Dark haloes as seen with gravitational lensing
  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.
