Weak Lensing–X-ray Scaling Relations for a High Redshift Galaxy Clusters Sample

Abstract

Accurate cosmology through large X-ray selected galaxy cluster samples will rely on accurate mass estimates and well-calibrated mass-observable relations. The comparison of independent approaches, such as X-ray and gravitational lensing analysis, yields the most accurate results in tracing the cosmic evolution. This also contributes to improve our understanding of the scaling laws between X-ray luminosity and mass, providing the essential connection between observations and cosmological constraints that will be obtained thanks to the forthcoming eROSITA X-ray space telescope.<br /> Our project aims at the mass estimation via the weak lensing follow-up of the cosmological subsample of the 400d Galaxy Cluster Survey: a homogeneous, statistically complete and flux limited X-ray sample of 36 high-redshift (0.35 ≤ z < 0.90) clusters, covering an as yet unexplored region in the mass-redshift parameter space.<br /> After a brief introduction about cluster cosmology, this thesis presents methods and results of the cluster mass estimation through an homogeneous weak lensing analysis of 18 galaxy clusters.<br /> For our purposes we use optical data from archival and granted observations at ground-based instruments: IMACS, WFI and MegaCam wide-field cameras. Given the poor quality of the data format of the IMACS camera, we modify and automatize the THELI data reduction pipeline and implement a method for recovering precious astrometric information.<br /> We provide revised scaling relations of weak lensing mass with several X-ray observables integrating the new data with updated masses from the previous works, basing on a total of 25 high-z clusters. We compare our results with the X-ray mass estimates and recent mass comparison projects.<br /> We find a hint for a mass-dependent mass bias, with X-ray mass estimates of low-mass clusters (w.r.t. the sample median mass) being biased-high, while they are biased-low at the high-mass end. However, the overall trend is consistent with the zero bias, hence not showing any indication for a strong cluster mass bias which would be needed to alleviate the Planck CMB-cluster tension.