Enlightening the structure and dynamics of Abell 1942

TL;DR

This study provides a detailed dynamical and X-ray analysis of galaxy cluster Abell 1942, revealing its relaxed state, substructures, and background influences, with new velocity and temperature measurements.

Contribution

It offers the first comprehensive dynamical and X-ray characterization of Abell 1942, including improved velocity, redshift, and temperature data, and clarifies the nature of observed weak lensing signals.

Findings

Cluster is well relaxed within 1.5 Mpc radius.

Two optical substructures are identified but not confirmed kinematically.

Background sources explain the weak lensing signal previously attributed to a dark clump.

Abstract

We present a dynamical analysis of the galaxy cluster Abell 1942 based on a set of 128 velocities obtained at the European Southern Observatory. Data on individual galaxies are presented and the accuracy of the determined velocities is discussed as well as some properties of the cluster. We have also made use of publicly available Chandra X-ray data. We obtained an improved mean redshift value z = 0.22513 \pm 0.0008 and velocity dispersion sigma = 908^{+147}_{-139} km/s. Our analysis indicates that inside a radius of ~1.5 h_{70}^{-1} Mpc (~7 arcmin) the cluster is well relaxed, without any remarkable feature and the X-ray emission traces fairly well the galaxy distribution. Two possible optical substructures are seen at ~5 arcmin from the centre towards the Northwest and the Southwest direction, but are not confirmed by the velocity field. These clumps are however, kinematically bound to the main structure of Abell 1942. X-ray spectroscopic analysis of Chandra data resulted in a temperature kT = 5.5 \pm 0.5 keV and metal abundance Z = 0.33 \pm 0.15 Z_odot. The velocity dispersion corresponding to this temperature using the T_X-sigma scaling relation is in good agreement with the measured galaxies velocities. Our photometric redshift analysis suggests that the weak lensing signal observed at the south of the cluster and previously attributed to a "dark clump", is produced by background sources, possibly distributed as a filamentary structure.