Mass models of galaxy clusters from a non-parametric weak-lensing reconstruction

TL;DR

This paper introduces a non-parametric weak-lensing method to derive galaxy cluster mass profiles, revealing insights into baryonic fractions and their relation to galaxy scaling laws, with results consistent with ΛCDM predictions.

Contribution

The study presents a novel non-parametric deprojection technique for weak lensing data, enabling mass profile inference without assuming specific halo models, and applies it to the CLASH cluster sample.

Findings

Circular velocities are approximately flat at large radii.

Radially resolved baryonic mass fractions vary significantly among clusters.

Mass profiles are consistent with the stellar mass--halo mass relation in ΛCDM.

Abstract

We study the CLASH sample of galaxy clusters using a new deprojection method for weak gravitational lensing observations. This method is non-parametric, allowing us to infer mass profiles, or equivalently circular velocities, without having to assume a specific halo profile. While this method assumes spherical symmetry, we show that, on average, triaxiality is unlikely to significantly affect our results. We use this method to study the total mass profiles of the CLASH clusters, as well as the relation between their total and baryonic components: (1) We find that the implied circular velocities are consistent with being approximately flat at large radii, akin to the rotation curves of galaxies. (2) We infer radially resolved baryonic mass fractions, finding that these vary significantly from cluster to cluster and depend strongly on the details of the X-ray gas mass profiles. Since the gas mass profiles are poorly constrained at large radii, it is unclear whether the CLASH clusters reach the cosmic baryon fraction expected in $\Lambda$CDM. (3) The non-parametric masses are consistent with the stellar mass--halo mass relation expected in $\Lambda$CDM. (4) Galaxy clusters systematically deviate from the Baryonic Tully-Fisher Relation (BTFR) and the Radial Acceleration Relation (RAR) defined by galaxies, but the magnitude of the offset depends strongly on the gas mass extrapolation at large radii. Contrary to some previous results based on hydrostatic equilibrium, we find that galaxy clusters may fall on the same BTFR and RAR as galaxies if one adds a suitable positive baryonic mass component.