Molecule formation in quasar broad-line cloud gas

Journal Article · Thu Oct 01 00:00:00 EDT 1987 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/165683· OSTI ID:5671840

Kallman, T; Lepp, S; Giovannoni, P

Models for the broad-line emitting clouds of quasars typically assume that the clouds have column densities of at most 10 to the 23rd/sq cm. The consequences of relaxing this assumption are examined, and it is shown that: (1) at slightly larger column densities the gas may cool to about 1000 K as a result of molecule formation; (2) in much of the molecule-forming region the temperature may have either of two values, about 1000 K or 6000-8000 K; (3) the strengths of most observable optical lines, including C II semiforbidden 2326-A lines and Fe II lines, are unaffected by such large column densities; and (4) lines from low-ionization species such as Na I are readily formed at large column densities. Observations of such lines provide evidence for large cloud column densities. 47 references.

• Research Organization: NASA, Goddard Space Flight Center, Greenbelt, MD; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; Maryland Univ., College Park
• OSTI ID: 5671840
• Journal Information: Astrophys. J.; (United States), Vol. 321
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
QUASARS
COSMIC GASES
ABUNDANCE
COOLING
DENSITY
EMISSION SPECTRA
GALAXY NUCLEI
INTERSTELLAR SPACE
LYMAN LINES
MATHEMATICAL MODELS
MOLECULES
X-RAY SPECTRA
COSMIC RADIO SOURCES
FLUIDS
GASES
PHYSICAL PROPERTIES
SPACE
SPECTRA
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Radio & X-Ray Sources