A Reservoir of Ionized Gas in the Galactic Halo to Sustain Star Formation in the Milky Way

TL;DR

This study uses Hubble observations to identify ionized high-velocity clouds in the Milky Way's halo, revealing their distances and potential to sustain ongoing star formation.

Contribution

It provides new measurements of the distances and masses of ionized high-velocity clouds, clarifying their role in fueling star formation in the Galaxy.

Findings

iHVCs with 90 < |v_LSR| < 170 km/s are within one Galactic radius.

These iHVCs have sufficient mass to sustain star formation.

Higher velocity iHVCs (>170 km/s) are at larger distances and may be infalling material.

Abstract

Without a source of new gas, our Galaxy would exhaust its supply of gas through the formation of stars. Ionized gas clouds observed at high velocity may be a reservoir of such gas, but their distances are key for placing them in the Galactic halo and unraveling their role. We have used the Hubble Space Telescope to blindly search for ionized high-velocity clouds (iHVCs) in the foreground of Galactic stars. We show that iHVCs with 90 < |v_LSR| < 170 km/s are within one Galactic radius of the sun and have enough mass to maintain star formation, while iHVCs with |v_LSR|>170 km/s are at larger distances. These may be the next wave of infalling material.