Abstract:

Accurate reconstruction of galaxy cluster mass profiles beyond the virial radius is vital for testing non-equilibrium halo assembly, dark matter physics, and modified gravity. In this talk, we present Λ-CLUMI+, a minimally model-dependent, data-driven, multi-probe framework that reconstructs the mass distribution in and around galaxy clusters by combining weak lensing (shear and magnification) and dynamical (escape velocity) observations. Λ-CLUMI+ is an extension of the original CLUMI+ methodology, which models escape velocity within a standard Newtonian framework. Λ-CLUMI+ now incorporates the effects of accelerated cosmic expansion into the modeling of the escape velocity profile.

Using a statistical sample of synthetic lensing and phase-space observations from the IllustrisTNG-300 simulation, we show that both approaches yield unbiased mass profile reconstructions up to ∼10 Mpc. Crucially, accounting for cosmic acceleration mitigates systematic modeling errors and improves the accuracy of the reconstruction within the cluster infall region. Furthermore, we demonstrate that the Λ-CLUMI+ methodology provides robust mass reconstructions even in the absence of magnification data, establishing a powerful baseline for cosmological applications in the era of wide-field imaging and spectroscopic surveys such as DESI, Euclid, and the Nancy Grace Roman Space Telescope.