H II Region G46.5-0.2: The Interplay between Ionizing Radiation, Molecular Gas, and Star Formation

S. PARON; M. E. ORTEGA; G. DUBNER; J. YUAN; A. PETRIELLA; E. GIACANI; J. LI; Y. WU; H. LIU; Y. HUANG; S. ZHANG

ASTRONOMICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2015 vol. 149

0004-6256

HII regions are particularly interesting because they can generatedense layers of gas and dust, elongated columns or pillars of gaspointing toward the ionizing sources, and cometary globules of dense gaswhere triggered star formation can occur. Understanding the interplaybetween the ionizing radiation and the dense surrounding gas is veryimportant to explain the origin of these peculiar structures, and henceto characterize triggered star formation. G46.5-0.2 (G46), a poorlystudied galactic HII region located at about 4 kpc, is an excellenttarget for performing this kind of study. Using public molecular dataextracted from the Galactic Ring Survey (13COJ=1-0)and from the James Clerk Maxwell Telescope data archive(12CO, 13CO, C18O J=3-2,HCO+, and HCN J=4-3), and infrared data from theGLIMPSE and MIPSGAL surveys, we perform a complete study of G46, itsmolecular environment, and the young stellar objects (YSOs) placedaround it. We found that G46, probably excited by an O7V star, islocated close to the edge of the GRSMC G046.34-00.21 molecular cloud. Itpresents a horse-shoe morphology opening in the direction of the cloud.We observed a filamentary structure in the molecular gas likely relatedto G46 and not considerable molecular emission toward its open border.We found that about 10‧ to the southwest of G46 there are somepillar-like features, shining at 8 microns and pointing toward the HII region open border. We propose that the pillar-like features were carvedand sculpted by the ionizing flux from G46. We found several YSOs likelyembedded in the molecular cloud grouped in two main concentrations: one,closer to the G46 open border consisting of Class II type sources, andanother mostly composed of Class I type YSOs located just ahead of thepillar-like features, strongly suggesting an age gradient in the YSOdistribution.