RADIATIVE MODELS OF SGR A* FROM GRMHD SIMULATIONS

By M. Mościbrodzka, Charles F. Gammie, Joshua C. Dolence, H. Shiokawa, P. Leung. 2009

230 citations recorded by the source corpus.

Using flow models based on axisymmetric general relativistic magnetohydrodynamics simulations, we construct radiative models for Sgr A*. Spectral energy distributions (SEDs) that include the effects of thermal synchrotron emission and absorption, and Compton scattering, are calculated using a Monte Carlo technique. Images are calculated using a ray-tracing scheme. All models are scaled so that the 230 GHz flux density is 3.4 Jy. The key model parameters are the dimensionless black hole spin a*, the inclination i, and the ion-to-electron temperature ratio Ti/Te. We find that (1) models with Ti/Te = 1 are inconsistent with the observed submillimeter spectral slope; (2) the X-ray flux is a strongly increasing function of a*; (3) the X-ray flux is a strongly increasing function of i; (4) 230 GHz image size is a complicated function of i, a*, and Ti/Te, but the Ti/Te = 10 models are generally large and at most marginally consistent with the 230 GHz very long baseline interferometry (VLBI) data; (5) for models with Ti/Te = 10 and i = 85° the event horizon is cloaked behind a synchrotron photosphere at 230 GHz and will not be seen by VLBI, but these models overproduce near-infrared and X-ray flux; (6) in all models whose SEDs are consistent with observations, the event horizon is uncloaked at 230 GHz; (7) the models that are most consistent with the observations have a* ∼ 0.9. We finish with a discussion of the limitations of our model and prospects for future improvements.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/25cd7b1c96311c1d5fdeb8f8df2192e5f663f217

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Citations in the corpus

EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A* (2010, methodology): “Since that time a number of groups have analyzed the 2007 mm-VLBI data using various physically motivated accretion models for the emission region (Broderick et al. 2009; Huang et al. 2009; Móscibrodzka et al. 2009; Dexter et al. 2010), inferring from these efforts the black hole spin vector.”
A public code for general relativistic, polarised radiative transfer around spinning black holes (2016, methodology): “Snapshots from these simulations have been used as models of Sgr A* (e.g., Noble et al. 2007; Mościbrodzka et al. 2009).”
Electron Thermodynamics in GRMHD Simulations of Low-Luminosity Black Hole Accretion (2015, methodology): “…find that the resulting electron temperatures differ significantly from the assumption of a constant electron to proton temperature ratio used in previous work to predict the emission from GRMHD simulations (Mościbrodzka et al. 2009; Dibi et al. 2012; Drappeau et al. 2013); see, e.g. Figures9-11.”
Hot Accretion Flows Around Black Holes (2014, methodology): “…model (Huang et al. 2007, Broderick et al. 2011) and in numerous studies based on MHD simulations (Goldston et al. 2005; Noble et al. 2007; Sharma et al. 2007b, 2008; Mościbrodzka et al. 2009; Chan et al. 2009; Kato et al. 2009; Dexter et al. 2010; Shcherbakov et al. 2012; Dexter & Fragile 2013).”
THE SUBMILLIMETER BUMP IN Sgr A* FROM RELATIVISTIC MHD SIMULATIONS (2010, methodology): “We follow Goldston et al. (2005); Mościbrodzka et al. (2009) and generate images using two-temperature models with constant ratios of Ti/Te, which is then another free parameter.”
Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA* (2018, background): “Theoretical estimates of the magnetic field in the innermost accretion zone around SgrA* vary between 5 and 100 G (Yuan et al. 2003; Mościbrodzka et al. 2009; Dodds-Eden et al. 2010; Dexter et al. 2010; Ponti et al. 2017).”
PHOTON RINGS AROUND KERR AND KERR-LIKE BLACK HOLES (2013, methodology): “Mościbrodzka et al. (2009) and Dexter et al. (2009, 2010) fitted the VLBI and spectral data to sets of images obtained from three-dimensional general-relativistic magnetohydrodynamic (3D-GRMHD) simulations (Gammie et al. 2003; Fragile et al. 2007, 2009; McKinney & Blandford 2009).”
General relativistic magnetohydrodynamical simulations of the jet in M 87 (2015, methodology): “8 the middle 1 The emission from an accretion disk will also produce crescentlike images whenRhigh is relatively low, see Appendix or, e.g., Mościbrodzka et al. 2009, Mościbrodzka et al. 2014, and Dexter et al. 2012.”
TESTING THE NO-HAIR THEOREM WITH OBSERVATIONS IN THE ELECTROMAGNETIC SPECTRUM. II. BLACK HOLE IMAGES (2010, background): “5 in Mościbrodzka et al. 2009; panels 1 and 3 in Fig.”
On the charge of the Galactic centre black hole (2018, methodology): “…and the proton (ion) temperatures differ, the proton temperature is larger than the electron temperature by about a factor of ' 1− 5, Te/Tp ≥ 1/5 (Mościbrodzka et al. 2009; Dexter et al. 2010), which gives the lower limit to the excess of the positive charge in the range of influence of…”
The size of the jet launching region in M87 (2011, methodology): “This is many more free parameters than in prior radiative models of Sgr A* from GRMHD simulations (Mościbrodzka et al. 2009; Dexter, Agol & Fragile 2009; Dexter et al. 2010; Shcherbakov, Penna & McKinney 2010).”