Rotation in Event Horizon Telescope Movies

Abstract

The Event Horizon Telescope (EHT) has produced images of M87* and Sagittarius A*, and will soon produce time sequences of images, or movies. In anticipation of this, we describe a technique to measure the rotation rate, or pattern speed ${\Omega }_p$, from movies using an autocorrelation technique. We validate the technique on Gaussian random field models with a known rotation rate and apply it to a library of synthetic images of Sgr A* based on general relativistic magnetohydrodynamics simulations. We predict that EHT movies will have ${\Omega }_p\approx 1^{\circ }$ per $GM{c}^{-3}$, which is of order $15\%$ of the Keplerian orbital frequency in the emitting region. We can plausibly attribute the slow rotation seen in our models to the pattern speed of inward-propagating spiral shocks. We also find that ${\Omega }_p$ depends strongly on inclination. Application of this technique will enable us to compare future EHT movies with the clockwise rotation of Sgr A* seen in near-infrared flares by GRAVITY. Pattern speed analysis of future EHT observations of M87* and Sgr A* may also provide novel constraints on black hole inclination and spin, as well as an independent measurement of black hole mass.

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• Polarimetric signatures of hot spots in black hole accretion flows
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Cited by in corpus (9)

• Fitting the light curves of Sagittarius A* with a hot-spot model
• Hot-spots around Sagittarius A*: Joint fits to astrometry and polarimetry
• Chaotic magnetic disconnections trigger flux eruptions in accretion flows channeled onto magnetically saturated Kerr black holes
• Explanation for the absence of secondary peaks in black hole light curve autocorrelations
• Deep learning inference with the Event Horizon Telescope II. The Zingularity framework for Bayesian artificial neural networks
• Electron Heating in the Trans-Relativistic Perpendicular Shocks of Tilted Accretion Flows
• Assessing the Role of Intrinsic Variability in Black Hole Parameter Inference using Multi-Epoch EHT Data
• Auto- and cross-correlations for multiple images of corotating hotspots in accretion disks
• Extreme-Lensing Signatures Revealed by Correlations of Simulated Black-Hole Movies