Gas-regulation of galaxies: the evolution of the cosmic sSFR, the metallicity-mass-SFR relation and the stellar content of haloes

Understand

A very simple physical model of galaxies, in which the formation of stars is instantaneously regulated by the mass of gas in a reservoir, links together three different aspects of the evolving galaxy population:(a) the cosmic time evolution of the specific star-formation rate sSFR relative to the growth of haloes, (b) the gas-phase metallicities across the galaxy population and over cosmic time, and (c) the ratio of the stellar to dark matter mass of haloes.

• If the SFR efficiency and wind mass loading are constant, the sSFR is set to the specific accretion rate of the galaxy: more realistic situations lead to an sSFR which is perturbed from this identity.
• The metallicity is set by the instantaneous operation of the regulator system rather than by the past history of the system.
• The regulator system naturally produces a Z(mstar, SFR) relation, with SFR as a second parameter in the mass-metallicity relation.