Measuring the intracluster medium velocity structure within the A3266 galaxy cluster

¹ Max-Planck-Institut für Extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching, Germany
² Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK
³ INAF – IASF Palermo, Via U. La Malfa 153, I-90146 Palermo, Italy
⁴ School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
⁵ Department of Astronomy, University of Geneva, Ch. d’Ecogia 16, CH-1290 Versoix, Switzerland
⁶ Department of Physics and Astronomy, University of Alabama in Huntsville, Huntsville, AL 35899, USA
⁷ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁸ Department of Astrophysical Sciences, Princeton University, NJ, 08544, USA

^⋆ Corresponding author; egatuzz@mpe.mpg.de

Received: 24 July 2024
Accepted: 6 November 2024

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 an adaptively smoothed GGM filter applied to the EPIC-pn X-ray image. Then, we applied a novel XMM-Newton EPIC-pn energy scale calibration, which uses instrumental Cu Kα as a reference for the line emission, to measure the line-of-sight velocities of 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 demonstrates 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 ± 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 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.