A Brush with Turbulence: Probing the ICM Dynamics in the Merging Toothbrush Cluster using XRISM

@misc{madangarli2026brush,
  title = {{A Brush with Turbulence: Probing the ICM Dynamics in the Merging Toothbrush Cluster using XRISM}},
  author = {Anjali Madangarli and Aurora Simionescu and Huub Röttgering and Anwesh Majumder and Soeda Haruse and Kazuhiro Nakazawa and Yuusuke Uchida and Daisuke Ito and Gianfranco Brunetti and Reinout van Weeren and Congyao Zhang and Kamlesh Rajpurohit and Priyanka Chakraborty and Hiroki Akamatsu},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.05351},
  eprint = {2610.05351},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.05351},
}

TY  - UNPB
TI  - A Brush with Turbulence: Probing the ICM Dynamics in the Merging Toothbrush Cluster using XRISM
AU  - Anjali Madangarli
AU  - Aurora Simionescu
AU  - Huub Röttgering
AU  - Anwesh Majumder
AU  - Soeda Haruse
AU  - Kazuhiro Nakazawa
AU  - Yuusuke Uchida
AU  - Daisuke Ito
AU  - Gianfranco Brunetti
AU  - Reinout van Weeren
AU  - Congyao Zhang
AU  - Kamlesh Rajpurohit
AU  - Priyanka Chakraborty
AU  - Hiroki Akamatsu
PY  - 2026
DA  - 2026/10/04
PB  - arXiv
DO  - 10.48550/arxiv.2610.05351
UR  - https://arxiv.org/abs/2610.05351
AB  - The Toothbrush Cluster (1RXS J0603.3+4214) is known for its northern radio relic, radio halo, and highly disturbed X-ray morphology. It shows features of both shock-driven and turbulent reacceleration, the latter of which is invoked to explain its radio halo. However, how kinetic energy from the merger is distributed into gas motions across spatial scales remains unclear. We probe the intracluster medium (ICM) dynamics in the southern, X-ray-brightest region of the cluster using a 167 ks XRISM/Resolve observation. We conduct both full-array and quadrant sub-array analyses by fitting the spectra with single and multi-component thermal models in the 3-8 keV band. The full-array spectrum favours two ICM components with a transonic line-of-sight (LOS) velocity difference of Δv_bulk=1635^+165_−110 km s^−1, while the velocity dispersions are much lower, at σ_v,1D∼245-310 km s^−1. The sub-array analysis likewise reveals multiple components in at least three quadrants, with LOS bulk velocities ranging from −2520^+295_−230 to +930^+70_−110 km s^−1. The velocity dispersions remain modest at ∼215 km s^−1, corresponding to a turbulent pressure support of about 3-6% on scales dominating the observed line broadening. Cooler gas is detected in the NE and SW, with kT_NE=3.13^+0.33_−0.30 keV and kT_SW=2.32^+0.43_−0.37 keV, likely associated with a third, northern subcluster identified in weak-lensing and optical studies. Our results indicate a complex ICM kinematic structure, with evidence for at least three subclusters exhibiting supersonic bulk velocity offsets and much smaller velocity dispersions. This shows that the merger geometry has a significant line-of-sight component and may indicate that the cluster collision is relatively young, with the turbulent cascade not yet fully established.
ER  -