Study of the molecular and ionized gas in a precursor of an ultra-compact HII region

MÓNICA RUBIO; SERGIO PARON; MÓNICA RUBIO; SERGIO PARON; ALBERTO PETRIELLA; ELSA GIACANI; ALBERTO PETRIELLA; ELSA GIACANI; MARIELA CELIS PEÑA; MARTIN ORTEGA; MARIELA CELIS PEÑA; MARTIN ORTEGA

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2017

0004-6361

Aims. We study the molecular and the ionized gas in a precursor of an ultra-compact H ii region to contribute to the understanding ofhow high-mass stars build-up their masses once they have reached the zero-age main secuence.Methods. We carried out molecular observation towards the position of the Red MSX source G052.9221−00.4892, using the AtacamaSubmillimeter Telescope Experiment (ASTE; Chile) in the 12 CO J=3−2, 13 CO J=3−2, C 18 O J=3−2, and HCO + J=4−3 lines with anangular resolution of about 22 ′′ . We also present radio continuum observations at 6 GHz carried out with the Jansky Very Large Array(JVLA; EEUU) interferometer with a synthesized beam of 4 ′′ . 8 × 4 ′′ . 1. The molecular data was used to study the distribution andkinematics of the molecular gas, while the radio continuum data was used to characterize the ionized gas in the region. Combiningthese observations with infrared public data allowed us to build up a comprehensive picture of the nature of the source.Results. The analysis of the molecular observations reveals the presence of a kinetic temperature and H 2 column density gradientsacross the molecular clump in which the Red MSX source G052.9221−00.4892 is embedded, with the hotter and less dense gas in theinner region. The 12 CO J=3−2 emission shows evidence of misaligned massive molecular outflows, with the blue lobe in positionalcoincidence with a jet-like feature seen at 8 μm. The radio continuum emission shows an elongated compact radio source, with aflux density of about 0.9 mJy, in positional coincidence with the Red MSX source. The polar-like morphology of this compact radiosource perfectly matches the hourglass-like morphology exhibited by the source in the K s −band. Moreover, the axes of symmetry ofthe radio source and the near-infrared nebula are perfectly aligned. Thus, based on these results together with the lack of evidence ofjets, we suggest that the Red MSX source G052.9221−00.4892 is transiting the hyper-compact H ii region phase, in which the youngcentral star emits winds and ionizing radiation through the poles.