The dark matter of gravitational lensing

TL;DR

This paper reviews how gravitational lensing has advanced our understanding of dark matter, revealing its dominant presence in the universe and constraining its properties through observational effects on light.

Contribution

It synthesizes recent progress in dark matter research via gravitational lensing, highlighting new constraints on dark matter density, particle size, and interaction cross sections.

Findings

Dark matter constitutes five-sixths of the universe's material content.

Gravitational lensing effectively constrains dark matter properties.

Observations limit dark matter particle size and interaction cross sections.

Abstract

We review progress in understanding dark matter by astrophysics, and particularly via the effect of gravitational lensing. Evidence from many different directions now all imply that five sixths of the material content of the universe is in this mysterious form, separate from and beyond the ordinary "baryonic" particles in the standard model of particle physics. Dark matter appears not to interact via the electromagnetic force, and therefore neither emits nor reflects light. However, it definitely does interact via gravity, and has played the most important role in shaping the Universe on large scales. The most successful technique with which to investigate it has so far been the effect of gravitational lensing. The curvature of space-time near any gravitating mass (including dark matter) deflects passing rays of light - observably shifting, distorting and magnifying the images of background galaxies. Measurements of such effects currently provide constraints on the mean density of dark matter, and its density relative to baryonic matter; the size and mass of individual dark matter particles; and its cross section under various fundamental forces.