Precipitation-Regulated Star Formation in Galaxies

TL;DR

This paper proposes that the observed scaling relations in galaxies can be explained by a feedback mechanism where heating of circumgalactic gas in response to cold cloud precipitation regulates star formation and galaxy properties.

Contribution

It introduces a unifying model where precipitation-regulated feedback naturally explains key galaxy scaling relations, simplifying complex galaxy evolution processes.

Findings

Scaling relations emerge from precipitation-regulated feedback.

Feedback suspends gas in a marginally precipitating state.

Model explains correlations between stellar mass, total mass, and black hole mass.

Abstract

Galaxy growth depends critically on the interplay between radiative cooling of cosmic gas and the resulting energetic feedback that cooling triggers. This interplay has proven exceedingly difficult to model, even with large supercomputer simulations, because of its complexity. Nevertheless, real galaxies are observed to obey simple scaling relations among their primary observable characteristics. Here we show that a generic emergent property of the interplay between cooling and feedback can explain the observed scaling relationships between a galaxy's stellar mass, its total mass, and its chemical enrichment level, as well as the relationship between the average orbital velocity of its stars and the mass of its central black hole. These relationships naturally result from any feedback mechanism that strongly heats a galaxy's circumgalactic gas in response to precipitation of colder clouds out of that gas, because feedback then suspends the gas in a marginally precipitating state.