Directional miscentering dependence in weak lensing mass bias

TL;DR

This paper investigates how non-isotropic miscentering affects weak lensing mass estimates of galaxy clusters and proposes using the center of mass instead of the potential minimum to reduce bias.

Contribution

It demonstrates that considering the center of mass instead of the potential minimum significantly reduces non-isotropic mass bias in weak lensing measurements.

Findings

Non-isotropic miscentering can cause significant mass bias.

Using the center of mass reduces bias to within 1%.

Simulation results support improved mass estimation accuracy.

Abstract

Galaxy cluster masses estimated from parametric modeling of weak lensing shear observations are known to be biased by inaccuracies in observationally determined centers. It has recently been shown that such systematic effects can be non-isotropic when centers are derived from X-ray or Compton-Y (Sunyaev-Zeldovich effect) observations, which is often the case in practice. This fact challenges current methods of accurately correcting for weak lensing mass biases using simulations paired with isotropic empirical miscentering distributions, in particular as the effect on determined masses is currently a dominant source of systematic uncertainty. We use hydrodynamical cosmological simulations taken from the Magneticum Pathfinder simulations to show that the non-isotropic component of the mass bias can be reduced to within one percent of the mass when considering the center of mass, rather than the bottom of the gravitational potential, as the reference center of a galaxy cluster.