Spectral and Imaging properties of Sgr A* from High-Resolution 3D GRMHD Simulations with Radiative Cooling

Abstract

The candidate supermassive black hole in the Galactic Centre, Sagittarius A* (Sgr A*), is known to be fed by a radiatively inefficient accretion flow (RIAF), inferred by its low accretion rate. Consequently, radiative cooling has in general been overlooked in the study of Sgr A*. However, the radiative properties of the plasma in RIAFs are poorly understood. In this work, using full 3D general-relativistic magneto-hydrodynamical simulations, we study the impact of radiative cooling on the dynamical evolution of the accreting plasma, presenting spectral energy distributions and synthetic sub-millimeter images generated from the accretion flow around Sgr A*. These simulations solve the approximated equations for radiative cooling processes self-consistently, including synchrotron, bremsstrahlung, and inverse Compton processes. We find that radiative cooling plays an increasingly important role in the dynamics of the accretion flow as the accretion rate increases: the mid-plane density grows and the infalling gas is less turbulent as cooling becomes stronger. The changes in the dynamical evolution become important when the accretion rate is larger than $10^{-8}{M}_{\odot }{\mathrm{yr}}^{-1}$ ($\gtrsim 10^{-7}{\dot{M}}_{\mathrm{Edd}}$, where ${\dot{M}}_{\mathrm{Edd}}$ is the Eddington accretion rate). The resulting spectra in the cooled models also differ from those in the non-cooled models: the overall flux, including the peak values at the sub-mm and the far-UV, is slightly lower as a consequence of a decrease in the electron temperature. Our results suggest that radiative cooling should be carefully taken into account in modelling Sgr A* and other low-luminosity active galactic nuclei that have a mass accretion rate of $\dot{M}>10^{-7}{\dot{M}}_{\mathrm{Edd}}$.

16 pages, 16 figures, accepted for publication in MNRAS

References in corpus (21)

• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• An Update on Monitoring Stellar Orbits in the Galactic Center
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• An Improved Distance and Mass Estimate for Sgr A* from a Multistar Orbit Analysis
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• Global simulations of axisymmetric radiative black hole accretion disks in general relativity with a sub-grid magnetic dynamo
• Simulating the Emission and Outflows from Accretion Disks
• Observational appearance of inefficient accretion flows and jets in 3D GRMHD simulations: Application to Sgr~A*
• A Constant Spectral Index for Sagittarius A* During Infrared/X-ray Intensity Variations
• The Disc-Jet Symbiosis Emerges: Modeling the Emission of Sagittarius A* with Electron Thermodynamics
• A polarised infrared flare from Sagittarius A* and the signatures of orbiting plasma hotspots
• Ab Initio Horizon-Scale Simulations of Magnetically Arrested Accretion in Sagittarius A* Fed by Stellar Winds
• Sgr A* near-infrared flares from reconnection events in a magnetically arrested disc
• How to hide large scale outflows: size constraints on the jets of Sgr A*
• Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. I. Compression-Driven Instabilities and the Electron Heating Mechanism
• Imaging an Event Horizon: submm-VLBI of a Super Massive Black Hole
• On the Comparison of AGN with GRMHD Simulations: I. Sgr A*
• Modelling the black hole silhouette in Sgr A* with ion tori
• Accretion of Low Angular Momentum Material onto Black Holes: Radiation Properties of Axisymmetric MHD Flows

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• Survey of Radiative, Two-Temperature Magnetically Arrested Simulations of the Black Hole M87* I: Turbulent Electron Heating
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