Gas Motions in Hydra-A: XRISM Constraints on ICM Kinematics Across Jet-Inflated Cavities
Abstract
We report on two deep XRISM observations of the central and northern regions of Hydra-A's X-ray atmosphere, covering the bubbles inflated by jets from the central galaxy's active galactic nucleus. We use spatial-spectral mixing, combining Chandra's high spatial resolution with XRISM's high spectral resolution, to investigate atmospheric kinematics. The velocity dispersion in the northern region, σv = 140+30−20 km s−1, is comparable to that in the central region (σv = 162 ± 10 km s−1). We show that motion of the large-scale cocoon shock front could be responsible for the large dispersion toward the north. The dispersion in the northeast quarter of the central pointing, σv = 260 ± 50 km s−1, is among the highest measured. This region contains an X-ray-bright feature previously identified as metal-rich, possibly gas uplifted in the wake of previous-generation cavities. Dispersions in all other quarter regions are low (σv ≤ 180 km s−1) and consistent with previous XRISM results from other objects. The kinetic energy at the center is comparable to the enthalpies of the cavities, while in the north it is roughly an order of magnitude smaller. The jet thus drives gas motion efficiently at smaller scales (r < 95 kpc) and inefficiently at larger scales (95−317 kpc toward the north along the jet). A bulk flow toward our line of sight of −100 ± 30 km s−1 in the southwest quarter of the central pointing, measured with respect to the central galaxy, is also observed, possibly due to sloshing. No significant bulk motion was detected in any other region.
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BibTeX
@misc{majumder2026motions,
title = {{Gas Motions in Hydra-A: XRISM Constraints on ICM Kinematics Across Jet-Inflated Cavities}},
author = {Anwesh Majumder and B. R. McNamara and P. E. J. Nulsen and H. Russell and T. Rose and T. Heckman and A. Simionescu and A. Fabian and M. W. Wise and N. Werner and M. McDonald},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.18315},
eprint = {2607.18315},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.18315},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Gas Motions in Hydra-A: XRISM Constraints on ICM Kinematics Across Jet-Inflated Cavities
AU - Anwesh Majumder
AU - B. R. McNamara
AU - P. E. J. Nulsen
AU - H. Russell
AU - T. Rose
AU - T. Heckman
AU - A. Simionescu
AU - A. Fabian
AU - M. W. Wise
AU - N. Werner
AU - M. McDonald
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2607.18315
UR - https://arxiv.org/abs/2607.18315
AB - We report on two deep XRISM observations of the central and northern regions of Hydra-A's X-ray atmosphere, covering the bubbles inflated by jets from the central galaxy's active galactic nucleus. We use spatial-spectral mixing, combining Chandra's high spatial resolution with XRISM's high spectral resolution, to investigate atmospheric kinematics. The velocity dispersion in the northern region, σ_v = 140^+30_−20 km s^−1, is comparable to that in the central region (σ_v = 162 ± 10 km s^−1). We show that motion of the large-scale cocoon shock front could be responsible for the large dispersion toward the north. The dispersion in the northeast quarter of the central pointing, σ_v = 260 ± 50 km s^−1, is among the highest measured. This region contains an X-ray-bright feature previously identified as metal-rich, possibly gas uplifted in the wake of previous-generation cavities. Dispersions in all other quarter regions are low (σ_v ≤ 180 km s^−1) and consistent with previous XRISM results from other objects. The kinetic energy at the center is comparable to the enthalpies of the cavities, while in the north it is roughly an order of magnitude smaller. The jet thus drives gas motion efficiently at smaller scales (r < 95 kpc) and inefficiently at larger scales (95−317 kpc toward the north along the jet). A bulk flow toward our line of sight of −100 ± 30 km s^−1 in the southwest quarter of the central pointing, measured with respect to the central galaxy, is also observed, possibly due to sloshing. No significant bulk motion was detected in any other region.
ER -