Enrichment of the hot intracluster medium: observations
  Four decades ago, the firm detection of an Fe-K emission feature in the X-ray
spectrum of the Perseus cluster revealed the presence of iron in its hot
intracluster medium (ICM). With more advanced missions successfully launched
over the last 20 years, this discovery has been extended to many other metals
and to the hot atmospheres of many other galaxy clusters, groups, and giant
elliptical galaxies, as evidence that the elemental bricks of life -
synthesized by stars and supernovae - are also found at the largest scales of
the Universe. Because the ICM, emitting in X-rays, is in collisional ionisation
equilibrium, its elemental abundances can in principle be accurately measured.
These abundance measurements, in turn, are valuable to constrain the physics
and environmental conditions of the Type Ia and core-collapse supernovae that
exploded and enriched the ICM over the entire cluster volume. On the other
hand, the spatial distribution of metals across the ICM constitutes a
remarkable signature of the chemical history and evolution of clusters, groups,
and ellipticals. Here, we summarise the most significant achievements in
measuring elemental abundances in the ICM, from the very first attempts up to
the era of XMM-Newton, Chandra, and Suzaku and the unprecedented results
obtained by Hitomi. We also discuss the current systematic limitations of these
measurements and how the future missions XRISM and Athena will further improve
our current knowledge of the ICM enrichment.
