HII region G46.5-0.2: the interplay between ionizing radiation, molecular gas and star formation

Abstract

HII regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing towards the ionizing sources, and cometary globules of dense gas, where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic HII region located at about 4 kpc, is an excellent target to perform this kind of studies. Using public molecular data extracted from the Galactic Ring Survey (13CO J=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 the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment and the young stellar objects placed around it. We found that G46, probably excited by an O7V star, is located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It presents a horse-shoe morphology opening in direction of the cloud. We observed a filamentary structure in the molecular gas likely related to G46 and not considerable molecular emission towards its open border. We found that about 10' towards the southwest of G46 there are some pillar-like features, shining at 8 um and pointing towards the HII region open border. We propose that the pillar-like features were carved and sculpted by the ionizing flux from G46. We found several young stellar objects likely embedded in the molecular cloud grouped in two main concentrations: one, closer to the G46 open border consisting of Class II type sources, and other one mostly composed by Class I type YSOs located just ahead the pillars-like features, strongly suggesting an age gradient in the YSOs distribution.

Accepted for publication in The Astronomical Journal (April 14, 2015). Some figures were degraded to reduce file size

References in corpus (13)

• A Spitzer Survey of Young Stellar Clusters within One Kiloparsec of the Sun: Cluster Core Extraction and Basic Structural Analysis
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster
• UBVJHK synthetic photometry of Galactic O stars
• Kinematic Distances to Molecular Clouds identified in the Galactic Ring Survey
• Resolution of the Distance Ambiguity for Galactic HII Regions
• Molecular gas in extreme star-forming environments: the starbursts Arp220 and NGC6240 as case studies
• A 24 Micron Point Source Catalog of the Galactic Plane from Spitzer/MIPSGAL
• Triggered massive-star formation on the borders of Galactic HII regions. IV- Star formation at the periphery of Sh2-212
• Radio Recombination Lines in Galactic HII Regions
• Molecular clouds and clumps in the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• Testing Triggered Star Formation in Six H II Regions
• Molecular excitation in the Eagle nebula's fingers

Cited by in corpus (2)

• Young Stars near Cometary Globule CG 30 in the Tumultuous Gum Nebula
• The molecular environment of the pillar-like features in the HII region G46.5-0.2