Stellar Feedback and the Energy Budget of Late-Type Galaxies: Missing Baryons and Core Creation

TL;DR

This study investigates the role of supernova feedback in galaxy formation, showing it can heat or create cores in dark matter halos and account for the missing baryons mostly in hot gas around late-type galaxies.

Contribution

It provides a detailed analysis linking supernova energy to baryon heating and core formation, highlighting the efficiency of feedback processes in galaxy evolution.

Findings

Supernova feedback can heat missing baryons to virial temperature.

Feedback energy is sufficient to transform cusps into cores.

Most baryons are in hot gas surrounding galaxies.

Abstract

In a $\Lambda$CDM cosmology, galaxy formation is a globally inefficient process: it is often the case that far fewer baryons are observed in galaxy disks than expected from the cosmic baryon fraction. The location of these "missing baryons" is unclear. By fitting halo profiles to the rotation curves of galaxies in the SPARC data set, we measure the "missing baryon" mass for individual late-type systems. Assuming that haloes initially accrete the cosmological baryon fraction, we show that the maximum energy available from supernovae is typically not enough to completely eject these "missing baryons" from a halo, but it is often sufficient to heat them to the virial temperature. The energy available from supernovae has the same scaling with galaxy mass as the energy needed to heat or eject the "missing baryons", indicating that the coupling efficiency of the feedback to the ISM may be constant with galaxy virial mass. We further find that the energy available from supernova feedback is always enough to convert a primordial cusp into a core and has magnitude consistent with what is required to heat the "missing baryons" to the virial temperature. Taking a census of the baryon content of galaxies with ${\rm 10^9<M_{vir}/M_{\odot}<10^{12}}$ reveals that $\sim86\%$ of baryons are likely to be in a hot phase surrounding the galaxies and possibly observable in the X-ray, $\sim7\%$ are in the form of cold gas, and $\sim7\%$ are in stars.