Numerical Models of Sgr A*

TL;DR

This paper reviews general relativistic magnetohydrodynamic simulations of Sgr A*, combining radiative transfer and ray tracing to model spectra and images, constraining black hole spin, temperature ratios, and inclination.

Contribution

It introduces a comprehensive modeling approach integrating MHD simulations with radiative transfer and image analysis to better understand Sgr A*'s properties.

Findings

High black hole spin ($a_* oughly 0.9$)

Electron temperatures near ion temperatures ($T_i/T_e oughly 3$)

High inclination angles ($i oughly 90^ extdegree$)

Abstract

We review results from general relativistic axisymmetric magnetohydrodynamic simulations of accretion in Sgr A*. We use general relativistic radiative transfer methods and to produce a broad band (from millimeter to gamma-rays) spectrum. Using a ray tracing scheme we also model images of Sgr A* and compare the size of image to the VLBI observations at 230 GHz. We perform a parameter survey and study radiative properties of the flow models for various black hole spins, ion to electron temperature ratios, and inclinations. We scale our models to reconstruct the flux and the spectral slope around 230 GHz. The combination of Monte Carlo spectral energy distribution calculations and 230 GHz image modeling constrains the parameter space of the numerical models. Our models suggest rather high black hole spin ($a_*\approx 0.9$), electron temperatures close to the ion temperature ($T_i/T_e \sim 3$) and high inclination angles ($i \approx 90 \deg$).