XRISM observations of the Perseus cluster along two arms: Chaotic ICM motions probed by resonant scattering

@misc{heinrich2026xrism,
  title = {{XRISM observations of the Perseus cluster along two arms: Chaotic ICM motions probed by resonant scattering}},
  author = {Annie Heinrich and Irina Zhuravleva and Congyao Zhang and Anna Ogorzalek and Ayşegül Tümer and François Mernier and Phillip C. Stancil and Elena Bellomi and Lior Shefler and John ZuHone and Yutaka Fujita and Julie Hlavacek-Larrondo and Yuto Ichinohe and Kyoko Matsushita and Nhut Truong and Shutaro Ueda},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.10845},
  eprint = {2609.10845},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.10845},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - XRISM observations of the Perseus cluster along two arms: Chaotic ICM motions probed by resonant scattering
AU  - Annie Heinrich
AU  - Irina Zhuravleva
AU  - Congyao Zhang
AU  - Anna Ogorzalek
AU  - Ayşegül Tümer
AU  - François Mernier
AU  - Phillip C. Stancil
AU  - Elena Bellomi
AU  - Lior Shefler
AU  - John ZuHone
AU  - Yutaka Fujita
AU  - Julie Hlavacek-Larrondo
AU  - Yuto Ichinohe
AU  - Kyoko Matsushita
AU  - Nhut Truong
AU  - Shutaro Ueda
PY  - 2026
DA  - 2026/09/09
PB  - arXiv
DO  - 10.48550/arxiv.2609.10845
UR  - https://arxiv.org/abs/2609.10845
AB  - XRISM has mapped gas velocities across the core of the Perseus cluster, separating the kinematic effects of mergers and AGN feedback. The physical properties of these motions remain unclear: are they a superposition of bulk flows, predominantly random/turbulent motions, or a mixture of both? Without resolving this question, constraints on the nonthermal pressure fraction and heating rate remain uncertain, as both assume predominantly random motions. Unlike emission line broadening, resonant scattering is most sensitive to small-scale, random motions rather than coherent bulk flows. Taking advantage of the extensive XRISM coverage of the Perseus cluster, we detect the full effects of resonant scattering on the Heα w line for the first time. This includes flux suppression in the cluster center, enhancement in the outer regions, and non-Gaussianity in the emission line. We employ radiative transfer simulations to constrain the amplitude of small-scale ICM velocities in the inner 60 kpc of Perseus, finding them to be consistent with the line broadening measurements within the uncertainties. This indicates the observed velocity dispersion is primarily due to small-scale random motions in the central Perseus regions rather than coherent bulk flows. We further explore potential anisotropy of these motions, showing that they are consistent with isotropic or radial motions rather than tangential ones. Longer XRISM observations are required to improve these anisotropy constraints. Finally, we explore azimuthal variations between the two complete radial arms observed by XRISM.
ER  -