Dynamics of AGN feedback in the X-ray bright eastern and southwestern “arms” of M87, mapped by XRISM

Context. Feedback from active galactic nuclei (AGN) plays a critical role in regulating gas cooling and star formation in massive galaxies and at the centers of galaxy clusters. As the central galaxy in the nearest cluster, M87 provides the best spatial resolution for disentangling the complex interactions between AGN jets and the surrounding environment. Aims. We investigate the velocity structure of the multi-temperature X-ray gas in M87, particularly in the eastern and southwestern “arms” associated with past AGN outbursts, using high-resolution spectroscopy from XRISM/Resolve. Methods. We analyzed a mosaic of XRISM/Resolve observations covering the core of M87, fitting single- and multi-temperature models to spectra extracted from different regions and energy bands. We assessed the line-of-sight velocities and velocity dispersions of the hotter ambient and cooler uplifted gas phases, and evaluated systematic uncertainties related to instrumental gain calibration. Results. The hotter intracluster medium (ICM) phase, traced by Fe He-α emission, shows velocity dispersions below ∼100 km/s, and no significant velocity shifts between the arms and a relaxed offset region, suggesting limited dynamical impact from older AGN lobes. In contrast, the cooler gas phase appears to exhibit larger line-of-sight velocity gradients up to several hundred km/s as well as a higher velocity dispersion than the ambient hot phase, although these conclusions remain tentative pending improvements in the robustness of the gain calibration at lower energies. Conclusions. The first microcalorimeter-resolved map of gas dynamics in M87 supports the uplift scenario for the X-ray arms, with the cooler gas in the east and southwest seemingly moving in opposite directions along the line-of-sight. The kinetic energy is a small fraction of the gravitational potential energy associated with the gas uplift, and XRISM further suggests that AGN-driven motions may be short-lived in the hot ambient ICM. These constraints provide important input toward shaping future models of AGN feedback.