X-ray study of the merging galaxy cluster Abell 3411-3412 with XMM-Newton and Suzaku

TL;DR

This study uses XMM-Newton and Suzaku X-ray observations to analyze the thermodynamic properties of the merging galaxy cluster Abell 3411-3412, revealing shock features and temperature profiles that support re-acceleration scenarios and provide insights into cluster dynamics.

Contribution

The paper introduces a new calibration method for XMM-Newton soft proton background and combines multi-mission data to accurately characterize X-ray edges and temperature profiles in a merging galaxy cluster.

Findings

Detected a $ ext{M} ext{~}1.2$ shock at the south-eastern edge supporting re-acceleration.

Observed complex shock and cold material interactions at the southern edge.

Measured lower cluster temperatures than previous Chandra estimates.

Abstract

Context: Chandra observations of the Abell 3411-3412 merging system have revealed an outbound bullet-like sub-cluster in the northern part and many surface brightness (SB) edges at the southern periphery, where multiple diffuse sources are also reported from radio observations. Notably, a south-eastern radio relic associated with fossil plasma from a radio galaxy and with a detected X-ray edge provides direct evidence of shock re-acceleration. The properties of the reported X-ray edges have yet to be constrained from a thermodynamic view. Aims: We use the XMM-Newton and Suzaku observations to reveal the thermodynamical nature of the reported re-acceleration site and other X-ray edges. Meanwhile, we aim to investigate the temperature profile in the low-density outskirts with Suzaku data. Methods: We perform both imaging and spectral analysis to measure the density jump and the temperature jump across multiple known X-ray SB discontinuities. We present a new method to calibrate the XMM-Newton soft proton background. Archival Chandra, Suzaku, and ROSAT data are used to estimate the cosmic X-ray background and Galactic foreground levels with improved accuracy compared to standard blank sky spectra. Results: At the south-eastern edge, both XMM-Newton and Suzaku's temperature jumps point to a $\mathcal{M}\sim1.2$ shock, which agrees with result from SB fits with Chandra, and supports the re-acceleration scenario at this shock front. The southern edge shows a more complex scenario, where a shock and the presence of stripped cold material may coincide. The Suzaku temperature profiles in the southern low density regions are marginally higher than the typical relaxed cluster temperature profile. The measured value $kT_{500}=4.84\pm0.04\pm0.19$ keV with XMM-Newton and $kT_{500}=5.17\pm0.07\pm0.13$ keV with Suzaku are significantly lower than previously inferred from Chandra.