Relation between stellar mass and star-formation activity in galaxies
For a mass-selected sample of 66544 galaxies with photometric redshifts (z phot) from the Cosmic Evolution Survey (COSMOS), we examine the evolution of star-formation activity as a function of stellar mass in galaxies. We estimate the cosmic star-formation rates (SFRs) over the range 0.2 < z phot < 1.2, using the rest-frame 2800 Å flux (corrected for extinction). We find the mean SFR to be a strong function of the galactic stellar mass at any given redshift, with massive systems (log(M/M☉) > 10.5) contributing less (by a factor of ~5) to the total star-formation rate density (SFRD). Combining data from the COSMOS and Gemini Deep Deep Survey, we extend the SFRD-z relation as a function of stellar mass to z ~ 2. For massive galaxies, we find a steep increase in the SFRD-z relation to z ~ 2; for the less-massive systems, the SFRD which also increases from z = 0 to 1 levels off at z ~ 1. This implies that the massive systems have had their major star-formation activity at earlier epochs (z > 2) than the lower-mass galaxies. We study changes in the SFRDs as a function of both redshift and stellar mass for galaxies of different spectral types. We find that the slope of the SFRD-z relation for different spectral types of galaxies is a strong function of their stellar mass. For low- and intermediate-mass systems, the main contribution to the cosmic SFRD comes from the star-forming galaxies while, for more-massive systems, the evolved galaxies are the most dominant population.
© 2009 The American Astronomical Society. Received 2008 April 8, accepted for publication 2008 August 18. Published 2008 December 2. Print publication: Issue 2 (2009 January 10). Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555; also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under cooperative agreement with the National Science Foundation; the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.; and the Canada-France-Hawaii Telescope with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the National Research Council of Canada, the Canadian Astronomy Data Centre, the Centre National de la Recherche Scientifique de France, TERAPIX and the University of Hawaii. Online-only material: color figure.
Published - MOBapj09.pdf