The evolution of the baryon fraction in halos as a cause of scatter in the galaxy stellar mass in the EAGLE simulation

Understand

The EAGLE simulation suite has previously been used to investigate the relationship between the stellar mass of galaxies, $M_{*}$, and the properties of dark matter halos, using the hydrodynamical reference simulation combined with a dark matter only (DMO) simulation having identical initial conditions.

• The stellar masses of central galaxies in halos with $M_{\mathrm{200c}} > 10^{11} \mathrm{M_{\odot}}$ were shown to correlate with the DMO halo maximum circular velocity, with $\approx 0.2$ dex of scatter that is uncorrelated with other DMO halo properties.
• Here we revisit the origin of the scatter in the $M_{*}-V_{\mathrm{max, DMO}}$ relation in EAGLE at $z = 0.1$.
• We find that the scatter in $M_{*}$ correlates with the mean age of the galaxy stellar population such that more massive galaxies at fixed $V_{\mathrm{max, DMO}}$ are younger.