The Milky Way Hot Baryons and their Peculiar Density Distribution: a Relic of Nuclear Activity

TL;DR

This study reveals that the Milky Way's hot baryonic gas extends from the disk to at least 200 kpc, showing a peculiar density peak likely linked to past nuclear activity, and updates the galaxy's total baryonic mass.

Contribution

It demonstrates the extensive distribution of hot baryons around the Milky Way and links their density profile to historical nuclear activity, updating the galaxy's baryonic mass estimate.

Findings

Hot gas extends to 200 kpc from the Galactic center.

Density peaks about 6 kpc from the center, indicating past activity.

Total baryonic mass is estimated at (0.8-4) x 10^11 solar masses.

Abstract

We know that our Galaxy is permeated by tenuous, hot, metal-rich gas. However much remains unknown about its origin, the portion of the Galaxy that it permeates, its total mass, as any role it may play in regulating activity in the Galaxy. In a Letter currently in the press with the ApJ, we show that this hot gas permeates both the disk of the Galaxy and a large spherical volume, centered on the Galactic nucleus, and extending out to distances of at least 60-200 kpc from the center. This gas displays a peculiar density distribution that peaks about 6 kpc from the Galaxy's center, likely witnessing a period of strong activity of the central super-massive black hole of the Milky Way that occurred 6 Myrs ago. With our study we are also able to update the total baryonic mass of the Galaxy to Mb = (0.8-4)x1e11 Solar Masses, sufficient to close the Galaxy's baryon census.