Modeling the Accretion Flow Onset in the Low-Luminosity Active Galactic Nucleus of NGC3115
Abstract
The superb angular resolution of the Chandra satellite allows us to probe accretion flows in AGNs on scales comparable to the radius of the black hole (BH) gravitational influence (the "Bondi radius"). X-ray emission from the onset region of the accretion flow has recently been seen in a 1Ms X-ray visionary project (XVP) observation of NGC3115. I discuss the theoretical modeling of those data with the inflow-outflow solution of gas dynamics. The BH is fed by stellar winds, most of which outflow from the region, while a small fraction settles into a radiatively inefficient accretion flow (RIAF). The galactic potential, line cooling, and small-scale feedback via conduction all influence the behavior of the gas. The X-ray emission of modeled tenuous gas is computed based on ATOMDB 2.0. The set of radius-dependent hot plasma X-ray spectra is combined with contributions from unresolved point sources to fit the observations. A good joint fit to the observed radius-dependent spectra is readily found for a realistic model which includes all relevant physics. All projection effects are self-consistently taken into account in the radiation modeling. The observations combined with theoretical modeling illuminate the intricate process of AGN feeding at low luminosity, help to constraint the accretion rate and the BH mass, and provide useful insights into feeding of more powerful AGNs. The accretion rate in models with small-scale feedback is found to be much lower compared to the accretion rate in a simplistic Bondi model. Our model was previously successfully applied to Sgr A* and will be applied to a variety of other sources in the near future.
