The ionization of a low-density intercloud medium by a single O star

Journal Article · Wed Sep 01 04:00:00 EDT 1976 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/190395· OSTI ID:7250812

Elmegreen, B G

The O-star ionization of hydrogen in a cloud-containing, low-density (< or =0.2 cm/sup -3/) medium is considered with special regard for the radiative transfer of diffuse recombination radiation. We thereby determine the extent of ionization by diffuse light in the regions which are obscured from the direct stellar radiation by neutral clouds. Recombination of hydrogen on exposed cloud surfaces and in the intercloud medium are treated as separate sources of Lyman continuum radiation. Neutral clouds are assumed to exist only beyond a ''destruction'' distance from the star, and there the surfaces are assumed to be random in orientation and location.The results of a numerical integration of the equations of radiative transfer in the H II region indicate that the hydrogen in cloud shadows may be completely ionized by diffuse light within approximately half of the Stromgren radius, depending slightly upon that Stromgren radius, the average frequency of Lyman continuum radiation from the star, and the average cloud size. The expected emission measure from such a cloud-containing H II region is also calculated and shown to compare well with that obtained from the observation of H..cap alpha.. emission around runaway O stars, suggesting that much of the Lyman continuum radiation from these stars may be absorbed on the surfaces of neutral clouds. (AIP)

• Research Organization: Princeton University Observatory
• OSTI ID: 7250812
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 32:1; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RADIO SOURCES
COSMOLOGICAL MODELS
H2 REGIONS
INTERSTELLAR SPACE
IONIZATION
LYMAN LINES
MATHEMATICAL MODELS
RADIATION TRANSPORT
SPACE
STARS