Spectrally Resolved Gas Kinematics in Cygnus A: XRISM Detects AGN Jet-induced Velocity Dispersion in Multitemperature Gas

Abstract We report spectral analysis on a 170 ks XRISM Resolve exposure of the core of Cygnus A. Analyzing the full field of view spectrum in the 1.7–12.0 keV band, we find evidence for two-temperature cluster gas. The hotter ( kT = 5.53 ± 0.13 keV) gas has a velocity dispersion of 261 ± 13 km s −1 and a bulk velocity of 120 ± 20 km s −1 with respect to the central galaxy. The cooler gas ( k T = 2 . 0 − 0.3 + 0.4 keV) has an even broader velocity dispersion of 440 ± 130 km s −1 , with a systematic uncertainty of 120 km s −1 . The relative line-of-sight velocity between the hotter and cooler gas can be as high as 450 ± 140 km s −1 . We interpret the high velocity dispersions as a combination of turbulence and bulk motion due to the cocoon shock. The upper limit on the nonthermal pressure fraction for the hotter gas is 7.7% ± 0.7%. We associate the cooler gas with the central region (<35 kpc) and the hotter phase with the gas surrounding it (35–100 kpc). The total energy due to the kinetic motion is 5.1 × 10 60 erg, consistent with the energy associated with the central radio source. The kinetic energy injection rate is 6.9 × 10 44 –7.4 × 10 45 erg s −1 under varying assumptions of injection timescales. The range of injection power is higher than the cooling luminosity, and thus the heating and cooling rates in Cygnus A are unbalanced.