Modeling Hot Gas Flow in the Low-Luminosity Active Galactic Nucleus of NGC 3115

Abstract

Based on the dynamical black hole (BH) mass estimates, NGC 3115 hosts the closest billion solar mass BH. Deep studies of the center revealed a very underluminous active galactic nucleus (AGN) immersed in an old massive nuclear star cluster. Recent 1 Ms Chandra X-ray visionary project observations of the NGC 3115 nucleus resolved hot tenuous gas, which fuels the AGN. In this paper we connect the processes in the nuclear star cluster with the feeding of the supermassive BH. We model the hot gas flow sustained by the injection of matter and energy from the stars and supernova explosions. We incorporate electron heat conduction as the small-scale feedback mechanism, the gravitational pull of the stellar mass, cooling, and Coulomb collisions. Fitting simulated X-ray emission to the spatially and spectrally resolved observed data, we find the best-fitting solutions with χ 2 /dof = 1.00 for dof = 236 both with and without conduction. The radial modeling favors a low BH mass <1.3 × 10 9 M . The best-fitting supernova rate and the best-fitting mass injection rate are consistent with their expected values. The stagnation point is at r st 1 , so that most of the gas, including the gas at a Bondi radius r B = 2 -4 , outflows from the region. We put an upper limit on the accretion rate at 2 × 10 −3 M yr −1 . We find a shallow density profile n ∝ r −β with β ≈ 1 over a large dynamic range. This density profile is determined in the feeding region 0. 5-10 as an interplay of four processes and effects: (1) the radius-dependent mass injection, (2) the effect of the galactic gravitational potential, (3) the accretion flow onset at r 1 , and (4) the outflow at r 1 . The gas temperature is close to the virial temperature T v at any radius.

Multiphase environment of compact galactic nuclei: the role of the nuclear star cluster

“…tified since several studies of spherical hot accretion onto Galactic Center show that a two-temperature plasma develops only within the innermost tens of gravitational radii (<0.1 arcsec) from the black hole (Moscibrodzka 2006;Mościbrodzka et al 2009;Shcherbakov et al 2014). In addition, strong arguments in favour of very efficient electron-ion coupling (Bisnovatyi-Kogan & Lovelace 1997) imply that this region is very small.…”

Circumnuclear media of quiescent supermassive black holes

“…The high value of v Ia w implies that Ia SNe represent an important source of CNM heating. However, SNe can only be approximated as supplying heating which is spatially and temporally homogeneous if the rate of SNe is rapid compared to the characteristic evolution time of the flow at the radius of interest (Shcherbakov et al 2014). We define the "Ia radius"…”

“…Another approach to determine the inflow rates, which we adopt in this paper, is to directly calculate the density, velocity and temperature profiles of the CNM using a physically motivated hydrodynamic model. Mass is injected into the nuclear environment via stellar winds, while energy is input from several sources including stellar winds, supernovae (SNe), and AGN feedback (Quataert 2004;De Colle et al 2012;Shcherbakov et al 2014). Unlike previous works, which focused primarily on modeling individual galaxies, here we model the CNM properties across a representative range of galaxy properties, including different SMBH masses, stellar density profiles, and star formation histories (SFHs).…”

Hot Gas Flows on Parsec Scale in the Low-Luminosity Active Galactic Nucleus NGC 3115

“…Moreover, thermal conduction is also incorporated since it should play an important role in collisionless plasma such as the RIAF with low accretion rate (Johnson & Quataert 2007). Shcherbakov et al (2014) highlights its effect but we think it is overestimated as discussed below. The details of our physics are given as follows.…”

“…In other words, the gravitational potential contributed by stars as well as the stellar winds and supernovae as mass and energy sources might be important. Indeed, by considering the existence of stars, Shcherbakov et al (2014) perform one-dimensional calculations on the case of NGC 3115 and can roughly fit the data. However, their models still have a variety of limitations owing to one-dimension as they have already pointed out at the end of their paper.…”