# Characterization of diffuse X-ray emission from IGR~J17448-3232: an implication of a line of sight merging activity

## TL;DR

This study analyzes the diffuse X-ray emission from galaxy cluster IGR J17448-3232, revealing non-ionization equilibrium conditions likely caused by a line-of-sight merging event, with detailed spectral modeling of the intracluster medium.

## Contribution

It provides the first detailed spectral analysis indicating NEI plasma in IGR J17448-3232 and links this to a merging activity along the line of sight.

## Key findings

- ICM in the core has high electron temperature (~13-15 keV)
- Outer region shows lower temperature (5-8 keV)
- Evidence suggests a line-of-sight merging event

## Abstract

Results of the spectral analysis for the galaxy cluster IGR J17448-3232 are presented. The intracluster medium (ICM) in the central region (r<300", 320 kpc) has a high electron temperature plasma of kTe~13-15 keV and an ionization temperature estimated from an intensity ratio of Fe XXVI Ly alpha/Fe XXV He alpha lines is lower than the electron temperature, which suggests that the ICM is in the non-ionization equilibrium (NEI) state. The spectrum in the central region can be also fitted with a two-component model: a two-temperature plasma model in a collisional ionization equilibrium (CIE) with temperatures of 7.9 keV and >34 keV or a CIE+power law model with a temperature of 9.4 keV and a photon index of 1.1. The two component models can represent the intensity ratio of Fe XXVI Ly alpha/Fe XXV He alpha lines. On the other hand, the spectrum in the outer region (r>300'') can be explained by a single CIE plasma model with a temperature of 5-8 keV. Based on the spectral feature and its circular structure, we propose that the NEI plasma was produced by merging along the line-of-sight direction.