Evolution of HII regions in hierarchically structured molecular clouds

Abstract

We present observations of the H91$\alpha$ recombination line emission towards a sample of nine HII regions associated with 6.7-GHz methanol masers, and report arcsecond-scale emission around compact cores. We derive physical parameters for our sources, and find that although simple hydrostatic models of region evolution reproduce the observed region sizes, they significantly underestimate emission measures. We argue that these findings are consistent with young source ages in our sample, and can be explained by existence of density gradients in the ionised gas.

11 pages, 6 figures; accepted for publication in MNRAS

References in corpus (14)

• Physical Conditions in Regions of Star Formation
• High-Mass Proto-Stellar Candidates - II : Density structure from dust continuum and CS emission
• Massive Stars: Their Environment and Formation
• Structure and Evolution of the Envelopes of Deeply Embedded Massive Young Stars
• The Formation of Massive Stars by Accretion Through Trapped Hypercompact HII Regions
• Radio Continuum and Recombination Line Study of UC HII Regions with Extended Envelopes
• Clumpy Ultracompact HII Regions I: Fully Supersonic Wind-blown Models
• Continuum emission associated with 6.7-GHz methanol masers
• Extended emission associated with young HII regions
• Molecular Counterparts of Ultracompact HII Regions with Extended Envelopes
• A search for 85.5- and 86.6-GHz methanol maser emission
• Interaction between Ionized and Molecular Gas in the Active Star-Forming Region W31
• High-Resolution Mid-Infrared Imaging of G339.88-1.26
• Initial Ionization of Compressible Turbulence

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