First Sagittarius A* Event Horizon Telescope results. V. Testing astrophysical models of the Galactic center black hole
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Date
Authors
Akiyama, Kazunori
Alberdi, Antxon
Algaba, Juan Carlos
Anantua, Richard
Asada, Keiichi
Azulay, Rebecca
Bach, Uwe
Azulay, Rebecca
Bach, Uwe
Baczko, Anne-Kathrin
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing
Abstract
In this paper we provide a first physical interpretation for the Event Horizon Telescopeʼs (EHT) 2017 observations of
Sgr A*
. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from
radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic
magnetohydrodynamics simulations, including aligned, tilted, and stellar-wind-fed simulations; radiative transfer is
performed assuming both thermal and nonthermal electron distribution functions. We test the models against 11
constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2 μm, and in the X-ray. All models fail at least
one constraint. Light-curve variability provides a particularly severe constraint, failing nearly all strongly magnetized
(magnetically arrested disk (MAD)) models and a large fraction of weakly magnetized models. A number of models fail
only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination
i 30°. They have accretion rate (5.2–9.5) × 10−9 Me yr−1
, bolometric luminosity (6.8–9.2) × 1035 erg s−1
, and
outflow power (1.3–4.8) × 1038 erg s−1
. We also find that all models with i 70° fail at least two constraints, as do all
models with equal ion and electron temperature; exploratory, nonthermal model sets tend to have higher 2.2 μm flux
density; and the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung
overproduction. Finally, we discuss physical and numerical limitations of the models, highlighting the possible
importance of kinetic effects and duration of the simulations
Description
Keywords
Black holes, Black hole physics, Galactic center, Event Horizon Telescope (EHT), Sagittarius A* (Sgr A*), Supermassive black hole
Sustainable Development Goals
Citation
Akiyama, K., Alberdi, A., Alef, W. et al. 2022, 'First Sagittarius A* Event Horizon Telescope results. V. Testing astrophysical models of the Galactic center black hole', The Astrophysical Journal Letters, vol. 930, no. 2, art. L16, pp. 1-49, doi : 10.3847/2041-8213/ac6672.