High-Resolution Observations of the Molecular Clouds Associated with the Huge HII Region CTB 102

Abstract

We report the first high-resolution (sub-arcminute) large-scale mapping ${}^{12}$CO and ${}^{13}$CO observations of the molecular clouds associated with the giant outer Galaxy HII region CTB~102 (KR 1). These observations were made using a newly commissioned receiver system on the 13.7-m radio telescope at the Taeduk Radio Astronomy Observatory. Our observations show that the molecular clouds have a spatial extent of $60\times 35$ pc and a total mass of $10^{4.8}-10^{5.0}$ M${}_{\odot }$. Infrared data from WISE and 2MASS were used to identify and classify the YSO population associated with ongoing star formation activity within the molecular clouds. We directly detect 18 class I/class II YSOs and six transition disk objects. Moving away from the HII region, there is an age/class gradient consistent with sequential star formation. The infrared and molecular-line data were combined to estimate the star formation efficiency (SFE) of the entire cloud as well as the SFE for various sub-regions of the cloud. We find that the overall SFE is between $\sim 5-10$%, consistent with previous observations of giant molecular clouds. One of the sub-regions, region 1a, is a clear outlier, with a SFE of 17 $-$ 35% on a 5 pc spatial scale. This high SFE is more typical for much smaller (sub-pc scale) star-forming cores, and we think region 1a is likely an embedded massive protocluster.

arXiv comment16 pages, 8 figures, 5 tables

References in corpus (14)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• Embedded Clusters in Molecular Clouds
• The CO-to-H2 Conversion Factor
• The Spitzer c2d Legacy Results: Star Formation Rates and Efficiencies; Evolution and Lifetimes
• Interpreting Spectral Energy Distributions from Young Stellar Objects. II. Fitting observed SEDs using a large grid of pre-computed models
• Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A grid of 200,000 YSO model SEDs
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• HII Region Metallicity Distribution in the Milky Way Disk
• A Classification Scheme for Young Stellar Objects Using the WIDE-FIELD INFRARED SURVEY EXPLORER AllWISE Catalog: Revealing Low-Density Star Formation in the Outer Galaxy
• The X_CO conversion factor from galactic multiphase ISM simulations
• Does the CO-to-H2 conversion factor depend on the star formation rate?
• How well does CO emission measure the H${}_2$ mass of MCs?
• The Interstellar Bubbles of G38.9-0.4 and the Impact of Stellar Feedback on Star Formation
• The enormous outer Galaxy HII region CTB 102

Cited by in corpus (1)

• BFS 10: A nascent bipolar H II region in a filamentary molecular cloud