Large-Scale Kinematics, Astrochemistry and Magnetic Field Studies of Massive Star-forming Regions through HC3N, HNC and C2H Mappings

Abstract

We have mapped 27 massive star-forming regions associated with water masers using three dense gas tracers: HC3N 10-9, HNC 1-0 and C2H 1-0. The FWHM sizes of HNC clumps and C2H clumps are about 1.5 and 1.6 times higher than those of HC3N, respectively, which can be explained by the fact that HC3N traces more dense gas than HNC and C2H. We found evidence for increase in optical depth of C2H with `radius' from center to outer regions in some targets, supporting the chemical model of C2H. The C2H optical depth is found to decline as molecular clouds evolve to later stage, suggesting that C2H might be used as "chemical clock" for molecular clouds. Large-scale kinematic structure of clouds was investigated with three molecular lines. All these sources show significant velocity gradients. The magnitudes of gradient are found to increase towards the inner region, indicating differential rotation of clouds. Both the ratio of rotational to gravitational energy and specific angular momentum seem to decrease toward the inner region, implying obvious angular momentum transfer, which might be caused by magnetic braking. The average magnetic field strength and number density of molecular clouds is derived using the uniformly magnetic sphere model. The derived magnetic field strengths range from 3 to 88 μG, with a median value of 13 μG. The mass-to-flux ratio of molecular cloud is calculated to be much higher than critical value with derived parameters, which agrees well with numerical simulations.

56 pages, 24 figures, accepted by ApJ

References in corpus (9)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• Cold Dark Clouds: The Initial Conditions for Star Formation
• Molecular Cloud Evolution IV: Magnetic Fields, Ambipolar Diffusion, and the Star Formation Efficiency
• Ethynyl (C2H) in massive star formation: Tracing the initial conditions?
• Radio Recombination Lines in Galactic HII Regions
• Angular Momentum in Giant Molecular Clouds. I. The Milky Way
• The Decrease of Specific Angular Momentum and the Hot Toroid Formation: The Massive Clump G10.6-0.4
• A multi-transition molecular line study of inward motions towards massive star-forming cores
• Early phase of massive star formation: A case study of Infrared dark cloud G084.81-01.09

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