Star formation in a diffuse high-altitude cloud?

TL;DR

This study investigates star formation in a high-altitude diffuse cloud, using multi-wavelength data to estimate its distance and analyze its gas properties, revealing conditions conducive to star formation far above the Galactic plane.

Contribution

It provides the first plausible distance estimate for the high-latitude cloud HRK 81.4-77.8 and links its gas properties to potential star formation processes in the Galactic halo.

Findings

The cloud is approximately 400 pc above the Galactic plane.

Disbalance in density and pressure suggests cold gas compression.

Conditions may trigger molecular gas formation high above the disk.

Abstract

A recent discovery of two stellar clusters associated with the diffuse high-latitude cloud HRK 81.4-77.8 has important implications for star formation in the Galactic halo. We derive a plausible distance estimate to HRK 81.4-77.8 primarily from its gaseous properties. We spatially correlate state-of-the-art HI, far-infrared and soft X-ray data to analyze the diffuse gas in the cloud. The absorption of the soft X-ray emission from the Galactic halo by HRK 81.4-77.8 is used to constrain the distance to the cloud. HRK 81.4-77.8 is most likely located at an altitude of about 400 pc within the disk-halo interface of the Milky Way Galaxy. The HI data discloses a disbalance in density and pressure between the warm and cold gaseous phases. Apparently, the cold gas is compressed by the warm medium. This disbalance might trigger the formation of molecular gas high above the Galactic plane on pc to sub-pc scales.