On the ionization of the intercloud medium by runaway O-B stars

Abstract

view Abstract Citations (45) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the ionization of the intercloud medium by runaway O-B stars. Thuan, T. X. Abstract H 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. Publication: The Astrophysical Journal Pub Date: June 1975 DOI: 10.1086/153607 Bibcode: 1975ApJ...198..307T Keywords: Early Stars; Gas Ionization; Interstellar Matter; Stellar Motions; B Stars; Diffuse Radiation; H Ii Regions; Hydrogen Ions; O Stars; Oao 3; Photoionization; Satellite Observation; Ultraviolet Absorption; Astrophysics full text sources ADS | data products SIMBAD (9)