Warm gas accretion onto the Galaxy
J. Bland-Hawthorn (University of Sydney)

TL;DR
This paper presents a hydrodynamical model showing that warm gas accretion, primarily from the Magellanic Stream, significantly contributes to the Galaxy's gas supply, with ionized gas playing a crucial role in ongoing accretion.
Contribution
The study introduces a new hydrodynamical model explaining H-alpha emissions and the disruption process of Stream clouds, highlighting the importance of warm ionized gas in galactic accretion.
Findings
Warm gas accretion rate is approximately 0.4 solar masses per year.
Disruption and ablation of Stream clouds lead to shock ionization and diffuse ionized gas.
The Magellanic Stream must be replenished continuously at a rate >0.1 Msun/yr.
Abstract
We present evidence that the accretion of warm gas onto the Galaxy today is at least as important as cold gas accretion. For more than a decade, the source of the bright H-alpha emission (up to 750 mR) along the Magellanic Stream has remained a mystery. We present a hydrodynamical model that explains the known properties of the H-alpha emission and provides new insights on the lifetime of the Stream clouds. The upstream clouds are gradually disrupted due to their interaction with the hot halo gas. The clouds that follow plough into gas ablated from the upstream clouds, leading to shock ionisation at the leading edges of the downstream clouds. Since the following clouds also experience ablation, and weaker H-alpha (100-200 mR) is quite extensive, a disruptive cascade must be operating along much of the Stream. In order to light up much of the Stream as observed, it must have a small…
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