Shaping the galaxy stellar mass function with supernova- and AGN-driven winds

TL;DR

This paper presents a new energy-driven outflow model for galaxy formation simulations that accurately reproduces the observed galaxy stellar mass function across different masses and redshifts by incorporating feedback from supernovae and AGN.

Contribution

The study introduces a wind model with decreasing velocity and increasing mass loading in low-mass galaxies, improving the match to observed galaxy properties and evolution.

Findings

Accurately reproduces the low-mass end of the galaxy stellar mass function.

Matches observed stellar mass functions at redshifts z=1 and z=2.

Aligns with observed gas-to-stellar mass ratios and star formation rates.

Abstract

Cosmological hydrodynamical simulations of galaxy formation in representative regions of the Universe typically need to resort to subresolution models to follow some of the feedback processes crucial for galaxy formation. Here, we show that an energy-driven outflow model in which the wind velocity decreases and the wind mass loading increases in low-mass galaxies, as suggested by observations, can produce a good match to the low-mass end of the observed galaxy stellar mass function. The high-mass end can be recovered simultaneously if feedback from active galactic nuclei (AGN) and a correction for diffuse stellar light plausibly missed in observations are included. At the same time, our model is in good agreement with the stellar mass functions at redshifts z=1 and z=2, and with the observed redshift evolution of the cosmic star formation rate density. In addition, it accurately reproduces the observed gas to stellar mass ratios and specific star formation rates of galaxies as a function of their stellar mass. This agreement with a diverse set of data marks significant progress in hydrodynamically modelling the formation of a representative galaxy population. It also suggests that the mass flux in real galactic winds should strongly increase towards low-mass galaxies. Without this assumption, an overproduction of galaxies at the faint-end of the galaxy luminosity function seems inevitable in our models.