Bogdán, Ákos, van Weeren, Reinout J., Kraft, Ralph P., Forman, William R., Randall, Scott W., Giacintucci, Simona, Churazov, Eugene, O'Dea, Christopher P., Baum, Stefi A., Noell-Storr, Jacob, and Jones, Christine. 2014. "Young AGN Outburst Running over Older X-Ray Cavities." Astrophysical Journal Letters 782:L19. https://doi.org/10.1088/2041-8205/782/2/L19
Although the energetic feedback from active galactic nuclei (AGNs) is believed to have a profound effect on the evolution of galaxies and clusters of galaxies, details of AGN heating remain elusive. Here, we study NGC 193-a nearby lenticular galaxy-based on X-ray (Chandra) and radio (Very Large Array and Giant Meter-wave Radio Telescope) observations. These data reveal the complex AGN outburst history of the galaxy: we detect a pair of inner X-ray cavities, an outer X-ray cavity, a shock front, and radio lobes extending beyond the inner cavities. We suggest that the inner cavities were produced ~78 Myr ago by a weaker AGN outburst, while the outer cavity, the radio lobes, and the shock front are due to a younger (13-26 Myr) and 4-8 times more powerful outburst. Combining this with the observed morphology of NGC 193, we conclude that NGC 193 likely represents the first example of a second, more powerful, AGN outburst overrunning an older, weaker outburst. These results help us to understand how the outburst energy is dissipated uniformly in the core of galaxies, and therefore may play a crucial role in resolving how AGN outbursts suppress the formation of large cooling flows at cluster centers.