Isotropic Active Galactic Nucleus Heating with Small Radio-quiet Bubbles in the NGC 5044 Group

A Chandra observation of the X-ray bright group NGC 5044 shows that the X-ray emitting gas has been strongly perturbed by recent outbursts from the central active galactic nucleus (AGN) and also by motion of the central dominant galaxy relative to the group gas. The NGC 5044 group hosts many small radio-quiet cavities with a nearly isotropic distribution, cool filaments, a semi-circular cold front, and a two-armed spiral shaped feature of cool gas. A Giant Metrewave Radio Telescope (GMRT) observation of NGC 5044 at 610 MHz shows the presence of extended radio emission with a "torus-shaped" morphology. The largest X-ray filament appears to thread the radio torus, suggesting that the lower entropy gas within the filament is material being uplifted from the center of the group. The radio emission at 235 MHz is much more extended than the emission at 610 MHz, with little overlap between the two frequencies. One component of the 235 MHz emission passes through the largest X-ray cavity and is then deflected just behind the cold front. A second detached radio lobe is also detected at 235 MHz beyond the cold front. All of the smaller X-ray cavities in the center of NGC 5044 are undetected in the GMRT observations. Since the smaller bubbles are probably no longer momentum driven by the central AGN, their motion will be affected by the group "weather" as they buoyantly rise outward. Hence, most of the enthalpy within the smaller bubbles will likely be deposited near the group center and isotropized by the group weather. The total mechanical power of the smaller radio quiet cavities is P_c = 9.2 × 10⁴¹ erg s^-1 which is sufficient to suppress about one-half of the total radiative cooling within the central 10 kpc. This is consistent with the presence of Hα emission within this region which shows that at least some of the gas is able to cool. The mechanical heating power of the larger southern cavity, located between 10 and 20 kpc, is six times greater than the combined mechanical power of the smaller radio-quiet cavities and could suppress all radiative cooling within the central 25 kpc if the energy were deposited and isotropized within this region. Within the central 20 kpc, emission from low-mass X-ray binaries (LMXBs) is a significant component of the X-ray emission above 2 keV. The presence of hard X-ray emission from unresolved LMXBs makes it difficult to place strong constraints on the amount of shock heated gas within the X-ray cavities.