GALAXY STELLAR MASS ASSEMBLY BETWEEN 0.2 < z < 2 FROM THE S-COSMOS SURVEY

Journal Article · Mon Feb 01 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/709/2/644· OSTI ID:21392315

Ilbert, O; Le Floc'h, E; Kartaltepe, J; Sanders, D B ^[1]; Salvato, M; Capak, P; Scoville, N ^[2]; Aussel, H ^[3]; McCracken, H J ^[4]; Mobasher, B ^[5]; Arnouts, S ^[6]; Bundy, K; Tasca, L ^[7]; Cassata, P; Kneib, J -P; Le Fevre, O ^[8]; Koekemoer, A ^[9]; Lilly, S ^[10]; Surace, J ^[11]; Taniguchi, Y ^[12]

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1. Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, HI 96822 (United States)
2. California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
3. AIM Unite Mixte de Recherche CEA CNRS, Universite Paris VII UMR n158, Paris (France)
4. Institut d'Astrophysique de Paris, UMR7095 CNRS, Universite Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris (France)
5. Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States)
6. Canada France Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States)
7. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Room 101, Toronto, ON M58 3H4 (Canada)
8. Laboratoire d'Astrophysique de Marseille, Universite de Provence, CNRS, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12 (France)
9. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
10. Department of Physics, ETH Zurich, CH-8093 Zurich (Switzerland)
11. Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
12. Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan)

We follow the galaxy stellar mass assembly by morphological and spectral type in the COSMOS 2 deg{sup 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{sub 3.6{mu}m} > 1 muJy with accurate photometric redshifts ({sigma}{sub (z{sub phot}-z{sub spec})/(1+z{sub spec})}=0.008 at i {sup +} < 22.5). Using a spectral classification, we find that z {approx} 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 {approx} 2.5 Gyr), but only by 0.3 dex between z = 0.8-1 and z {approx} 0.1 ({Delta}t {approx} 6 Gyr). Then, we add the morphological information and find that 80%-90% of the massive quiescent galaxies (log M {approx} 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 approx 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.

• OSTI ID: 21392315
• Journal Information: Astrophysical Journal, Vol. 709, Issue 2; Other Information: DOI: 10.1088/0004-637X/709/2/644; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CLASSIFICATION
GALACTIC EVOLUTION
GALAXIES
LUMINOSITY
MASS
MORPHOLOGY
RED SHIFT
STARS
UNIVERSE
EVOLUTION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES