1209.3665 (F. Combes et al.)

Gas Fraction and Star Formation Efficiency at z < 1.0    [PDF]

F. Combes, S. Garcia-Burillo, J. Braine, E. Schinnerer, F. Walter, L. Colina

After new observations of 39 galaxies at z ~ 0.6-1.0 obtained at the IRAM 30m telescope, we present our full CO line survey covering the redshift range 0.2 < z < 1. Our aim is to determine the driving factors accounting for the steep decline of the star formation rate during this epoch. We study both the gas fraction, defined as M_gas/(M_gas+M_star), and the star formation efficiency (SFE) defined by the ratio between far-infrared luminosity and molecular gas mass (L_FIR/M_H2), i.e. a measure for the inverse of the gas depletion time. The sources are selected to be ultra-luminous infrared galaxies (ULIRGs), with L_FIR larger than 10^12 Lo, experiencing starbursts. Adopting a standard ULIRG CO-to-H2 conversion factor, their molecular gas depletion time is less than 100 Myr. Our full survey has now filled the gap of CO observations in the 0.2View original: http://arxiv.org/abs/1209.3665