Outflow activity in the UCHII region G045.47+0.05

¹ Instituto de Astronomía y Física del Espacio (IAFE), CC 67, Suc. 28, 1428 Buenos Aires, Argentina
e-mail: mortega@iafe.uba.ar
² FADU – Universidad de Buenos Aires, Argentina
³ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile

Received: 17 April 2012
Accepted: 2 August 2012

Abstract

Aims. 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.

Methods. We carried out observations towards a region of 2′ × 2′ centered at RA = 19^h14^m25.6^s, 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.

Results. 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 300 M_⊙. We derive a dynamical time (flow’s age) of about 10⁵ yr 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 15 M_⊙. 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.