Galaxy density profiles and shapes -- II. selection biases in strong lensing surveys

TL;DR

This study investigates how various galaxy properties and observational biases influence the selection of strong gravitational lensing systems, revealing significant biases related to mass, shape, and dark matter profiles that affect survey interpretations.

Contribution

It provides a detailed analysis of selection biases in strong lensing surveys, incorporating galaxy shape, mass, and dark matter profile variations to better understand their impact.

Findings

Mass and orientation significantly bias lensing selection.

Dark matter profile parameters affect lensing cross-section.

Galaxy shape has minimal impact when averaged over viewing angles.

Abstract

[Abridged] Many current and future astronomical surveys will rely on samples of strong gravitational lens systems to draw conclusions about galaxy mass distributions. We use a new strong lensing pipeline (presented in Paper I of this series) to explore selection biases that may cause the population of strong lensing systems to differ from the general galaxy population. Our focus is on point-source lensing by early-type galaxies with two mass components (stellar and dark matter) that have a variety of density profiles and shapes motivated by observational and theoretical studies of galaxy properties. We seek not only to quantify but also to understand the physics behind selection biases related to: galaxy mass, orientation and shape; dark matter profile parameters such as inner slope and concentration; and adiabatic contraction. We study how all of these properties affect the lensing Einstein radius, total cross-section, quad/double ratio, and image separation distribution. We find significant (factors of several) selection biases with mass; orientation, for a given galaxy shape at fixed mass; cusped dark matter profile inner slope and concentration; concentration of the stellar and dark matter deprojected Sersic models. Interestingly, the intrinsic shape of a galaxy does not strongly influence its lensing cross-section when we average over viewing angles. Our results are an important first step towards understanding how strong lens systems relate to the general galaxy population.