Constraints on the Evolution of the Galaxy Stellar Mass Function II: Quenching Timescale of Galaxies and its Implication for their Star Formation Rate

Abstract

We study the connection between the observed star formation rate-stellar mass (SFR-$M_*$) relation and the evolution of the stellar mass function (SMF) by means of a subhalo abundance matching technique coupled to merger trees extracted from a N-body simulation. Our approach consist of forcing the model to match the observed SMF at redshift $z \sim 2.3$, and let it evolve down to $z \sim 0.3$ according to a $τ$ model, an exponentially declining functional form which describes the star formation rate decay of both satellite and central galaxies. In this study, we use three different sets of SMFs: ZFOURGE data from Tomczak et al.; UltraVISTA data from Ilbert et al. and COSMOS data from Davidzon et al. We also build a mock survey combining UltraVISTA with ZFOURGE. Our modelling of quenching timescales is consistent with the evolution of the SMF down to $z \sim 0.3$, with different accuracy depending on the particular survey used for calibration. We tested our model against the observed SMFs at low redshift and it predicts residuals (observation versus model) within $1σ$ observed scatter along most of the stellar mass range investigated, and with mean residuals below 0.1 dex in the range $\sim [10^{8.7}-10^{11.7}] M_{\odot}$. We then compare the SFR-$M_*$ relation predicted by the model with the observed one at different redshifts. The predicted SFR-$M_*$ relation underpredicts the median SFR at fixed stellar mass relative to observations at all redshifts. Nevertheless, the shapes are consistent with the observed relations up to intermediate-mass galaxies, followed by a rapid decline for massive galaxies.