Mass assembly and morphological transformations since z? 3 from CANDELS

We quantify the evolution of the stellar mass functions (SMFs) of star-forming and quiescent galaxies as a function of morphology from z ? 3 to the present. Our sample consists of ?50 000 galaxies in the CANDELS fields (?880 arcmin2), which we divide into four main morphological types, i.e. pure bulge-dominated systems, pure spiral disc-dominated, intermediate two-component bulge+disc systems and irregular disturbed galaxies. At z ? 2, 80 per cent of the stellarmass density of star-forming galaxies is in irregular systems. However, by z ? 0.5, irregular objects only dominate at stellar masses below 109M_. A majority of the star-forming irregulars present at z ? 2 undergo a gradual transformation from disturbed to normal spiral disc morphologies by z ? 1 without significant interruption to their star formation. Rejuvenation after a quenching event does not seem to be common except perhaps for the most massive objects, because the fraction of bulge-dominated star-forming galaxies with M?/M_ > 1010.7 reaches 40 per cent at z < 1. Quenching implies the presence of a bulge: the abundance of massive red discs is negligible at all redshifts over 2 dex in stellar mass. However, the dominant quenching mechanism evolves. At z > 2, the SMF of quiescent galaxies aboveM ? is dominated by compact spheroids. Quenching at this early epoch destroys the disc and produces a compact remnant unless the star-forming progenitors at even higher redshifts are significantly more dense. At 1 < z