5-2 and z=0.8-1 (Delta t ~2.5 Gyr), but only by 0.3 dex between z=0.8-1 and
z~0.1 (Delta t ~ 6 Gyr). Then, we add the morphological information and find
that 80-90% of the massive quiescent galaxies (log(M)~11) have an elliptical
morphology at z<0.8. Therefore, a dominant mechanism links the shutdown of star
formation and the acquisition of an elliptical morphology in massive galaxies.
Still, a significant fraction of quiescent galaxies present a Spi/Irr
morphology at low mass (40-60% at log(M)~9.5), but this fraction is smaller
than predicted by semi-analytical models using a ``halo quenching'' recipe. We
also analyze the evolution of star-forming galaxies and split them into
``intermediate activity'' and ``high activity'' galaxies. We find that the most
massive ``high activity'' galaxies end their high star formation rate phase
first. Finally, the space density of massive star-forming galaxies becomes
lower than the space density of massive elliptical galaxies at z<1. As a
consequence, the rate of ``wet mergers'' involved in the formation of the most
massive ellipticals must decline very rapidly at z<1, which could explain the
observed slow down in the assembly of these quiescent and massive sources.
