A Deep Chandra View of Abell 2597: Bubbles, Shocks, Cold Fueling, and a Plasma Depletion Layer
Osase Omoruyi, Grant Tremblay, Stefi A. Baum, Tracy E. Clarke, Pratik Dabhade, Andrew Fabian, Massimo Gaspari, Sanna Gulati, Preeti Kharb, Maxim Markevitch, Paul Nulsen, Christopher P. O'Dea, Scott Randall, Somak Raychaudhury, Sravani Vaddi, Alexey Vikhlinin, John Zuhone
TL;DR
Abell 2597 epitomizes a self-regulated AGN feedback cycle in a cool-core ICM. The study uses deep Chandra observations complemented by GMRT radio and SINFONI near-IR data to map seven X-ray cavities, one to three weak shocks out to ~150 kpc, and a potential plasma depletion layer, quantifying how mechanical AGN energy couples to the ICM. The energy input is $\\sim 10^{44}$ erg s$^{-1}$, roughly matching the cooling luminosity, yet radiative cooling persists at $\\sim 15\ M_{ m \\odot}\ { m yr}^{-1}$, implying an ongoing cold-gas supply. Bondi accretion power is estimated at $\\sim 2\\times 10^{43}$ erg s$^{-1}$, which is insufficient to power the observed cavities, favoring chaotic cold accretion as the dominant fueling channel, in agreement with ALMA CO observations. Altogether, the results support a turbulent, multiphase fueling scenario that sustains recurrent, self-regulated AGN feedback shaping the cluster core.
Abstract
To examine how AGN feedback shapes the intracluster medium (ICM) and fuels black hole accretion in the cool-core galaxy cluster Abell 2597, we present deep ($\sim$600 ks) Chandra X-ray observations complemented by archival GMRT radio and SINFONI near-infrared data. Radio-mode AGN activity has inflated seven X-ray cavities and driven one to three potential weak shocks ($M \sim 1.05-1.14$) extending to $\sim 150$ kpc, suggesting recurrent outbursts occurring on $\sim 10^7$ year timescales. We also detect a narrow, $\sim$57 kpc X-ray surface brightness deficit-a potential plasma depletion layer-likely shaped by residual sloshing motions that amplified magnetic fields and/or displaced gas within the cluster core. Although the AGN injects $\sim 10^{44}$ erg s$^{-1}$ of energy, comparable to the cluster's cooling luminosity, radiative cooling persists at $\sim$15 M$_{\odot} $yr$^{-1}$, replenishing the billion solar mass cold gas reservoir at the heart of the brightest cluster galaxy. Sustaining this level of activity requires a continuous fuel supply, yet the estimated Bondi accretion power ($\sim 2 \times 10^{43}$ erg s$^{-1}$) falls an order of magnitude short of the observed cavity power, suggesting that "hot" gas fueling is insufficient. Instead, archival ALMA observations continue to support a chaotic cold accretion scenario, where turbulence-driven condensation fuels the AGN at rates exceeding Bondi accretion, sustaining a self-regulated feedback cycle that repeatedly shapes the core of Abell 2597.