Cosmological large scale structure (LSS) evolved from quantum fluctuations in the primordial matter-density field. Since this evolution is dominated by gravitational dynamics, LSS exhibits significant memory of these initial conditions. This makes such LSS sensitive to the properties of the primordial matter-density field and cosmology in general. The central challenge to using LSS to constrain cosmology is modeling the connection between observed tracers of this structure and the underlying dark matter, its primary constituent.
Two of the most commonly used tracers of LSS are galaxies and galaxy clusters. Clusters are embedded in the universe's largest dark matter halos. These halos formed from the largest and rarest peaks in the primordial matter-density field and are extremely sensitive to cosmology, in particular the amplitude of initial fluctuations and matter density. Galaxies are less sensitive to cosmology than clusters but are nonetheless important LSS tracers by virtue of their abundance.
Typically the abundance of galaxy clusters as a function of mass is used to constrain cosmology. However, large-scale cluster-mass correlations probed by weak gravitational lensing are a novel and promising alternative method. Both approaches rely critically the ability to accurately characterize and calibrate the cluster-mass observable relation. We advocate the latter approach, combining the stacked lensing profiles of clusters selected by optical richness with the cross-correlation of said clusters with galaxies and the auto-correlation of galaxies. We show that this novel combination of observables can yield simultaneous tight constraints on both cosmology and the cluster-mass observable relation.
