Context. 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 IAB = 24, in combination with a multi-wavelength acquisition for radio, infrared, optical, ultraviolet, and X-rays data. Aims. 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 2200 arcmin2 in two fields of view, the VVDS-0226-04 and the VVDS-CDFS-0332-27, and the cosmological parameters (ΩM, ΩΛ, h) = (0.3, 0.7,0.7). Methods. 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 1500 Åluminosity functions and densities at 2.7 < z < 5. Results. 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 irregularlike 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 0.5 dex, from z = 3.4 to 1.2 it decreases by 0.08 dex, from z = 1.2 to z = 0.05 it declines steadily by 0.6 dex. For the most luminous MAB(1500 Å) < -21 galaxies the FUV-band density drops by 2 dex from z = 3.9 to z = 1.2, and for the intermediate -21 < M AB(1500 Å) < -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 ∼ 1.8-2 mag, while at z < 0.5 it seems progressively less obscured by up to ∼0.9-l mag when the dust-deficient early-type population is increasingly dominating the 5-band density. Conclusions. The VVDS results agree with a downsizing picture where the most luminous sources cease to efficiently produce new stars 12 Gyrs ago (at z ≃4), while intermediate luminosity sources keep producing stars until 2.5 Gyrs 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.
Áreas temáticas de ASJC Scopus
- Astronomía y astrofísica
- Ciencias planetarias y espacial