zCOSMOS - 10k-bright spectroscopic sample. The bimodality in the Galaxy Stellar Mass Function: exploring its evolution with redshift
Abstract
We present the Galaxy Stellar Mass Function (MF) up to z~1 from the zCOSMOS-bright 10k spectroscopic sample. We investigate the total MF and the contribution of ETGs and LTGs, defined by different criteria (SED, morphology or star formation). We unveil a galaxy bimodality in the global MF, better represented by 2 Schechter functions dominated by ETGs and LTGs, respectively. For the global population we confirm that low-mass galaxies number density increases later and faster than for massive galaxies. We find that the MF evolution at intermediate-low values of Mstar (logM<10.6) is mostly explained by the growth in stellar mass driven by smoothly decreasing star formation activities. The low residual evolution is consistent with ~0.16 merger per galaxy per Gyr (of which fewer than 0.1 are major). We find that ETGs increase in number density with cosmic time faster for decreasing Mstar, with a median "building redshift" increasing with mass, in contrast with hierarchical models. For LTGs we find that the number density of blue or spiral galaxies remains almost constant from z~1. Instead, the most extreme population of active star forming galaxies is rapidly decreasing in number density. We suggest a transformation from blue active spirals of intermediate mass into blue quiescent and successively (1-2 Gyr after) into red passive types. The complete morphological transformation into red spheroidals, required longer time-scales or follows after 1-2 Gyr. A continuous replacement of blue galaxies is expected by low-mass active spirals growing in stellar mass. We estimate that on average ~25% of blue galaxies is transforming into red per Gyr for logM<11. We conclude that the build-up of galaxies and ETGs follows the same downsizing trend with mass as the formation of their stars, converse to the trend predicted by current SAMs. We expect a negligible evolution of the global Galaxy Baryonic MF.
Cite
@article{arxiv.0907.5416,
title = {zCOSMOS - 10k-bright spectroscopic sample. The bimodality in the Galaxy Stellar Mass Function: exploring its evolution with redshift},
author = {L. Pozzetti and M. Bolzonella and E. Zucca and G. Zamorani and S. Lilly and A. Renzini and M. Moresco and M. Mignoli and P. Cassata and L. Tasca and F. Lamareille and C. Maier and B. Meneux and C. Halliday and P. Oesch and D. Vergani and K. Caputi and K. Kovac and A. Cimatti and O. Cucciati and A. Iovino and Y. Peng and M. Carollo and T. Contini and J. P. Kneib and O. Le F'evre and V. Mainieri and M. Scodeggio and S. Bardelli and A. Bongiorno and G. Coppa and S. de la Torre and L. de Ravel and P. Franzetti and B. Garilli and P. Kampczyk and C. Knobel and J. F. Le Borgne and V. Le Brun and R. Pell`o and E. Perez Montero and E. Ricciardelli and J. D. Silverman and M. Tanaka and L. Tresse and U. Abbas and D. Bottini and A. Cappi and L. Guzzo and A. M. Koekemoer and A. Leauthaud and D. Maccagni and C. Marinoni and H. J. McCracken and P. Memeo and C. Porciani and R. Scaramella and C. Scarlata and N. Scoville},
journal= {arXiv preprint arXiv:0907.5416},
year = {2015}
}
Comments
Revised version, accepted for publication on Astronomy and Astrophysics