Vigorous turbulence driven by quasar-mode feedback in a cluster core

Satoshi Yamada, Shutaro Ueda, Hirofumi Noda, Yutaka Fujita, Misaki Mizumoto, Kentaro Nagamine, Claudio Ricci, Shoji Ogawa, Taiki Kawamuro, Shinya Yamada, Yuichi Terashima, Yoshihiro Ueda

First listed 2026-07-29 | Last updated 2026-07-27

Abstract

Quasars are among the most luminous objects. They are powered by accretion onto supermassive black holes. They are thought to impact cosmological evolution primarily through energetic winds, known as quasar-mode feedback, yet the efficiency and spatial extent of this process remain poorly constrained. Here we present X-Ray Imaging and Spectroscopy Mission (XRISM) observations of H1821+643---the nearest galaxy cluster with a central quasar (redshift z = 0.297)---which was a rare opportunity to directly probe quasar-mode feedback in the intracluster medium. High-resolution spectroscopy reveals exceptionally broadened Fe XXV emission lines from the intracluster medium, with a velocity dispersion of approximately 300 km/s, far exceeding values observed in nearby cluster cores. These lines originate predominantly at radii of 20-100 kpc from the centre. Assuming that turbulence from a quasar-driven shock led to the broadening of the lines, the energy injected by the quasar beyond galactic scales ($\gtrsim$20 kpc) is estimated to be $\gtrsim$1-10% of its radiative energy. Notably, this feedback efficiency exceeds previous multiwavelength estimates by orders of magnitude ($\lesssim$0.01%) and reaches the levels required by the latest cosmological hydrodynamical simulations. This finding of vigorous turbulence indicates that quasar-mode feedback plays a central role in regulating galaxy and cluster evolution at high redshift.

Short digest

XRISM/Resolve spectroscopy of the z=0.297 quasar cluster H1821+643 detects Fe XXV emission from the intracluster medium broadened to a line-of-sight velocity dispersion of about 300 km s⁻¹, markedly above the relatively quiescent cores measured by Hitomi and XRISM. Spatial-spectral mixing analysis places most of this broad-line emission at projected radii of 20–100 kpc, separating it from the luminous nuclear quasar despite Resolve’s broad point-spread function. Interpreting the motions as turbulence and shear driven by a quasar-powered shock implies that roughly 1–10% of the quasar’s radiative output is coupled beyond galactic scales, bringing quasar-mode feedback into the efficiency range required in cosmological simulations.

Key figures to inspect

• Figure 1. The Resolve Fe XXV spectrum provides the paper’s direct observational result: H1821+643 has a visibly broader ICM line profile than the Perseus core, establishing unusually strong turbulence or velocity shear around a radio-quiet quasar.
• Figure 2. This spatial-spectral decomposition is essential for locating the signal. It shows how the authors account for PSF leakage and infer that the broad Fe-line emission predominantly arises from ICM at 20–100 kpc rather than from the quasar nucleus.
• Figure 3. The comparison of non-thermal energy fraction against AGN luminosity puts H1821+643 in population context: it combines the brightest X-ray AGN with the largest inferred gas-motion energy fraction among the XRISM and Hitomi cluster sample.
• Figure 4. The schematic distills the physical interpretation linking a quasar-driven wind and forward shock to enhanced 20–100 kpc ICM turbulence, and clarifies why the measured velocity dispersion implies efficient feedback beyond the host galaxy.