Statistics – Computation
Scientific paper
Aug 1990
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990a%26a...235....8b&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 235, no. 1-2, Aug. 1990, p. 8-14.
Statistics
Computation
12
Absorption Spectra, Galactic Evolution, Quasars, Red Shift, Ultraviolet Radiation, Astronomical Models, Background Radiation, Computational Astrophysics, Diffuse Radiation, Spectral Line Width
Scientific paper
The cosmological evolution of metal-rich absorption-line systems in the spectra of QSOs are investigated theoretically. The observational data of Sargent et al. (1988) are analyzed statistically; a new type of evolution involving the rest-equivalent-width line ratio of Si IV (1393 A) to C IV (1548 A) is described; and simple absorber models for gaseous galactic halos are developed in which the redshift evolutions of density and metal content in the absorbing gas and the diffuse UV background (DUB) are constrained by the observed evolutions. It is found that, as z increases from 1.5 to 3.2, the absorber metal content decreases and the density increases, suggesting expansion of the outer parts of galactic halos. No evidence of evolution is found in Lyman-limit systems or in the DUB.
Bergeron Jacqueline
Ikeuchi Satoru
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