The VIMOS-VLT deep survey luminosity dependence of clustering at z ≃ 1

We investigate the dependence of galaxy clustering on the galaxy intrinsic luminosity at high redshift, using the data from the First Epoch VIMOS-VLT Deep Survey (VVDS). The size (6530 galaxies) and depth (I_AB < 24) of the survey allows us to measure the projected two-point correlation function of galaxies, w_p(r_p), for a set of volume-limited samples up to an effective redshift (z) = 0.9 and median absolute magnitude -19.6 < MB < -21.3. Fitting w_p(r_p) with a single power-law model for the real-space correlation function ξ(r) = (r/r₀)-γ, we measure the relationship of the correlation length r₀ and the slope γ with the sample median luminosity for the first time at such high redshift. Values from our lower-redshift samples (0.1 < z < 0.5) are fully consistent with the trend observed by larger local surveys. In our high redshift sample (0.5 < z < 1.2), we find that the clustering strength suddenly rises around M*_B, apparently with a sharper inflection than at low redshifts. Galaxies in the faintest sample ((M_B) = -19.6) have a correlation length r₀ =2.7_-0.3 ^+0.3h^-1Mpc, compared to r₀ = 5.0 _-1.6^+1.5h^-1 Mpc at (M_B) = -21.3. The slope of the correlation function is observed to correspondingly steepen significantly from γ = 1.6_-0.1 ^+0.1to γ= 2.4_-0.2^+0.4 This is not observed either by large local surveys or in our lower-redshift samples and seems to imply a significant change in the way luminous galaxies trace dark-matter halos at z ∼ 1 with respect to z ∼ 0. At our effective median redshift z ≃ 0.9 this corresponds to a strong difference of the relative bias, from b/b* < 0.7 for galaxies with L < L* to b/b* ≃ 1.4 for galaxies with L > L*.