The galaxy halo connection in modified gravity cosmologies : environment dependence of galaxy luminosity function.

We investigate the dependence of the galaxy–halo connection and galaxy density field in modified gravity models using the N-body simulations for f(R) and nDGP models at z = 0. Because of the screening mechanisms employed by these models, chameleon and Vainshtein, haloes are clustered differently in the non-linear regime of structure formation. We quantify their deviations in the galaxy density field from the standard Λ cold dark matter (ΛCDM) model under different environments. We populate galaxies in haloes via the (sub)halo abundance matching. Our main results are as follows: (1) The galaxy–halo connection strongly depends on the gravity model; a maximum variation of ∼40 per cent is observed between halo occupational distribution (HOD) parameters; (2) f(R) gravity models predict an excess of galaxies in low-density environments of ∼10 per cent but predict a deficit of ∼10 per cent at high-density environments for |fR0| = 10−4 and 10−6 while |fR0| = 10−5 predicts more high-density structures; nDGP models are consistent with ΛCDM; (3) different gravity models predict different dependences of the galaxy luminosity function (GLF) with the environment, especially in void-like regions we find differences around ∼10 per cent for the f(R) models while nDPG models remain closer to ΛCDM for low-luminosity galaxies but there is a deficit of ∼11 per cent for high-luminosity galaxies in all environments. We conclude that the dependence of the GLF with environment might provide a test to distinguish between gravity models and their screening mechanisms from the ΛCDM. We provide HOD parameters for the gravity models analysed in this paper