Huertas-Company, M., Bernardi, M., Perez-Gonzalez, P.G., Ashby, M.L.N., Barro, G., Conselice, C., Daddi, E., Dekel, A., Dimauro, P., Faber, S.M., Grogin, N.A., Kartaltepe, J.S., Kocevski, D.D., Koekemoer, A.M., Koo, D.C., Mei, S. and Shankar, F. (2016) Mass assembly and morphological transformations since z~3 from CANDELS. Monthly Notices of the Royal Astronomical Society, 462 (4), 4495-4516. (doi:10.1093/mnras/stw1866).
Abstract
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 ~ 50000 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. Our main results are:
1) Star-formation: At z ~ 2, 80% of the stellar mass density of star-forming galaxies is in irregular systems. However, by z ~ 0.5, irregular objects only dominate at stellar masses below 109 Msun. 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*/Msun > 1010.7 reaches 40% at z < 1.
2) Quenching: We confirm that galaxies reaching a stellar mass of M* ~ 1010.8 Msun (M*) tend to quench. Also, 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 above M* 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 < 2, the majority of newly quenched galaxies are discs with a significant central bulge. This suggests that mass quenching at this epoch starts from the inner parts and preserves the disc. At z < 1, the high-mass end of the passive SMF is globally in place and the evolution mostly happens at stellar masses below 1010 Msun. These low-mass galaxies are compact, bulge-dominated systems, which were environmentally quenched: destruction of the disc through ram-pressure stripping is the likely process.
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