Stellar population in the vicinity of the H ii region G331.03-00.15

Abstract

We present a multi-wavelength study of the H ii region G331.03-00.15, with the aim of identifying the population of massive stars associated with it. The distributions of ionised gas and heated dust both exhibit similar spherical forms, while the bordering photo-dissociating region follows a very ring-like distribution, indicating the presence of abundant neighbouring molecular material being photo-dissociated. There is only one high-mass star catalogued in the region, namely, the WR star 1051-67L. Based on an energy analysis of the detected radio continuum emission, we deduced that additional high-mass stars could be interacting with G331.03-00.15. We conducted a search of massive star candidates by applying a series of colour criteria to a sample of highly reddened infrared (IR) point sources projected over the radio continuum morphology, with the additional condition that they be located at the same distance assumed for the region. Fourteen candidate sources were selected and classified using low-resolution, near-infrared (NIR) spectroscopic data in the H and K bands, obtained with Gemini/FLAMINGOS-2. We identified one massive star and classified it as an O7 V star. Adding the contribution from this new star to the total ionising radiation available, we concluded that it would be possible for the H ii region to be powered solely by these two massive stars. However, we do not rule out the possibility that there could be more early-type stars that remain undetected in this highly obscured part of the Galaxy. Additionally, we searched for primary tracers of star-forming activity and identified several class I and II candidate young stellar objects (YSOs), positioned over the dense clouds and clumps of molecular material found in the area. The presence of several maser species located in the densest cloud are also indicative of massive star formation taking place in the vicinity of G331.03-00.15.