A new method to measure the mass of galaxy clusters

TL;DR

This paper introduces a novel method for measuring galaxy cluster masses using kinematic data from structures outside the virialized region, providing an alternative to traditional equilibrium-based techniques.

Contribution

The paper presents a new approach that infers cluster mass by analyzing the motion of external structures like sheets and filaments, independent of assumptions about equilibrium.

Findings

Successfully tested with cosmological simulations.

Applied to the Coma cluster with consistent results.

Provides accurate 3D orientation of external structures.

Abstract

The mass measurement of galaxy clusters is an important tool for the determination of cosmological parameters describing the matter and energy content of the Universe. However, the standard methods rely on various assumptions about the shape or the level of equilibrium of the cluster. We present a novel method of measuring cluster masses. It is complementary to most of the other methods, since it only uses kinematical information from outside the virialized cluster. Our method identifies objects, as galaxy sheets or filaments, in the cluster outer region, and infers the cluster mass by modeling how the massive cluster perturbs the motion of the structures from the Hubble flow. At the same time, this technique allows to constrain the three-dimensional orientation of the detected structures with a good accuracy. We use a cosmological numerical simulation to test the method. We then apply the method to the Coma cluster, where we find two galaxy sheets, and measure the mass of Coma to be Mvir=(9.2\pm2.4)10^{14} Msol, in good agreement with previous measurements obtained with the standard methods.