A major galaxy cluster merger caught by eROSITA: weak lensing mass distribution and kinematic description

Abstract

We present the weak lensing mass distribution of a triple merging cluster candidate at $z_{\rm photo}\sim 0.36$ belonging to a supercluster recently discovered during the eROSITA Performance Verification phase. Our analysis solved a previous tension in the merger classification by confirming that the cluster pair eFEDS J093513.3+004746 and eFEDS J093510.7+004910 is undergoing a major merger with a mass ratio $1.7_{-0.7}^{+0.5}$. According to our two-body kinematic description, the encounter happened $0.58_{-0.20}^{+0.15}$ Gyr ago, in a scenario that supports the observed radio relic position at the cluster outskirts. However, the same analysis showed that the companion cluster, eFEDS J093501.1+005418, is not gravitationally bound to the interacting system and therefore it is not part of the supercluster. We also checked the impact of adopting a scaling relation to determine the halo concentration $c_{200}$. At the observed merger stage, where the clusters have travelled $\sim$55 per cent of the path to reach the apoapsis, the choice of the $c_{200}$ (whether from a scaling relation or a free parameter in the mass model) does not change significantly either the cluster masses or the kinematic description.