The relative impact of baryons and cluster shape on weak lensing mass estimates of galaxy clusters

TL;DR

This study uses hydrodynamic simulations to assess how baryonic physics and cluster shape influence weak lensing mass estimates, finding minimal bias for massive clusters but significant challenges for lower-mass systems.

Contribution

It provides a detailed analysis of baryonic effects on weak lensing mass bias and scatter using the cosmo-OWLS simulations, highlighting the importance of feedback processes and cluster shape.

Findings

Mass bias is about -10% for low-mass clusters.

No significant bias difference between dark matter-only and baryonic runs.

Scatter is mainly due to cluster triaxiality, not baryonic physics.

Abstract

Weak gravitational lensing depends on the integrated mass along the line of sight. Baryons contribute to the mass distribution of galaxy clusters and the resulting mass estimates from lensing analysis. We use the cosmo-OWLS suite of hydrodynamic simulations to investigate the impact of baryonic processes on the bias and scatter of weak lensing mass estimates of clusters. These estimates are obtained by fitting NFW profiles to mock data using MCMC techniques. In particular, we examine the difference in estimates between dark matter-only runs and those including various prescriptions for baryonic physics. We find no significant difference in the mass bias when baryonic physics is included, though the overall mass estimates are suppressed when feedback from AGN is included. For lowest-mass systems for which a reliable mass can be obtained ($M_{200} \approx 2 \times 10^{14}$ $M_{\odot}$), we find a bias of $\approx -10$ per cent. The magnitude of the bias tends to decrease for higher mass clusters, consistent with no bias for the most massive clusters which have masses comparable to those found in the CLASH and HFF samples. For the lowest mass clusters, the mass bias is particularly sensitive to the fit radii and the limits placed on the concentration prior, rendering reliable mass estimates difficult. The scatter in mass estimates between the dark matter-only and the various baryonic runs is less than between different projections of individual clusters, highlighting the importance of triaxiality.