Detection of anti-correlation of hot and cold baryons in galaxy clusters
  The largest clusters of galaxies in the Universe contain vast amounts of dark
matter, plus baryonic matter in two principal phases, a majority hot gas
component and a minority cold stellar phase comprising stars, compact objects,
and low-temperature gas. Hydrodynamic simulations indicate that the
highest-mass systems retain the cosmic fraction of baryons, a natural
consequence of which is anti-correlation between the masses of hot gas and
stars within dark matter halos of fixed total mass. We report observational
detection of this anti-correlation based on 4 elements of a $9\times9$ element
covariance matrix for nine cluster properties, measured from X-ray, optical,
infrared and millimetre wavelength observations of 41 clusters from the Local
Cluster Substructure Survey. These clusters were selected using explicit and
quantitative selection rules that were then encoded in our hierarchical
Bayesian model. Our detection of anti-correlation is consistent with
predictions from contemporary hydrodynamic cosmological simulations that were
not tuned to reproduce this signal.
