Matching the Evolution of the Stellar Mass Function Using Log-normal Star Formation Histories

Abstract

We show that a model consisting of individual, log-normal star formation histories for a volume-limited sample of $z\approx0$ galaxies reproduces the evolution of the total and quiescent stellar mass functions at $z\lesssim2.5$ and stellar masses $M_*\geq10^{10}\,{\rm M_\odot}$. This model has previously been shown to reproduce the star formation rate/stellar mass relation (${\rm SFR}$--$M_*$) over the same interval, is fully consistent with the observed evolution of the cosmic ${\rm SFR}$ density at $z\leq8$, and entails no explicit "quenching" prescription. We interpret these results/features in the context of other models demonstrating a similar ability to reproduce the evolution of (1) the cosmic ${\rm SFR}$ density, (2) the total/quiescent stellar mass functions, and (3) the ${\rm SFR}$--$M_*$ relation, proposing that the key difference between modeling approaches is the extent to which they stress/address diversity in the (starforming) galaxy population. Finally, we suggest that observations revealing the timescale associated with dispersion in ${\rm SFR}(M_*)$ will help establish which models are the most relevant to galaxy evolution.