The classical D-type expansion of spherical H II regions
File(s)
Published version
OA Location
Author(s)
Williams, Robin JR
Bisbas, Thomas G
Haworth, Thomas J
Mackey, Jonathan
Type
Journal Article
Abstract
Recent numerical and analytic work has highlighted some shortcomings in our understanding of the dynamics of H ii region expansion, especially at late times, when the H ii region approaches pressure equilibrium with the ambient medium. Here we reconsider the idealized case of a constant radiation source in a uniform and spherically symmetric ambient medium, with an isothermal equation of state. A thick-shell solution is developed that captures the stalling of the ionization front and the decay of the leading shock to a weak compression wave as it escapes to large radii. An acoustic approximation is introduced to capture the late-time damped oscillations of the H ii region about the stagnation radius. Putting these together, a matched asymptotic equation is derived for the radius of the ionization front which accounts for both the inertia of the expanding shell and the finite temperature of the ambient medium. The solution to this equation is shown to agree very well with the numerical solution at all times, and is superior to all previously published solutions. The matched asymptotic solution can also accurately model the variation of H ii region radius for a time-varying radiation source.
Date Issued
2018-09-01
Date Acceptance
2018-05-21
Citation
Monthly Notices of the Royal Astronomical Society, 2018, 479 (2), pp.2016-2023
ISSN
0035-8711
Publisher
Oxford University Press (OUP)
Start Page
2016
End Page
2023
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
479
Issue
2
Copyright Statement
© Crown copyright 2018. This article contains public sector information licensed under the Open Government Licence v3.0 (http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/).
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000441380100039&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
ISM: bubbles
HII regions
ISM: kinematics and dynamics
STAR-FORMATION
MASSIVE STARS
IONIZING-RADIATION
TURBULENCE
EVOLUTION
CLUSTERS
ENERGY
IMPACT
WINDS
Publication Status
Published
Date Publish Online
2018-06-19