The impact of stellar feedback on the structure, size and morphology of galaxies in Milky Way size dark matter haloes

TL;DR

This study uses cosmological simulations to show that efficient stellar feedback is crucial for forming realistic late-type galaxies with proper sizes, morphologies, and angular momentum, matching observations.

Contribution

It demonstrates that locally efficient star formation and vigorous feedback are essential for realistic galaxy formation in Milky Way-sized halos, highlighting feedback's dual role.

Findings

Efficient feedback produces realistic late-type galaxy properties.

Low-efficiency feedback results in irregular, overly extended galaxies.

Vigorous feedback maintains low baryon concentration and angular momentum.

Abstract

We use cosmological zoom-in simulations of galaxy formation in a Milky Way (MW)-sized halo started from identical initial conditions to investigate the evolution of galaxy sizes, baryon fractions, morphologies and angular momenta in runs with different parameters of the star formation--feedback cycle. Our fiducial model with a high local star formation efficiency, which results in efficient feedback, produces a realistic late-type galaxy that matches the evolution of basic properties of late-type galaxies: stellar mass, disk size, morphology dominated by a kinematically cold disk, stellar and gas surface density profiles, and specific angular momentum. We argue that feedback's role in this success is twofold: (1) removal of low-angular momentum gas and (2) maintaining a low disk-to-halo mass fraction which suppresses disk instabilities that lead to angular momentum redistribution and a central concentration of baryons. However, our model with a low local star formation efficiency, but large energy input per supernova, chosen to produce a galaxy with a similar star formation history as our fiducial model, leads to a highly irregular galaxy with no kinematically cold component, overly extended stellar distribution and low angular momentum. This indicates that only when feedback is allowed to become vigorous via locally efficient star formation in dense cold gas, resulting galaxy sizes, gas/stellar surface density profiles and stellar disk angular momenta agree with observed $z=0$ galaxies.