The dynamical state of Abell 2399: a bullet-like cluster

TL;DR

This study investigates the dynamical state of galaxy cluster Abell 2399 using multi-wavelength data, substructure analysis, and hydro-dynamical simulations, revealing a recent merger with complex ICM properties and metallicity distribution.

Contribution

It combines optical, X-ray, and simulation analyses to characterize the merger stage and substructure of Abell 2399, providing new insights into its dynamical history.

Findings

ICM shows asymmetry and temperature/pressure enhancements indicating recent merging.

Optical analysis identifies two main substructures consistent with X-ray data.

Secondary clump has higher metallicity, suggesting recent interaction effects.

Abstract

While there are many ways to identify substructures in galaxy clusters using different wavelengths, each technique has its own caveat. In this paper, we conduct a detailed substructure search and dynamical state characterisation of Abell 2399, a galaxy cluster in the local Universe ($z \sim 0.0579$), by performing a multi-wavelength analysis and testing the results through hydro-dynamical simulations. In particular, we apply a Gaussian Mixture Model to the spectroscopic data from SDSS, WINGS, and Omega WINGS Surveys to identify substructures. We further use public \textit{XMM-Newton} data to investigate the intracluster medium (ICM) thermal properties, creating temperature, metallicity, entropy, and pressure maps. Finally, we run hydro-dynamical simulations to constrain the merger stage of this system. The ICM is very asymmetrical and has regions of temperature and pressure enhancement that evidence a recent merging process. The optical substructure analysis retrieves the two main X-ray concentrations. The temperature, entropy, and pressure are smaller in the secondary clump than in the main clump. On the other hand, its metallicity is considerably higher. This result can be explained by the scenario found by the hydro-dynamical simulations where the secondary clump passed very near to the centre of the main cluster possibly causing the galaxies of that region to release more metals through the increase of ram-pressure stripping.16