The stellar content of UCHII regions: the molecular cloud GRSMC045.49+00.05

Abstract

Ultra-compact Hii (UCHII) regions are an important phase in the formation and early evolution of massive stars. The main objectives of this work are to study the stellar content associated with the G045.49+00.04 and G045.14+00.14 star-forming regions located in the GRSMC45.46+0.05 molecular cloud at a distance of about 8kpc. Both regions contain a number of UCHII regions. The main objective is to characterize the embedded young stellar objects (YSOs), such as their mass, evolutionary age and age spread, spatial distribution, luminosity function. We used near-, mid-, and far-infrared photometric data to identify and classify the YSOs. Their main parameters were determined by the spectral energy distribution (SED) fitting tool using radiation transfer models. Totally, we identified 2864 YSOs. We also constructed a colour-magnitude diagram to compare the parameters of stellar objects with the results of the radiative transfer models. The density distribution of the identified YSOs showed the presence of dense clusters in the UCHII regions. The parameters of YSOs in the IRAS clusters and non-cluster objects surrounding them show some differences. In general, the YSOs in these clusters have an evolutionary age larger than 106 years with an age spread of a few Myr. The clusters include several high- and intermediate-mass zero-age main sequence stellar objects. The small age spread suggests that the clusters may originate from a single triggering event.