Evidence for environment - dependent galaxy Luminosity Function up to z = 1 . 5 in the VIMOS - VLT Deep Survey ⋆

We measure the evolution of the galaxy Luminosity Function as a function of large-scale environment up to z = 1.5 from the VIMOS-VLT Deep Survey (VVDS) first epoch data. The 3D galaxy density field is reconstructed using a gaussian filter of smoothing length 5h Mpc and a sample of 6582 galaxies with 17.5 ≤ IAB ≤ 24 and measured spectroscopic redshifts. We split the sample in four redshift bins up to z = 1.5 and in under-dense and over-dense environments according to the average density contrast δ = 0. There is a strong dependence of the Luminosity Function (LF) with large-scale environment up to z = 1.2: the LF shape is observed to have a steeper slope in under-dense environments. We find α = −1.32 ± 0.07,−1.35 ± 0.10,−1.42 ± 0.18 in under-dense environments and α = −1.08 ± 0.05,−1.06 ± 0.06, −1.22 ± 0.12 in over-dense environments in the redshift bins z =[0.25− 0.6], [0.6− 0.9], [0.9− 1.2], respectively using a best-fit Schechter luminosity function. We find a continuous brightening of ∆M∗ ∼ 0.6 mag from z = 0.25 to z = 1.5 both in under-dense and over-dense environments. The rest-frame B-band luminosity density continuously increases in under-dense environments from z = 0.25 to z = 1.5 whereas its evolution in over-dense environments presents a peak at z ∼ 0.9. We interpret the peak by a complex interplay between the decrease of the star formation rate and the increasing fraction of galaxies at δ > 0 due to hierarchical growth of structures. As the environmental dependency of the LF shape is already present at least up to z = 1.2, we therefore conclude that either the shape of the LF is imprinted very early on in the life of the Universe, a ‘nature’ process, or that ‘nurture’ physical processes shaping up environment relation have already been efficient earlier than a look-back time corresponding to 30% of the current age of the