THE BUILDUP OF THE HUBBLE SEQUENCE IN THE COSMOS FIELD
- Institute for Astronomy, ETH Zurich, 8092 Zurich (Switzerland)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
- California Institute of Technology, MS 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
- AIM Unite Mixte de Recherche CEA CNRS, Universite Paris VII UMR n158, Paris (France)
- INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
- Astronomy Department, University of California, Berkeley, CA 94705 (United States)
- Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
- Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12 (France)
- STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- LBNL and BCCP, University of California, Berkeley, CA 94720 (United States)
- Service d'Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette (France)
We use {approx}8600 COSMOS galaxies at mass scales >5 x 10{sup 10} M {sub sun} to study how the morphological mix of massive ellipticals, bulge-dominated disks, intermediate-bulge disks, disk-dominated galaxies, and irregular systems evolves from z = 0.2 to z = 1. The morphological evolution depends strongly on mass. At M > 3 x 10{sup 11} M {sub sun}, no evolution is detected in the morphological mix: ellipticals dominate since z = 1, and the Hubble sequence has quantitatively settled down by this epoch. At the 10{sup 11} M {sub sun} mass scale, little evolution is detected, which can be entirely explained by major mergers. Most of the morphological evolution from z = 1 to z = 0.2 takes place at masses 5 x 10{sup 10}-10{sup 11} M {sub sun}, where (1) the fraction of spirals substantially drops and the contribution of early types increases. This increase is mostly produced by the growth of bulge-dominated disks, which vary their contribution from {approx}10% at z = 1 to >30% at z = 0.2 (for comparison, the elliptical fraction grows from {approx}15% to {approx}20%). Thus, at these masses, transformations from late to early types result in diskless elliptical morphologies with a statistical frequency of only 30%-40%. Otherwise, the processes which are responsible for the transformations either retain or produce a non-negligible disk component. (2) The disk-dominated galaxies, which contribute {approx}15% to the intermediate-mass galaxy population at z = 1, virtually disappear by z = 0.2. The merger rate since z = 1 is too low to account for the disappearance of these massive disk-dominated systems, which most likely grow a bulge via secular evolution.
- OSTI ID:
- 21305016
- Journal Information:
- Astrophysical Journal Letters, Vol. 714, Issue 1; Other Information: DOI: 10.1088/2041-8205/714/1/L47; Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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