The environs of the ultracompact HII region G45.45+0.06

TL;DR

This study investigates the larger environment of the ultracompact HII region G45.45+0.06, revealing a larger HII region G45L, its molecular gas, potential ionizing stars, and star formation activity, suggesting possible triggered star formation.

Contribution

It provides the first large-scale multiwavelength analysis of the G45.45+0.06 region, identifying a new larger HII region G45L and its role in star formation.

Findings

G45L is a larger HII region surrounding G45.45+0.06.

G45L contains potential O-type stars and YSO candidates.

G45L may have triggered star formation in the region.

Abstract

G45.45+0.06 is an ultra-compact HII (UCHII) region extensively studied. It is known that G45.45+0.06 is embedded in a complex of UCHII regions, but up the date, the surrounding ISM in a larger spatial scale has not been analyzed. Using data from large-scale surveys: Two Micron All Sky Survey, GLIMPSE, MIPSGAL, MAGPIS and GRS, we performed a multiwavelength study of a region about 7' x 7'in the vicinity of G45.45+0.06. We found that the UCHII complex lies in a border of a larger (diameter of ~ 3') and fainter HII region, which is located at the same distance as G45.45+0.06, ~ 8 kpc. In this work, this larger HII region was called G45L. A good morphological correlation is observed between the PDRs and the molecular gas mapped in the 13CO J=1--0 and CS J=2--1 lines, suggesting that G45L may be collecting the molecular material. From a near- and mid-IR photometric study, we found three sources, likely O-type stars, that are possibly responsible for the creation of G45L. Additionally we found several YSO candidates lying preferently in the molecular shell that surrounds G45L. Our results confirm that the region southeastern the UCHII complex where G45.45+0.06 is embedded and eastern G45L is active in star formation. We suggest that G45L has been expanding during about 2 x 10^6 yr and could have triggered the formation of the zero-age main sequence stars that are ionizing the UCHII region G45.45+0.06. However we can not discard that both HII regions are coeval.