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  1. Abstract

    The inner few parsecs of the Milky Way’s Galactic center contain the central accreting supermassive black hole, over a million stars, and multiple large gaseous structures. In the past, the structures at these length scales have generally been modeled independently of each other. It is consequently not well understood how these complex features interact with each other, nor how gas flows between the outer few parsecs and the inner subarcsecond region (1″ ≈ 0.04 pc). In this work, we present hydrodynamic simulations of the inner few parsecs of the Galactic center that, for the first time, combine a realistic treatment of stellar winds and the circumnuclear disk (CND) as they interact with the gravitational potential of the nuclear star cluster and Sagittarius A*. We observe interactions of the stellar winds with the inner edge of the CND, which leads to the growth of instabilities, induced accretion of cool gas from the inner edge of the disk, and the eventual formation of a small accretion disk of ∼104–105K withinr∼ 0.1 pc. The formation of an inner disk qualitatively agrees with observations. This disk grows in radial extent and mass with time on ≳10 kyr timescales, with a growth rate ofMtkyr3.5. We discuss additional physical mechanisms not yet included in this work that can improve our model.

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    We study the observational signatures of magnetically arrested black hole accretion with non-rotating inflow on to a rotating black hole; we consider a range of angles between the black hole spin and the initial magnetic field orientation. We compare the results of our general relativistic magneto-hydrodynamic simulations to more commonly used rotating initial conditions and to the Event Horizon Telescope (EHT) observations of M87. We find that the mm intensity images, polarization images, and synchrotron emission spectra are very similar among the different simulations when post-processed with the same electron temperature model; observational differences due to different electron temperature models are significantly larger than those due to the different realizations of magnetically arrested accretion. The orientation of the mm synchrotron polarization is particularly insensitive to the initial magnetic field orientation, the electron temperature model, and the rotation of the inflowing plasma. The largest difference among the simulations with different initial rotation and magnetic tilt is in the strength and stability of the jet; spherical inflow leads to kink-unstable jets. We discuss the implications of our results for current and future EHT observations and for theoretical models of event-horizon-scale black hole accretion.

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