2012A&A...546A..96O

This work aims at investigating the molecular gas in the surroundings of the ultra-compact HII region G045.47+0.05 looking for evidence of molecular outflows.We carried out observations towards a region of 2'x2' centered at RA=19:14:25.6, Dec=+11:09:27.6 (J2000) using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in the ¹²CO J=3-2, ¹³CO J=3-2, HCO⁺ J=4-3, and CS J=7-6 lines with an angular resolution of 22''. We complement these observations with public infrared data. We characterize the physical parameters of the molecular clump where G045.47+0.0 is embedded. The detection of the CS J=7-6 line emission in the region reveals that the ultra-compact HII region G045.47+0.0 has not completely disrupted the dense gas where it was born. The HCO⁺ abundance observed towards G045.47+0.0 suggests there is molecular outflow activity in the region. From the analysis of the ¹²CO J=3-2 transition we report bipolar molecular outflows with a total mass of about 300M_☉. We derive a dynamical time (flow's age) of about 10⁵yr for the outflow gas, in agreement with the presence of an ultra-compact HII region. We identify the source 2MASS 19142564+1109283 as the massive protostar candidate to drive the molecular outflows. Based on the analysis of its spectral energy distribution, we infer that it is an early B-type star of about 15M_☉. The results of this work support the scenario where the formation of massive stars, at least up to early B-type stars, is similar to that of low-mass stars.