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

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 ( (Formula presented) kT=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 × 10⁶⁰ erg, consistent with the energy associated with the central radio source. The kinetic energy injection rate is 6.9 × 10⁴⁴–7.4 × 10⁴⁵ 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.