Radiatively Inefficient Accretion Flow Models of Sgr A*

Abstract

I review radiatively inefficient accretion flow models for the 2.6 million solar mass black hole (BH) in the Galactic Center. I argue for a 'concordance model' of Sgr A*: both theory and observations suggest that hot ambient gas around the BH is accreted at a rate of order 10^{-8} solar masses/year, much less than the canonical Bondi rate. I interpret Chandra observations of Sgr A* in the context of such a model: (1) the extended 'quiescent' X-ray emission is due to thermal bremsstrahlung from gas in the vicinity of the Bondi accretion radius, and (2) the ~ ksec long X-ray flares are due to synchrotron or Inverse-Compton emission by non-thermal electrons accelerated in the inner 10 Schwarzschild radii of the accretion flow.

9 pages; to appear in Astron. Nachr., Vol. 324, No. S1 (2003), Special Supplement "The central 300 parsecs of the Milky Way", Eds. A. Cotera, H. Falcke, T. R. Geballe, S. Markoff

References in corpus (11)

• Closest Star Seen Orbiting the Supermassive Black Hole at the Centre of the Milky Way
• Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
• The Dynamical Structure of Nonradiative Black Hole Accretion Flows
• A Jet-ADAF model for Sgr A*
• The Nature of the 10 Kilosecond X-ray Flare in Sgr A*
• The Magnetorotational Instability in a Collisionless Plasma
• Circular Polarization of Radio Emission from Relativistic Jets
• An Accretion-Induced X-ray Flare in Sgr A*
• A Thermal Bremsstrahlung Model For the Quiescent X-ray Emission from Sagittarius A*
• Circular polarization from stochastic synchrotron sources
• The Magnetohydrodynamics of Convection-Dominated Accretion Flows

Cited by in corpus (65)

• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• Nuclear Activity in Nearby Galaxies
• Astrophysical gyrokinetics: kinetic and fluid turbulent cascades in magnetized weakly collisional plasmas
• Stellar Processes Near the Massive Black Hole in the Galactic Center
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• The structure of the nuclear stellar cluster of the Milky Way
• Electron Heating in Hot Accretion Flows
• Interferometric Measurements of Variable 340 GHz Linear Polarization in Sagittarius A*
• First-Principles Plasma Simulations of Black-Hole Jet Launching
• Shearing Box Simulations of the MRI in a Collisionless Plasma
• The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258
• The anti-hierarchical growth of supermassive black holes
• Nuclear Accretion in Galaxies of the Local Universe: Clues from Chandra Observations
• An X-ray survey of the 2Jy sample. I: is there an accretion mode dichotomy in radio-loud AGN?
• The two states of Sgr A* in the near-infrared: bright episodic flares on top of low-level continuous variability
• Chandra and XMM-Newton Observations of the Nucleus of Centaurus A
• Variations in the spectral slope of Sgr A* during a NIR flare
• Obscuration and Origin of Nuclear X-ray emission in FR I Radio Galaxies
• Prospects for testing the nature of Sgr A*'s NIR flares on the basis of current VLT- and future VLTI-observations
• Star Captures by Quasar Accretion Disks: A Possible Explanation of the M-sigma Relation
• Relativistic Mergers of Supermassive Black Holes and their Electromagnetic Signatures
• Active Galactic Nuclei in Void Regions
• The mean infrared emission of SagittariusA*
• The Submillimeter Polarization of Sgr A*
• Epicyclic Motions and Standing Shocks in Numerically Simulated Tilted Black-Hole Accretion Disks
• Statistics of Kinetic Dissipation in Earth's Magnetosheath -- MMS Observations
• First proper motions of thin dust filaments at the Galactic Center
• Synchrotron Radiation From Radiatively Inefficient Accretion Flow Simulations: Applications to Sgr A*
• The Link Between Star Formation and Accretion in LINERs: A Comparison with other AGN Subclasses
• Transition from collisionless to collisional MRI
• Accretion and nuclear activity of quiescent supermassive black holes. I: X-ray study
• Dependence of Kinetic Plasma Turbulence on Plasma beta
• Collisionless accretion onto black holes: dynamics and flares
• The Effects of Thermal Conduction on Radiatively-Inefficient Accretion Flows
• On the Origin of Ultraviolet Emission and the Accretion Model of Low-luminosity AGNs
• MIGHTEE: the nature of the radio-loud AGN population
• On the origin of the X-rays and the nature of accretion in NGC 4261
• Spherical Accretion with Anisotropic Thermal Conduction
• NUclei of GAlaxies: V. Radio emission in 7 NUGA sources
• Constraints on ion vs. electron heating by plasma turbulence at low beta
• Dynamical Structure of Viscous Accretion Disks with Shocks
• Particle Acceleration and the Production of Relativistic Outflows in Advection-Dominated Accretion Disks with Shocks
• AGN activity and the misaligned hot ISM in the compact radio elliptical NGC4278
• Properties of Accretion Flows Around Coalescing Supermassive Black Holes
• Positron Effects on Polarized Images and Spectra from Jet and Accretion Flow Models of M87* and Sgr A*
• A Self-Consistent Model for the Formation of Relativistic Outflows in Advection-Dominated Accretion Disks with Shocks
• Nonthermal THz to TeV Emission from Stellar Wind Shocks in the Galactic Center
• An X-ray view of WLRGs/LINERs
• Unobscured QSO2: A New Class of Objects?
• Fully kinetic large scale simulations of the collisionless Magnetorotational instability
• The millimetre variability of M81* -- Multi-epoch dual frequency mm-observations of the nucleus of M81
• Braginskii viscosity on an unstructured, moving mesh accelerated with super-time-stepping
• Pressure-anisotropy-induced nonlinearities in the kinetic magnetorotational instability
• No sign of G2's encounter affecting Sgr A*'s X-ray flaring rate from $Chandra$ observations
• A new framework for magnetohydrodynamic simulations with anisotropic pressure
• A Measurement of the Effective Mean-Free-Path of Solar Wind Protons
• Collisionless conduction in a high-beta plasma: a collision operator for whistler turbulence
• Coordinated multi-wavelength observations of Sgr A*
• Spherical Accretion in Nearby Weakly Active Galaxies
• Onset of magnetic reconnection in a collisionless, high-beta plasma
• A cool disk in the Galactic Center?
• First-principles measurement of ion and electron energization in collisionless accretion flow
• Jet Launching Radius in Low-Power Radio-Loud AGNs in Advection-Dominated Accretion Flows
• Self-similar Solution of Hot Accretion Flow with Thermal Conduction and Anisotropic Pressure
• Variability of Sagittarius A* at 3 GHz on minute-scale with MeerKAT