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Evolution of prolate molecular clouds at HII boundaries - II. Formation of BRCs of asymmetrical morphology

Kinnear, T.M., Miao, Jingqi, White, G.J., Sugitani, K., Goodwin, S. (2015) Evolution of prolate molecular clouds at HII boundaries - II. Formation of BRCs of asymmetrical morphology. Monthly Notices of the Royal Astronomical Society, 450 (1). pp. 1017-1031. ISSN 0035-8711. (doi:10.1093/mnras/stv637) (KAR id:50014)

Language: English
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A systematic investigation on the evolution of a prolate cloud at an H II boundary is conducted using smoothed particle hydrodynamics in order to understand the mechanism for a variety of irregular morphological structures found at the boundaries of various H II regions. The prolate molecular clouds in this investigation are set with their semimajor axes at inclinations between 0° and 90° to a plane-parallel ionizing radiation flux. A set of four parameters, the number density n, the ratio of major to minor axis ?, the inclination angle ? and the incident flux FEUV, are used to define the initial state of the simulated clouds. The dependence of the evolution of a prolate cloud under radiation-driven implosion (RDI) on each of the four parameters is investigated. It is found that (i) in addition to the well-studied standard type A, B or C bright-rimmed clouds (BRCs), many other types such as asymmetrical BRCs, filamentary structures and irregular horse-head structures could also be developed at H II boundaries with only simple initial conditions; (ii) the final morphological structures are very sensitive to the four initial parameters, especially to the initial density and the inclination; (iii) the previously defined ionizing radiation penetration depth can still be used as a good indicator of the final morphology. Based on the simulation results, the formation time-scales and masses of the early RDI-triggered star formation from clouds of different initial conditions are also estimated. Finally a unified mechanism for the various morphological structures found in many different H II boundaries is suggested.

Item Type: Article
DOI/Identification number: 10.1093/mnras/stv637
Uncontrolled keywords: H II regions, Hydrodynamics, ISM: evolution, ISM: kinematics and dynamics, Radiative transfer, Stars: formation
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: J. Miao
Date Deposited: 04 Aug 2015 14:49 UTC
Last Modified: 29 May 2019 15:53 UTC
Resource URI: (The current URI for this page, for reference purposes)
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