Dark haloes as seen with gravitational lensing

TL;DR

This paper reviews how gravitational lensing, especially weak lensing, is used to study dark matter halos around galaxies, highlighting the KiDS survey's role in measuring halo properties across different environments and redshifts.

Contribution

It introduces the KiDS survey and its application in analyzing galaxy halo masses, shapes, and extents through weak lensing observations.

Findings

KiDS survey enables detailed measurements of galaxy halo properties.

Weak lensing effectively probes dark matter halos out to hundreds of kiloparsecs.

The study advances understanding of dark matter distribution around galaxies.

Abstract

Dark matter is an important ingredient of galaxies, as was recognised early on by Ken Freeman himself! Evidence for dark matter halos is still indirect, based on analysing motions of tracers such as gas and stars. In a sense the visible galaxy is the mask through which we can study the dark matter. Light rays are also sensitive to gravitational fields, and dark haloes cause observable gravitational lensing effects. There are three regimes: microlensing (which probes the clumpiness of dark matter haloes), strong lensing (sensitive to the inner mass distribution) and weak lensing (which can probe haloes out to 100s of kpc from the center). This review will concentrate on weak lensing, and describe a new survey, the Kilo-Degree Survey (KiDS) that is designed to study galaxy halo masses, extents and shapes as a function of environment, galaxy type and redshift.