2007A&A...472..403T

The VIMOS VLT Deep Survey (VVDS) was undertaken to map the evolution of galaxies, large scale structures, and active galaxy nuclei from the redshift spectroscopic measurements of ∼10⁵ objects down to an apparent magnitude I_AB=24, in combination with a multi-wavelength acquisition for radio, infrared, optical, ultraviolet, and X-rays data. We present the evolution of the comoving star formation rate (SFR) density in the redshift range 0<z<5 using the first epoch data release of the VVDS, that is 11564 spectra over 2200arcmin² in two fields of view, the VVDS-0226-04 and the VVDS-CDFS-0332-27, and the cosmological parameters (Ω_M,Ω_Λ,h)=(0.3,0.7,0.7). We study the multi-wavelength non dust-corrected luminosity densities at 0<z<2 from the rest-frame far ultraviolet to the optical passbands, and the rest-frame 1500Å luminosity functions and densities at 2.7<z<5. They evolve from z=1.2 to z=0.05 according to (1+z)^x with x=2.05, 1.94, 1.92, 1.14, 0.73, 0.42, and 0.30 in the FUV-1500, NUV-2800, U-3600, B-4400, V-5500, R-6500, and I-7900 passbands, respectively. From z=1.2 to z=0.2 the B-band density for the irregular-like galaxies decreases markedly by a factor 3.5 while it increases by a factor 1.7 for the elliptical-like galaxies. We identify several SFR periods; from z=5 to 3.4 the FUV-band density increases by at most 0.5dex, from z=3.4 to 1.2 it decreases by 0.08dex, from z=1.2 to z=0.05 it declines steadily by 0.6dex. For the most luminous M_AB(1500Å)←21 galaxies the FUV-band density drops by 2dex from z=3.9 to z=1.2, and for the intermediate -21<M_AB(1500Å)←20 galaxies it drops by 2 dex from z=0.2 to z=0. Comparing with dust corrected surveys, at 0.4≲z≲2 the FUV seems obscured by a constant factor of ∼1.8-2mag, while at z<0.5 it seems progressively less obscured by up to ∼0.9-1mag when the dust-deficient early-type population is increasingly dominating the B-band density. The VVDS results agree with a downsizing picture where the most luminous sources cease to efficiently produce new stars 12Gyrs ago (at z≃4), while intermediate luminosity sources keep producing stars until 2.5Gyrs ago (at z≃0.2). A modest contribution of dry mergers and morphologies evolving towards early-type galaxies might contribute to increase the number density of the bright early types at z<1.5. Our observed SFR density is not in agreement with a continuous smooth decrease since z∼4.