The stellar mass function and star formation rate–stellar mass relation of galaxies at z ∼ 4–7

We investigate the evolution of the star formation rate–stellar mass relation (SFR–M ⋆) and galaxy stellar mass function (GSMF) of z ∼ 4–7 galaxies, using cosmological simulations run with the smoothed particle hydrodynamics code P-GADGET3(XXL). We explore the effects of different feedback prescriptions (supernova-driven galactic winds and AGN feedback), initial stellar mass functions and metal cooling. We show that our fiducial model, with strong energy-driven winds and early active galactic nuclei (AGN) feedback, is able to reproduce the observed stellar mass function obtained from Lyman-break selected samples of star-forming galaxies at redshift 6 ≤ z ≤ 7. At z ∼ 4, observed estimates of the GSMF vary according to how the sample was selected. Our simulations are more consistent with recent results from K-selected samples, which provide a better proxy of stellar masses and are more complete at the high-mass end of the distribution. We find that in some cases simulated and observed SFR–M ⋆ relations are in tension, and this can lead to numerical predictions for the GSMF in excess of the GSMF observed. By combining the simulated SFR(M ⋆) relationship with the observed star formation rate function at a given redshift, we argue that this disagreement may be the result of the uncertainty in the SFR–M ⋆ (L UV–M ⋆) conversion. Our simulations predict a population of faint galaxies not seen by current observations.