TNGC-SIDM I: Evolution of massive cluster mergers under the self-interacting dark matter paradigm
Abstract
Merging galaxy clusters provide an ideal laboratory for testing the self-interacting nature of dark matter. In this paper, we present a pilot study of magnetohydrodynamical cosmological zoom-in simulations of two cluster mergers selected from TNG-Cluster, with M200c ∼ 9×1014 M⊙ and M200c∼ 2×1014 M⊙. The simulations are performed with both standard collisionless cold dark matter (CDM) and self-interacting dark matter (SIDM), assuming an isotropic, velocity-independent cross-section of σT/mχ= 1 cm2 g−1, with an additional 0.5 cm2 g−1 run for the low-mass system, and the mass resolution and galaxy formation model are unchanged from TNG-Cluster. We show how dark matter self-interactions produce an isothermal core in the dark matter halo, generate unique substructures in the intracluster light, and introduce variation in the multi-wavelength observables of the intracluster plasma. Using these simulations, we test the validity of observational probes for dark matter self-interactions in cluster mergers. We find that the shock-to-shock separation shows similar evolution in the self-interaction models tested here, providing a reference for distinguishing the ∼100−200 kpc-scale difference in halo separation induced by self-interactions. Moreover, the dark matter halo centroid of the main cluster in the massive cluster merger is offset from the brightest cluster galaxy by as much as ∼20 kpc, larger than the offset in the sub-cluster. This offset persists beyond 4 Gyr after the first pericenter passage. Our results indicate that sample selection plays a key role in testing the possible self-interacting nature of dark matter using cluster mergers, and that double radio relic cluster mergers and massive clusters with evidence of an ancient major merger offer a promising testbed for this purpose.
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BibTeX
@misc{lee2026tngcsidm,
title = {{TNGC-SIDM I: Evolution of massive cluster mergers under the self-interacting dark matter paradigm}},
author = {Wonki Lee and Dylan Nelson and Myungkook J. Jee and Giulia Despali and Mark Vogelsberger and Annalisa Pillepich and Cian Roche and Kyle Finner and Hyungjin Joo and Daisuke Nagai and John ZuHone},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18957},
eprint = {2610.18957},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18957},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - TNGC-SIDM I: Evolution of massive cluster mergers under the self-interacting dark matter paradigm
AU - Wonki Lee
AU - Dylan Nelson
AU - Myungkook J. Jee
AU - Giulia Despali
AU - Mark Vogelsberger
AU - Annalisa Pillepich
AU - Cian Roche
AU - Kyle Finner
AU - Hyungjin Joo
AU - Daisuke Nagai
AU - John ZuHone
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18957
UR - https://arxiv.org/abs/2610.18957
AB - Merging galaxy clusters provide an ideal laboratory for testing the self-interacting nature of dark matter. In this paper, we present a pilot study of magnetohydrodynamical cosmological zoom-in simulations of two cluster mergers selected from TNG-Cluster, with M_200c ∼ 9×10^14 M_⊙ and M_200c∼ 2×10^14 M_⊙. The simulations are performed with both standard collisionless cold dark matter (CDM) and self-interacting dark matter (SIDM), assuming an isotropic, velocity-independent cross-section of σ_T/m_χ= 1 cm^2 g^−1, with an additional 0.5 cm^2 g^−1 run for the low-mass system, and the mass resolution and galaxy formation model are unchanged from TNG-Cluster. We show how dark matter self-interactions produce an isothermal core in the dark matter halo, generate unique substructures in the intracluster light, and introduce variation in the multi-wavelength observables of the intracluster plasma. Using these simulations, we test the validity of observational probes for dark matter self-interactions in cluster mergers. We find that the shock-to-shock separation shows similar evolution in the self-interaction models tested here, providing a reference for distinguishing the ∼100−200 kpc-scale difference in halo separation induced by self-interactions. Moreover, the dark matter halo centroid of the main cluster in the massive cluster merger is offset from the brightest cluster galaxy by as much as ∼20 kpc, larger than the offset in the sub-cluster. This offset persists beyond 4 Gyr after the first pericenter passage. Our results indicate that sample selection plays a key role in testing the possible self-interacting nature of dark matter using cluster mergers, and that double radio relic cluster mergers and massive clusters with evidence of an ancient major merger offer a promising testbed for this purpose.
ER -