Probing the High-frequency Variability of NGC 5044: The Key to Active Galactic Nucleus Feedback

Abstract The active galactic nucleus (AGN) feeding and feedback process in the centers of galaxy clusters and groups is still not well understood. NGC 5044 is the ideal system in which to study AGN feedback. It hosts the largest known reservoir of cold gas in any cool-core galaxy group, and features several past epochs of AGN feedback imprinted as cavities in the X-ray-bright intragroup medium, as well as parsec-scale jets. We present Submillimeter Array, Karl G. Jansky Very Large Array, James Clerk Maxwell Telescope, and Atacama Large Millimeter/submillimeter Array high-frequency observations of NGC 5044 to assess the time variability of the millimeter-wave band emission from the accretion disk, and quantify the spectral energy distribution (SED) from the radio to submillimeter band. The SED is well described by an advection-dominated accretion flow (ADAF) model and self-absorbed jet emission from an aging plasma with τ ∼ 1 kyr. We find a characteristic variability timescale of 150 days, which constrains the ADAF emission region to about 0.1 pc, and the magnetic field to ∼4.7 mG in the jets and 870 G in the accretion disk. Longer monitoring/sampling will allow to understand if the underlying process is truly periodic in nature.