Ionized absorbers as evidence for supernova-driven cooling of the lower Galactic corona

TL;DR

This paper proposes that supernova-driven feedback causes mixing and cooling in the Milky Way's lower corona, leading to gas accretion onto the disk, which sustains star formation.

Contribution

It introduces a new model where supernova feedback induces cooling and accretion in the galactic corona, explaining how hot-mode accretion feeds star formation.

Findings

Ultraviolet absorption features are consistent with a layer a few kpc above the disk.

Supernova feedback facilitates mixing and cooling of the corona.

Estimated accretion rate is a few solar masses per year.

Abstract

We show that the ultraviolet absorption features, newly discovered in HST spectra, are consistent with being formed in a layer that extends a few kpc above the disk of the Milky Way. In this interface between the disk and the Galactic corona, high-metallicity gas ejected from the disk by supernova feedback can mix efficiently with the virial-temperature coronal material. The mixing process triggers the cooling of the lower corona down to temperatures encompassing the characteristic range of the observed absorption features, producing a net supernova-driven gas accretion onto the disk at a rate of a few Msun/yr. We speculate that this mechanism explains how the hot-mode of cosmological accretion feeds star formation in galactic disks.