Exemplary Merging Clusters II: XMM-Newton and Chandra X-ray Observations of MACS J1752.0+4440 and ZwCl 1856.8+6616
Abstract
Using deep XMM-Newton and Chandra observations, we compare the double-radio-relic galaxy cluster mergers MACS J1752.0+4440 and ZwCl 1856.8+6616. Both are 1:1 mass-ratio mergers with similar relic separations but differing nearly an order of magnitude in total mass. In MACS J1752.0+4440, the surface-brightness discontinuity at the northeastern relic yields Mach Mρ=1.4±0.2, while the temperature jump provides a weaker constraint, corresponding to MkT≲2.3 at the 2σ level, lower than the radio-derived Mradio=3.1±0.1. No discontinuity is detected at the southwestern relic. Thermodynamic maps and axial profiles reveal surviving relatively low-entropy cores embedded in Mpc-scale stripped-gas structures. The nearly uniform X-ray tail brightness and a southwestern plateau coincident with a third lensing mass peak favor a non-zero impact parameter and complex assembly history. In ZwCl 1856.8+6616, we do not detect a clear surface brightness discontinuity at either relic. The northern X-ray peak leads its brightest cluster galaxy (BCG) and lensing peak, while the hotter southern X-ray peak is laterally offset from its BCG and lensing peak. The asymmetric intracluster emission favors a phase near or after first apocenter, when displaced gas can develop a slingshot-like morphology. We present two TNG-Cluster analogs in which a minor merger followed by an off-axis major collision produces extended X-ray tails resembling MACS J1752.0+4440 and later leads to gas structures resembling ZwCl 1856.8+6616. X-ray morphology independently confirms the merger phases inferred from relic-based chronometry, placing MACS J1752.0+4440 before and ZwCl 1856.8+6616 after first apocenter, and demonstrating that similar relic and lensing configurations can correspond to distinct dynamical states.
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BibTeX
@misc{hyeonghan2026exemplary,
title = {{Exemplary Merging Clusters II: XMM-Newton and Chandra X-ray Observations of MACS J1752.0+4440 and ZwCl 1856.8+6616}},
author = {K. HyeongHan and K. Finner and W. Lee and E. Silich and W. Forman and C. Jones and A. Tümer and S. Randall and J. ZuHone and M. James Jee and D. Wittman and R. J. van Weeren and M. Troxel},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10680},
eprint = {2610.10680},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10680},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Exemplary Merging Clusters II: XMM-Newton and Chandra X-ray Observations of MACS J1752.0+4440 and ZwCl 1856.8+6616
AU - K. HyeongHan
AU - K. Finner
AU - W. Lee
AU - E. Silich
AU - W. Forman
AU - C. Jones
AU - A. Tümer
AU - S. Randall
AU - J. ZuHone
AU - M. James Jee
AU - D. Wittman
AU - R. J. van Weeren
AU - M. Troxel
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.10680
UR - https://arxiv.org/abs/2610.10680
AB - Using deep XMM-Newton and Chandra observations, we compare the double-radio-relic galaxy cluster mergers MACS J1752.0+4440 and ZwCl 1856.8+6616. Both are 1:1 mass-ratio mergers with similar relic separations but differing nearly an order of magnitude in total mass. In MACS J1752.0+4440, the surface-brightness discontinuity at the northeastern relic yields Mach M_ρ=1.4±0.2, while the temperature jump provides a weaker constraint, corresponding to M_kT≲2.3 at the 2σ level, lower than the radio-derived M_radio=3.1±0.1. No discontinuity is detected at the southwestern relic. Thermodynamic maps and axial profiles reveal surviving relatively low-entropy cores embedded in Mpc-scale stripped-gas structures. The nearly uniform X-ray tail brightness and a southwestern plateau coincident with a third lensing mass peak favor a non-zero impact parameter and complex assembly history. In ZwCl 1856.8+6616, we do not detect a clear surface brightness discontinuity at either relic. The northern X-ray peak leads its brightest cluster galaxy (BCG) and lensing peak, while the hotter southern X-ray peak is laterally offset from its BCG and lensing peak. The asymmetric intracluster emission favors a phase near or after first apocenter, when displaced gas can develop a slingshot-like morphology. We present two TNG-Cluster analogs in which a minor merger followed by an off-axis major collision produces extended X-ray tails resembling MACS J1752.0+4440 and later leads to gas structures resembling ZwCl 1856.8+6616. X-ray morphology independently confirms the merger phases inferred from relic-based chronometry, placing MACS J1752.0+4440 before and ZwCl 1856.8+6616 after first apocenter, and demonstrating that similar relic and lensing configurations can correspond to distinct dynamical states.
ER -