Model-Free Multi-Probe Lensing Reconstruction of Cluster Mass Profiles

TL;DR

This paper introduces a multi-probe, model-free Bayesian method for reconstructing galaxy cluster mass profiles by combining magnification bias and lens distortion measurements, enhancing accuracy and breaking degeneracies.

Contribution

It generalizes previous Bayesian approaches to incorporate multiple background source populations and combines weak and strong lensing data for non-parametric mass profiling.

Findings

Improved mass profile reconstruction for MACS J1206.2-0847.

Enhanced statistical precision by combining multi-probe lensing data.

Potential for stacked lensing analyses to determine average mass profiles.

Abstract

Lens magnification by galaxy clusters induces characteristic spatial variations in the number counts of background sources, amplifying their observed fluxes and expanding the area of sky, the net effect of which, known as magnification bias, depends on the intrinsic faint-end slope of the source luminosity function. The bias is strongly negative for red galaxies, dominated by the geometric area distortion, whereas it is mildly positive for blue galaxies, enhancing the blue counts toward the cluster center. We generalize the Bayesian approach of Umetsu et al. for reconstructing projected cluster mass profiles, by incorporating multiple populations of background sources for magnification bias measurements and combining them with complementary lens distortion measurements, effectively breaking the mass-sheet degeneracy and improving the statistical precision of cluster mass measurements. The approach can be further extended to include strong-lensing projected mass estimates, thus allowing for non-parametric absolute mass determinations in both the weak and strong regimes. We apply this method to our recent CLASH lensing measurements of MACS J1206.2-0847, and demonstrate how combining multi-probe lensing constraints can improve the reconstruction of cluster mass profiles. This method will also be useful for a stacked lensing analysis, combining all lensing-related effects in the cluster regime, for a definitive determination of the averaged mass profile.