Discovery of a Powerful >1061 erg AGN outburst in the Distant Galaxy Cluster SPT-CL J0528-5300

We present ~103 ks of Chandra observations of the galaxy cluster SPT-CL J0528-5300 (SPT0528, z = 0.768). This cluster harbors the most radio-loud (L_{1.4 GHz} = 1.01x10³³ erg s^-1 Hz^-1) central AGN of any cluster in the South Pole Telescope (SPT) SZ survey with available X-ray data. We find evidence of AGN-inflated cavities in the X-ray emission, which are consistent with the orientation of the jet direction revealed by ATCA radio data. At >10⁶¹ erg, the outburst in SPT0528 is among the most energetic known in the universe, and certainly the most powerful known at z >0.25. This work demonstrates that such powerful outbursts can be detected even in shallow X-ray exposures out to relatively high redshifts (z~0.8), providing an avenue for studying the evolution of extreme AGN feedback. The ratio of the cavity power (P_cav = 6.1±3.4 x10⁴⁵ erg s^-1) to the cooling luminosity (L_cool = 1.5±0.5x10⁴⁴ erg s^-1) for SPT0528 is among the highest measured to date. If, in the future, additional systems are discovered at similar redshifts with equally high P_cav/L_cool ratios, it would imply that the feedback/cooling cycle was not as gentle at high redshifts as in the low-redshift universe.