Molecule formation in quasar broad-line cloud gas

Journal Article · Thu Oct 01 04:00:00 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), Journal Name: Astrophys. J.; (United States) Vol. 321; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
COOLING
COSMIC GASES
COSMIC RADIO SOURCES
DENSITY
EMISSION SPECTRA
FLUIDS
GALAXY NUCLEI
GASES
INTERSTELLAR SPACE
LYMAN LINES
MATHEMATICAL MODELS
MOLECULES
PHYSICAL PROPERTIES
QUASARS
SPACE
SPECTRA
X-RAY SPECTRA