The Effects of Thermal Conduction on Radiatively Inefficient Accretion Flows

Johnson, Bryan M.; Quataert, Eliot

doi:10.1086/513065

Cited by 53 publications

(76 citation statements)

References 45 publications

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“…No heat is transferred via conduction across magnetic field lines, but the effective conductivity is still high in the turbulent flows as proposed theoretically (Narayan & Medvedev 2001) and confirmed with numerical simulations (Parrish et al 2010). The action of conduction helps to explain the shallow density slope of the Sgr A * accretion flow (Johnson & Quataert 2007;Shcherbakov & Baganoff 2010).…”

Section: Conduction and Small-scale Feedbacksupporting

confidence: 57%

“…We find the shallow density profile n ∝ r −β with β ≈ 1 across a large range of scales in the NGC 3115 nucleus. As briefly discussed in Section 3.1, the shallow density profile commonly occurs in CDAFs (Quataert & Gruzinov 2000;Narayan et al 2000), in the accretion flows with conduction (Johnson & Quataert 2007;Shcherbakov & Baganoff 2010), and in the accretion flows with the outflows above and below the midplane (Blandford & Begelman 1999;Yuan et al 2003Yuan et al , 2012b. However, there are other reasons to have β ≈ 1 near the Bondi radius in the hot gas flows.…”

Section: What Does the Density Slope Mean?mentioning

confidence: 98%

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

Shcherbakov

Wong

Irwin

et al. 2014

ApJ

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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.

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Section: Conduction and Small-scale Feedbacksupporting

confidence: 57%

Section: What Does the Density Slope Mean?mentioning

confidence: 98%

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

Shcherbakov

Wong

Irwin

et al. 2014

ApJ

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“…This neglects, however, several physical processes that have different effects on the electron and proton thermodynamics and that are currently only included in onedimensional semi-analytic models. Such effects include electron thermal conduction (e.g., Johnson & Quataert 2007), electron cooling (e.g., Narayan & Yi 1995), and non-thermal particle acceleration and emission (e.g., Yuan, Quataert & Narayan 2003). To date, extensions of the simple T p /T e = const.…”

Section: Introductionmentioning

confidence: 99%

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

172

242

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Simple assumptions made regarding electron thermodynamics often limit the extent to which general relativistic magnetohydrodynamic (GRMHD) simulations can be applied to observations of low-luminosity accreting black holes. We present, implement, and test a model that self-consistently evolves an entropy equation for the electrons and takes into account the effects of spatially varying electron heating and relativistic anisotropic thermal conduction along magnetic field lines. We neglect the back-reaction of electron pressure on the dynamics of the accretion flow. Our model is appropriate for systems accreting at ≪ 10 −5 of the Eddington accretion rate, so radiative cooling by electrons can be neglected. It can be extended to higher accretion rates in the future by including electron cooling and proton-electron Coulomb collisions. We present a suite of tests showing that our method recovers the correct solution for electron heating under a range of circumstances, including strong shocks and driven turbulence. Our initial applications to axisymmetric simulations of accreting black holes show that (1) physically-motivated electron heating rates that depend on the local magnetic field strength yield electron temperature distributions significantly different from the constant electron to proton temperature ratios assumed in previous work, with higher electron temperatures concentrated in the coronal region between the disc and the jet; (2) electron thermal conduction significantly modifies the electron temperature in the inner regions of black hole accretion flows if the effective electron mean free path is larger than the local scale-height of the disc (at least for the initial conditions and magnetic field configurations we study). The methods developed in this work are important for producing more realistic predictions for the emission from accreting black holes such as Sagittarius A* and M87; these applications will be explored in future work.

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“…A significant theoretical uncertainty in modeling SgrA * is that such weakly collisional flows involve kinetic physics with undetermined heating rates (Quataert & Gruzinov 1999;Sharma et al 2006;Johnson & Quataert 2007;Howes et al 2008;Riquelme et al 2012Riquelme et al , 2015 for a population of thermal or non-thermal electrons (Mahadevan & Quataert 1997;Özel et al 2000;Yuan et al 2003;Lynn et al 2014) not fully accounted for in GRMHD simulations. For example, the jet might light up only if actually launched under favorable physical conditions, or the jet could be always present but the particle heating could control whether the jet lights up.…”

Section: Introductionmentioning

confidence: 99%

Probing the Magnetic Field Structure in on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations

Gold

McKinney

Johnson

et al. 2017

ApJ

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Magnetic fields are believed to drive accretion and relativistic jets in black hole accretion systems, but the magnetic field structure that controls these phenomena remains uncertain. We perform general relativistic (GR) polarized radiative transfer of time-dependent three-dimensional GR magnetohydrodynamical simulations to model thermal synchrotron emission from the Galactic Center source SagittariusA * (SgrA * ). We compare our results to new polarimetry measurements by the Event Horizon Telescope (EHT) and show how polarization in the visibility (Fourier) domain distinguishes and constrains accretion flow models with different magnetic field structures. These include models with small-scale fields in disks driven by the magnetorotational instability as well as models with large-scale ordered fields in magnetically arrested disks. We also consider different electron temperature and jet mass-loading prescriptions that control the brightness of the disk, funnel-wall jet, and Blandford-Znajek-driven funnel jet. Our comparisons between the simulations and observations favor models with ordered magnetic fields near the black hole event horizon in SgrA * , though both disk-and jet-dominated emission can satisfactorily explain most of the current EHT data. We also discuss how the black hole shadow can be filled-in by jet emission or mimicked by the absence of funnel jet emission. We show that stronger model constraints should be possible with upcoming circular polarization and higher frequency (349 GHz) measurements.

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The Effects of Thermal Conduction on Radiatively Inefficient Accretion Flows

Cited by 53 publications

References 45 publications

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

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

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Probing the Magnetic Field Structure in on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations

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