Resonant scattering at the center of the galaxy cluster PKS 0745-191 with XRISM

TL;DR

This study uses XRISM observations to detect resonant scattering in the galaxy cluster PKS 0745-191, providing insights into intracluster medium turbulence and demonstrating XRISM's capabilities for such analyses.

Contribution

First detection of resonant scattering effects in PKS 0745-191 with XRISM, offering a new method to constrain turbulence in galaxy clusters.

Findings

22% suppression of Fe XXV resonance line in the core

Resonant scattering results agree with line broadening measurements

Demonstrates XRISM's potential for turbulence studies

Abstract

We report evidence for the resonant scattering effect at the center of the galaxy cluster PKS 0745-191 with XRISM. We analyzed XRISM/Resolve commissioning-phase observations of the distant cluster PKS 0745-191 (z = 0.103) with a 54 ks exposure. The gain drift was corrected using the onboard modulated X-ray source (MXS), and spectra were extracted from all pixels well illuminated by MXS, the core region (four central pixels, about 100 kpc), and the surrounding region. A single-temperature collisional ionization equilibrium (CIE) model fits the full field-of-view spectrum with kT about 6 keV and a turbulent velocity of about 120 km/s. From the core (r < 50 kpc) spectrum, we detect about 22 percent suppression of the Fe XXV He-alpha resonance (w) line relative to the CIE prediction. We performed Monte Carlo simulations to calculate the resonant scattering (RS) effect using radial profiles from Chandra data. The RS-inferred turbulence agrees with that inferred from Resolve line broadening, demonstrating that RS provides an independent and consistent constraint on ICM turbulence. These results highlight the potential of XRISM/Resolve for turbulence studies in galaxy clusters.