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CRA Cosmic Coffee: KwangHo Park
February 27, 2019 @ 3:00 pm - 4:00 pm
Title: Intermittent AGN feedback in galaxy clusters driven by cold gas accretion
Abstract: Recent observations of cool core clusters provide evidence that the presence of cold, atomic and molecular gas in their centers is more common than previously expected. This finding has important implications for the fueling of and feedback from the supermassive black holes (SMBHs) located in central cluster galaxies. Motivated by it, we run a suite of 2D and 3D hydrodynamic simulations to study the efficiency of radio-mode feedback driven by intermittent accretion of cold gas on the central SMBH. This type of fueling drives strong and recurrent AGN feedback episodes, whose duty cycle is determined by the presence of cold gas in the vicinity of the central SMBH. We find that intermittent AGN jets, with duty cycles shorter than the gas cooling time scale at the central region, are considerably more effective in suppressing the cooling flow than steady jets, the power of which does not significantly vary over time. Based on this, we suggest that the increased effectiveness of AGN feedback is a natural consequence of intermittency driven by accretion of cold gas, and thus this effect plays an important role in preventing runaway cooling in galaxy clusters.