A multiwavelength study of Galactic HII region Sh2-294

TL;DR

This study combines multiwavelength observations to analyze the structure, stellar content, and star formation activity of the Galactic HII region S294, revealing a partially embedded cluster, an anomalous dust reddening law, and evidence of triggered star formation.

Contribution

It provides a comprehensive multiwavelength analysis of S294, including new insights into its dust properties, ionizing sources, and star formation processes, which were not previously characterized in detail.

Findings

Identified the ionizing star as approximately B0 V type.

Detected a partially embedded cluster and a small cluster at the border.

Evidence suggests star formation is triggered by HII region expansion.

Abstract

We present the observational results of Galactic HII region S294, using optical photometry, narrow-band imaging and radio continuum mapping at 1280 MHz, together with archival data from 2MASS, MSX and IRAS surveys. The stellar surface density profile indicates that the radius of the cluster associated with the S294 region is ~ 2.3 arcmin. We found an anomalous reddening law for the dust inside the cluster region and the ratio of total-to-selective extinction is found to be 3.8+-0.1. We estimate the minimum reddening E (B-V) = 1.35 mag and distance of 4.8+-0.2 kpc to the region from optical CC and CM diagrams. We identified the ionizing source of the HII region, and spectral type estimates are consistent with a star of spectral type ~ B0 V. The 2MASS JHKs images reveal a partially embedded cluster associated with the ionizing source along with a small cluster towards the eastern border of S294. The ionization front seen along the direction of small cluster in radio continuum and Halpha images, might be due to the interaction of ionizing sources with the nearby molecular cloud. We found an arc shaped diffuse molecular hydrogen emission at 2.12 micron and a half ring of MSX dust emission which surrounds the ionized gas in the direction of the ionization front. Self consistent radiative transfer model of mid- to far-infrared continuum emission detected near small cluster is in good agreement with the observed spectral energy distribution of a B1.5 ZAMS star. The morphological correlation between the ionised and molecular gas, along with probable time scale involved between the ionising star, evolution of HII region and small cluster, indicates that the star-formation activity observed at the border is probably triggered by the expansion of HII region.