We have compiled a new and extensive catalog of heavy-element QSO absorption-line systems and analyzed the distribution of absorbers in bright and faint QSOs, to search for gravitational lensing of background QSOs by the matter associated with the absorbers. There is a highly significant excess of C IV absorbers in bright QSOs in the redshift range z = 1.2-3.2, and this excess increases strongly as a function of QSO absolute magnitude. No significant excess is found for Mg II absorbers in the redshift range z = 0.30-1.55. We rule out several possible reasons for this effect and argue that the C IV excess could be due to gravitational lensing. If so, then the lensing masses must be at z >~ 1.5 and within several hundred comoving megaparsecs of the QSOs, where the C IV absorbers are mainly found. The absence of an excess in the available Mg II sample would then arise because the Mg II data do not sample this region of space.
The Astrophysical Journal
- Pub Date:
- September 1996
- COSMOLOGY: GRAVITATIONAL LENSING;
- GALAXIES: QUASARS: ABSORPTION LINES;
- 21 LaTeX pages with 5 encapsulated Postscript figures included, uses AASTeX (v. 4.0) available at ftp://ftp.aas.org/pubs/ , to appear in The Astrophysical Journal, Sept. 20, 1996