Dynamical analysis of galaxy cluster merger Abell 2146

TL;DR

This paper provides a detailed dynamical analysis of the galaxy cluster merger Abell 2146, revealing its shock fronts, mass, and merger geometry through spectroscopy and X-ray data, and estimating the merger timeline.

Contribution

It offers the first comprehensive dynamical model of Abell 2146 combining spectroscopic, X-ray, and statistical analyses to determine merger geometry and timescale.

Findings

Two shock fronts identified in the system.

Merger axis is close to the plane of the sky.

Merger occurred approximately 0.24-0.28 Gyr ago.

Abstract

We present a dynamical analysis of the merging galaxy cluster system Abell 2146 using spectroscopy obtained with the Gemini Multi-Object Spectrograph on the Gemini North telescope. As revealed by the Chandra X-ray Observatory, the system is undergoing a major merger and has a gas structure indicative of a recent first core passage. The system presents two large shock fronts, making it unique amongst these rare systems. The hot gas structure indicates that the merger axis must be close to the plane of the sky and that the two merging clusters are relatively close in mass, from the observation of two shock fronts. Using 63 spectroscopically determined cluster members, we apply various statistical tests to establish the presence of two distinct massive structures. With the caveat that the system has recently undergone a major merger, the virial mass estimate is M_vir = 8.5 +4.3 -4.7 x 10 ^14 M_sol for the whole system, consistent with the mass determination in a previous study using the Sunyaev-Zeldovich signal. The newly calculated redshift for the system is z = 0.2323. A two-body dynamical model gives an angle of 13-19 degrees between the merger axis and the plane of the sky, and a timescale after first core passage of 0.24-0.28 Gyr.