Jean M. Quashnock

An Excess of C IV Absorbers in Luminous Quasars: Evidence for Gravitational Lensing?

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 {sc iv} absorbers in bright QSOs in the redshift range

Properties of realistic cosmic-string loops

z=1.2-3.2

Effects of gravitational back reaction on small-scale structure of cosmic strings.

, and this excess increases strongly as a function of QSO absolute magnitude. No significant excess is found for Mg {sc ii} absorbers in the redshift range

Extinction and Absorption of the Afterglow of GRB980329

z=0.30-1.55

The Form and Evolution of QSO Absorption-Line System Clustering

. We rule out several possible reasons for this effect and argue that the C {sc iv} excess could be due to gravitational lensing. If so, then the lensing masses must be at

Very Large-Scale Structure Using QSO Absorption Line Systems

z gtrsim 1.5

A New Extensive Catalog of Heavy-Element QSO Absorbers: First Results

and within several hundred comoving Mpc of the QSOs, where the C {sc iv} absorbers are mainly found. The absence of an excess in the available Mg {sc ii} sample would then arise because the Mg {sc ii} data does not sample this region of space.