Quadruply-imaged quasars: some general features

TL;DR

This paper investigates the relationship between the configuration of four images produced by gravitational lensing of quasars and the source position, revealing correlations and biases in observed data that enhance understanding of lensing mechanisms.

Contribution

It provides an analysis of quadruply-imaged quasars, highlighting correlations between image configurations and source positions, and discusses biases in observed samples.

Findings

Strong correlations between image configuration parameters.

Evidence of bias towards large magnification systems.

Insights into the gravitational lensing mechanism.

Abstract

Gravitational lensing of point sources located inside the lens caustic is known to produce four images in a configuration closely related to the source position. We study this relation in the particular case of a sample of quadruply-imaged quasars observed by the Hubble Space Telescope (HST). Strong correlations between the parameters defining the image configuration are revealed. The relation between the image configuration and the source position is studied. Some simple features of the selected data sample are exposed and commented upon. In particular, evidence is found for the selected sample to be biased in favour of large magnification systems. While having no direct impact on practical analyses of specific systems, the results have pedagogical value and deepen our understanding of the mechanism of gravitational lensing.