Simulations of the galaxy population constrained by observations from z=3 to the present day: implications for galactic winds and the fate of their ejecta

TL;DR

This study uses advanced simulations constrained by observations from redshift 3 to today to improve understanding of galactic winds, feedback, and galaxy evolution, proposing a model with redshift- and mass-dependent reaccretion timescales.

Contribution

It introduces a novel model where galactic wind reaccretion timescales depend on halo mass and are redshift-independent, fitting galaxy observations across all redshifts.

Findings

Reproduces observed galaxy abundances from z=0 to z=3.

Suggests reaccretion efficiency varies with halo mass and redshift.

Produces younger, bluer dwarf galaxies with improved clustering properties.

Abstract

We apply Monte Carlo Markov Chain (MCMC) methods to large-scale simulations of galaxy formation in a LambdaCDM cosmology in order to explore how star formation and feedback are constrained by the observed luminosity and stellar mass functions of galaxies. We build models jointly on the Millennium and Millennium-II simulations, applying fast sampling techniques which allow observed galaxy abundances over the ranges 7<log(M*/Msun)<12 and z=0 to z=3 to be used simultaneously as constraints in the MCMC analysis. When z=0 constraints alone are imposed, we reproduce the results of previous modelling by Guo et al. (2012), but no single set of parameters can reproduce observed galaxy abundances at all redshifts simultaneously, reflecting the fact that low-mass galaxies form too early and thus are overabundant at high redshift in this model. The data require the efficiency with which galactic wind ejecta are reaccreted to vary with redshift and halo mass quite differently than previously assumed, but in a similar way as in some recent hydrodynamic simulations of galaxy formation. We propose a specific model in which reincorporation timescales vary inversely with halo mass and are independent of redshift. This produces an evolving galaxy population which fits observed abundances as a function of stellar mass, B- and K-band luminosity at all redshifts simultaneously. It also produces a significant improvement in two other areas where previous models were deficient. It leads to present day dwarf galaxy populations which are younger, bluer, more strongly star-forming and more weakly clustered on small scales than before, although the passive fraction of faint dwarfs remains too high.