Unifying cluster and galaxy cosmology analyses using the galaxy-halo connection

Abstract

Galaxies and galaxy clusters trace the same cosmic density field, but their statistics have been modeled separately in cosmological analyses. We present a unified, simulation-based framework to model them using the galaxy-halo connection. Our analysis includes cluster lensing, galaxy clustering, and galaxy-cluster cross-correlation. We validate our method on the FLAMINGO hydrodynamic simulation. Relative to the cluster-only approach, combining these probes improves the $σ_8-Ω_m$ figure of merit by a factor of 15. Our framework enables stringent tests of cosmological models and exploits small-scale information.

Figures (2)

• Figure 1: Validation of our unified framework. The points with error bars correspond to the mock observations from flamingo, and the four panels correspond to cluster lensing (CL), galaxy density and clustering (GG), cluster-galaxy cross-correlation (C$\times$G), and galaxy-galaxy lensing (GGL). We fit our models to the first three (excluding GGL due to uncertainties in baryonic physics), and the bands correspond to the posterior predictions. Our model describes all these data vectors well and leads to unbiased, competitive cosmological constraints (see Fig. \ref{['fig:mcmc']}).
• Figure 2: Forecasted constraints derived from fitting the unified model to simulated data vector combinations. With the unified framework, adding galaxy clustering (GG) significantly improves the constraints from cluster lensing alone (CL). Adding cluster-galaxy cross correlation (C$\times$G) further tightens the constraints (also see Table \ref{['tab:FoM']}). We assume a survey volume matching the flamingo simulation, 1 Gpc$^3$.