X-ray photoionized nebulae

Journal Article · Mon Dec 15 04:00:00 EST 1980 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/158535· OSTI ID:6536638

Halpern, J P; Grindlay, J E

A galactic X-ray source within a dense interstellar cloud will excite a compact H II region as well as a larger sphere of partial ionization. We have calculated the equilibrium ionization and thermal balance in a uniform-density cloud which is optically thin to a point source of X-rays for several bremsstrahlung spectra. The elements included are hydrogen, helium, carbon, nitrogen, oxygen, and neon. Charge-transfer reactions, Auger emission, and ionization by energetic photoelectrons are important in determining the structure of the gas. Compton heating and ionization by incoherent Compton scattering can be significant for extremely hard spectra. The integrated optical emission from these nebulae show several features which readily distinguish them from stellar induced H II regions. The radiation from the partially ionized gas is dominated by forbidden lines of neutral and singly ionized species, with a smaller contribution from hydrogen continuum and Balmer lines. O III is severely depleted by charge transfer, and (O I) l6300 can be stronger than (O II)l3727. X-ray photoionization may help to explain properties of a wide variety of galactic and extragalactic objects.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 6536638
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 242:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATOMIC MODELS
AUGER EFFECT
BASIC INTERACTIONS
CHARGE EXCHANGE
CHEMICAL REACTIONS
COMPTON EFFECT
COOLING
COSMIC RADIO SOURCES
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
CROSS SECTIONS
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELECTRON EMISSION
EMISSION
H2 REGIONS
HEATING
INTERACTIONS
IONIZATION
MATHEMATICAL MODELS
NEBULAE
OPTICAL PROPERTIES
PHOTOIONIZATION
PHYSICAL PROPERTIES
RADIATION TRANSPORT
SCATTERING