A CO Line and Infrared Continuum Study of the Active Star-Forming Complex W51

Abstract

We present the results of an extensive observational study of the active star-forming complex W51 that was observed in the J=2-1 transition of the 12CO and 13CO molecules over a 1.25 deg x 1.00 deg region with the University of Arizona Heinrich Hertz Submillimeter Telescope. We use a statistical equilibrium code to estimate physical properties of the molecular gas. We compare the molecular cloud morphology with the distribution of infrared (IR) and radio continuum sources, and find associations between molecular clouds and young stellar objects (YSOs) listed in Spitzer IR catalogs. The ratios of CO lines associated with HII regions are different from the ratios outside the active star-forming regions. We present evidence of star formation triggered by the expansion of the HII regions and by cloud-cloud collisions. We estimate that about 1% of the cloud mass is currently in YSOs.

18 pages, 29 figures; accepted for publication in ApJS

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• The molecular cloud lifecycle
• Stellar clusters in the inner Galaxy and their correlation with cold dust emission
• The Effect of Spiral Arms on Star Formation in the Galaxy
• The JCMT Plane Survey: First complete data release - emission maps and compact source catalogue
• The dense gas mass fraction in the W51 cloud and its protoclusters
• Chemical Analysis of a Diffuse Cloud along a Line of Sight Toward W51: Molecular Fraction and Cosmic-Ray Ionization Rate
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) : Molecular clouds toward W33 ; possible evidence for a cloud-cloud collision triggering O star formation
• EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions
• Extreme infrared variables from UKIDSS - II. an end-of-survey catalogue of eruptive YSOs and unusual stars
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN). VI. Dense gas and mini-starbursts in the W43 giant molecular cloud complex
• Surveying the Giant HII Regions of the Milky Way with SOFIA: I. W51A
• The molecular cloud S242: physical environment and star formation activities
• 12CO (3-2) High-Resolution Survey (COHRS) of the Galactic Plane: Complete Data Release
• Near-infrared spectroscopy of the massive stellar population of W51: evidence for multi-seeded star formation
• Detection of a dense clump in a filament interacting with W51e2
• Disentangling the radio emission of the supernova remnant W51C
• Extreme star formation in the Milky Way: Luminosity distributions of young stellar objects in W49A and W51
• Deuterium fractionation of a distant cold dark cloud along the line of sight of W51
• Submillimeter Observations of Dense Clumps in the Infrared Dark Cloud G049.40-00.01