The zCOSMOS redshift survey: evolution of the light in bulges and discs since z ~ 0.8^⋆

¹ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
e-mail: lidia.tasca@oamp.fr
² Institute of Astronomy, ETH Zurich, 8093 Zurich, Switzerland
³ INAF Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁴ Centro de Estudios de Física del Cosmos de Aragón, plaza San Juan 1, planta 2, 44001 Teruel, Spain
⁵ Kavli Institute for Astronomy and Astrophysics, Peking University, 100871 Beijing, PR China
⁶ The Observatories of the Carnegie Institution for Science, 813 Santa Barbara street, Pasadena CA 91101, USA
⁷ University of Sussex, Falmer, Brighton BN1 9QH, UK
⁸ INAF Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
⁹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, USA
¹⁰ Astrophysical Observatory, City University of New York, College of Staten Island, 2800 Victory Blvd, Staten Island NY 10314, USA
¹¹ Institute for Computational Cosmology, Durham University, South Road, Durham, UK
¹² INAF – Osservatorio Astronomico di Padova, Padova, Italy
¹³ Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, 790-8577 Matsuyama, Japan
¹⁴ Department of Physiscs, Oxford University, Denis Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹⁵ Institut de Recherche en Astrophysique et Planétologie, CNRS, 14 avenue Edouard Belin, 31400 Toulouse, France
¹⁶ IRAP, Université de Toulouse, UPS-OMP, 31400 Toulouse, France
¹⁷ LASTRO, Ecole polytechnique fédérale de Lausanne, 1015 Lausane, Suisse
¹⁸ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
¹⁹ INAF – IASF, via Bassini 15, 20133 Milano, Italy
²⁰ Max – Planck – Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching bei Munchen, Germany
²¹ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
²² Instituto de Astrofísica de Andalucía, CSIC, Apartado de correos 3004, 18080 Granada, Spain
²³ Department of Physics and Astronomy, University of California, Los Angeles CA 90095-1547, USA
²⁴ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
²⁵ INAF – IASF Bologna, via P. Gobetti 101, 40129 Bologna, Italy
²⁶ Dipartimento di Astronomia, Università degli Studi di Bologna, 40126 Bologna, Italy
²⁷ Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98 bis boulevard Arago, 75014 Paris, France
²⁸ Institute for Astronomy, 2680 Woodlawn Drive, Honolulu HI 96822-1839, USA
²⁹ North America ALMA Science Center, National Radio Astronomy Observatory, USA

Received: 23 February 2014
Accepted: 13 March 2014

Abstract

We studied the chronology of galactic bulge and disc formation by analysing the relative contributions of these components to the B-band rest-frame luminosity density at different epochs. We present the first estimate of the evolution of the fraction of rest-frame B-band light in galactic bulges and discs since redshift z ~ 0.8. We performed a bulge-to-disc decomposition of HST/ACS images of 3266 galaxies in the zCOSMOS-bright survey with spectroscopic redshifts in the range 0.7 ≤ z ≤ 0.9. We find that the fraction of B-band light in bulges and discs is (26 ± 4)% and (74 ± 4)%, respectively. When compared with rest-frame B-band measurements of galaxies in the local Universe in the same mass range (), we find that the B-band light in discs decreases by ~30% from z ~ 0.7−0.9 to z ~ 0, while the light from the bulge increases by ~30% over the same period of time. We interpret this evolution as the consequence of star formation and mass assembly processes, as well as morphological transformation, which gradually shift stars formed at half the age of the Universe from star-forming late-type/irregular galaxies to earlier types and ultimately into spheroids.