XRISM mock observations of simulated AGN jets in the core of a galaxy cluster

TL;DR

This study uses simulated X-ray observations to analyze how AGN jets interact with the intracluster medium, revealing viewing angle effects on observed velocity dispersion and emphasizing the importance of shock and cocoon structures.

Contribution

First detailed mock XRISM observations of AGN jet interactions with the ICM based on hydrodynamic simulations, highlighting viewing angle effects on spectral features.

Findings

Velocity dispersion is minimized when observing along the jet direction.

Rapidly expanding jet heads contribute little to X-ray emission due to high temperature and low density.

Results inform interpretation of XRISM data for AGN feedback studies.

Abstract

Jets from active galactic nuclei (AGNs) are expected to heat the surrounding intracluster medium (ICM). We investigate how the interaction between jets and the ICM appears in high-resolution X-ray observations using mock X-ray observations based on two-dimensional hydrodynamic simulations. We constructed a model of an active galactic nucleus (AGN) similar to Cygnus A (Cyg A), a powerful FR II radio galaxy. Our simulations model bipolar jets propagating into a stratified ICM, forming forward shocks and low-density cocoons. Based on these results, we generate synthetic spectra that incorporate both shocked and unshocked ICM components. Then, we perform mock observations using the XRISM/Resolve X-ray spectrometer. We focus particularly on viewing angle effects. Our mock observations revealed that the smallest line broadening, observed as velocity dispersion, associated with the cocoon's bulk expansion occurs when observing along the jet direction, where the expansion velocity is highest. Although this may appear counterintuitive, it occurs because the rapidly expanding jet head contributes little to X-ray emission due to its high temperature and low density. Our results highlight the importance of considering the temperature and density structure of AGN-driven shocks and cocoons when interpreting XRISM data. These findings lay the groundwork for XRISM's observations of AGN jets and will improve our understanding of AGN feedback processes in galaxy clusters.