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On the ionization of the intercloud medium by runaway O-B starsH II regions around seven high-velocity stars of type O5 to B1 (lambda Cep, xi Per, 68 Cyg, alpha Cam, AE Aur, zeta Oph, mu Col) are investigated assuming 'on-the-spot' reabsorption of the diffuse UV and time-dependent cooling and recombination behind the stars. Ratios of column densities integrated through the H II regions are obtained for stationary and moving stars, and the ionization structure is calculated for an H II region around a runaway star moving perpendicular to the galactic plane. The total volume ionized is found to be practically independent of the star's velocity. Global properties of the intercloud medium are examined; it is found that the presence of clouds may reduce the volume ionized by as much as a factor of 7 and that as much as 30% of the total ionizing radiation from early-type stars may leak out of the galaxy. Copernicus satellite observations are shown to be consistent with lines of sight crossing only the H II regions around the observed stars and a neutral intercloud medium as well as with the existence of a 'hole' in the distribution of O-B5 stars in the vicinity of the sun.
Document ID
19750051586
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Thuan, T. X.
(Princeton University New Observatory, Princeton, N.J., United States)
Date Acquired
August 8, 2013
Publication Date
June 1, 1975
Publication Information
Publication: Astrophysical Journal
Volume: 198
Subject Category
Astrophysics
Accession Number
75A35658
Funding Number(s)
CONTRACT_GRANT: NSR-31-001-901
Distribution Limits
Public
Copyright
Other

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