Study of the optical and radio absorption-line systems in AO 0235+164

Journal Article · Tue Nov 15 04:00:00 EST 1977 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/155655· OSTI ID:5235989

Wolfe, A M; Wills, B J

We investigate physical conditions in the two absorption systems present in AO 0235+164. A scan of the optical spectrum is presented. We confirm the redshift system at z=0.852, and give accurate equivalent widths for lines in the system at z=0.524. A study of the optical and 21 cm absorption spectra of the lower redshift gas shows that both types of absorption do not arise in the same line-producing region. Whereas the 21 cm features are formed in a few clouds with velocity widths ..delta..vapprox.6 km s/sup -1/, the optical lines are produced in a ''turbulent'' region with ..delta..vapprox.100 km s/sup -1/. We suggest three observational test to detect the proposed ''turbulent'' region. An analysis of the optical spectrum of the gas at z=0.852 shows that the absorbing region is characterized by ..delta nu..<20 km s/sup -1/. Excitation conditions in the z=0.524 system are deduced from the absence of UV lines arising from excited fine-structure energy levels in Fe II. The low excitation level implies that the absorber must be farther than 0.45 kpc from the continuum source, and also places upper limits on the density of the absorber as a function of its kinetic temperature and fractional ionization. These limits result in analogous restrictions on the excitation level of the hyperfine levels of H I. Thus the spin temperature of the z=0.524 system will respond to variations in the flux of the 21 cm continuum, if the absorber is located near the continuum source. At present the evidence is insufficient to locate either absorption system along the line of sight.

• Research Organization: University of Pittsburgh
• OSTI ID: 5235989
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 218:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
ATOM COLLISIONS
COLLISIONS
COSMIC RADIO SOURCES
ELECTRON COLLISIONS
ELECTRON-ION COLLISIONS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
FINE STRUCTURE
FUNCTIONS
GALAXIES
ION COLLISIONS
ION-ATOM COLLISIONS
RED SHIFT
SPECTRA
SPECTRAL FUNCTIONS