Neutral hydrogen in galactic fountains

TL;DR

This study uses simulations of a Milky Way-like galaxy with supernova-driven galactic fountains to replicate observed neutral hydrogen features, including velocity distributions and high-velocity clouds, matching real survey data.

Contribution

It demonstrates that supernova-driven galactic fountains can reproduce observed HI properties and high-velocity clouds in a Milky Way-like galaxy.

Findings

Simulated HI disk matches observed extent and brightness.

High-velocity clouds in simulations resemble those observed, including their distribution.

Galactic fountain cycles matter at about 0.5 solar masses per year.

Abstract

Simulations of an isolated Milky Way-like galaxy, in which supernovae power a galactic fountain, reproduce the observed velocity and 21cm brightness statistics of galactic neutral hydrogen (HI). The simulated galaxy consists of a thin HI disk, similar in extent and brightness to that observed in the Milky Way, and extra-planar neutral gas at a range of velocities due to the galactic fountain. Mock observations of the neutral gas resemble the HI flux measurements from the Leiden-Argentine-Bonn (LAB) HI, survey, including a high-velocity tail which matches well with observations of high-velocity clouds. The simulated high-velocity clouds are typically found close to the galactic disk, with a typical line-of-sight distance of 13kpc from observers on the solar circle. The fountain efficiently cycles matter from the centre of the galaxy to its outskirts at a rate of around 0.5 M_sun/yr