Measuring the ICM velocity structure within the A3266 galaxy cluster

TL;DR

This paper analyzes the velocity structure of the hot intracluster medium in galaxy cluster A3266 using new X-ray observations, novel calibration, and velocity mapping to understand its dynamic processes.

Contribution

It introduces a new calibration method for XMM-Newton EPIC-pn data and provides detailed velocity maps and analysis of the ICM in A3266, revealing systemic redshifted velocities.

Findings

Hot gas shows a systemic redshifted velocity relative to the cluster.

Redshifted velocities extend up to 1125 kpc from the core.

Velocity distribution follows an unimodal normal distribution.

Abstract

We present a detailed analysis of the velocity structure of the hot intracluster medium (ICM) within the A3266 galaxy cluster, including new observations taken between June and November 2023. Firstly, morphological structures within the galaxy cluster were examined using a Gaussian Gradient Magnitude (GGM) and adaptively smoothed GGM filter applied to the EPIC-pn X-ray image. Then, we applied a novel {\it XMM-Newton} EPIC-pn energy scale calibration, which uses instrumental Cu K$\alpha$ as reference for the line emission, to measure line-of-sight velocities of the hot gas within the system. This approach enabled us to create two-dimensional projected maps for velocity, temperature, and metallicity, showing that the hot gas displays a redshifted systemic velocity relative to the cluster redshift across all fields of view. Further analysis of the velocity distribution through non-overlapping circular regions demonstrated consistent redshifted velocities extending up to 1125 kpc from the cluster core. Additionally, the velocity distribution was assessed along regions following surface brightness discontinuities, where we observed redshifted velocities in all regions, with the largest velocities reaching $768 \pm 284$ km/s. Moreover, we computed the velocity Probability Density Function (PDF) from the velocity map. We applied a normality test, finding that the PDF adheres to an unimodal normal distribution consistent with theoretical predictions. Lastly, we computed a velocity structure function (VSF) for this system using the measured line-of-sight velocities. These insights advance our understanding of the dynamic processes within the A3266 galaxy cluster and contribute to our broader knowledge of ICM behavior in merging galaxy clusters.