The Milky and its Gas: Cold Fountains and Accretion

TL;DR

This paper discusses how the Milky Way gains gas through high-velocity clouds like the Smith Cloud, which contribute low-metallicity gas to the galaxy, influencing its evolution.

Contribution

It provides new insights into the role of high-velocity clouds, especially the Smith Cloud, in galaxy gas accretion and star formation processes.

Findings

The Smith Cloud contains over 10^6 solar masses of low-metallicity gas.

High-velocity clouds are a significant source of gas accretion for the Milky Way.

The Smith Cloud may be part of a larger gas stream feeding the galaxy.

Abstract

The Milky Way is acquiring gas from infalling high-velocity clouds. The material enters a disk-halo interface that in many places is populated with HI clouds that have been ejected from the disk through processes linked to star formation. The Smith Cloud is an extraordinary example of a high-velocity cloud that is bringing $>10^6$ M$_{\odot}$ of relatively low metallicity gas into the Milky Way. It may be part of a larger stream, components of which are now passing through the disk.