Assessing the stellar population and the environment of an HII region on the far side of the Galaxy

TL;DR

This study examines a distant star formation region in the Galaxy, analyzing its stellar content, environment, and potential cluster association, supported by multi-wavelength observations and parallax measurements.

Contribution

It provides new insights into the stellar population and environment of a far-side HII region, including the identification of a potential young stellar cluster candidate.

Findings

Identification of a star cluster candidate near the HII region.

Detection of young stellar objects with high extinction.

Correlation between 13CO emission and mid-infrared features.

Abstract

We have investigated the stellar and interstellar content of the distant star formation region IRAS 17591-2228 (WISE HII region GAL 007.47+0.06). It is associated to a water maser, whose parallax distance is d=20.4^{+2.8} {-2.2} kpc, supported by independent measurements of proper motion and radial velocity. It is projected in the same direction as an extremely red (J-Ks ~ 6 mag) group of stars, and a shell of mid-infrared emission. We qualify the group of stars as a cluster candidate, VVV CL177. Its radius spans between 0.45' and 1' and contains at least two young stellar objects with an extreme extinction near Av ~ 40 mag. Yet more analysis will be required to determine is it is a real single cluster associated with the water maser. The 13CO emissions at the radial velocity of the maser corresponds to the mid-infrared emission.