MEASURING THE DIRECTION AND ANGULAR VELOCITY OF A BLACK HOLE ACCRETION DISK VIA LAGGED INTERFEROMETRIC COVARIANCE
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Johnson-2015-MEASURING THE DIRECT.pdf
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Author(s)
Johnson, Michael D.
Loeb, Abraham
Shiokawa, Hotaka
Chael, Andrew A.
Doeleman, Sheperd Samuel
Date Issued
November 2015
Journal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Johnson, Michael D., Abraham Loeb, Hotaka Shiokawa, Andrew A. Chael, and Sheperd S. Doeleman. “MEASURING THE DIRECTION AND ANGULAR VELOCITY OF A BLACK HOLE ACCRETION DISK VIA LAGGED INTERFEROMETRIC COVARIANCE.” The Astrophysical Journal 813, no. 2 (November 5, 2015): 132. © 2015 The American Astronomical Society
Version
Final published version
Abstract
We show that interferometry can be applied to study irregular, rapidly rotating structures, as are expected in the turbulent accretion flow near a black hole. Specifically, we analyze the lagged covariance between interferometric baselines of similar lengths but slightly different orientations. For a flow viewed close to face-on, we demonstrate that the peak in the lagged covariance indicates the direction and angular velocity of the emission pattern from the flow. Even for moderately inclined flows, the covariance robustly estimates the flow direction, although the estimated angular velocity can be significantly biased. Importantly, measuring the direction of the flow as clockwise or counterclockwise on the sky breaks a degeneracy in accretion disk inclinations when analyzing time-averaged images alone. We explore the potential efficacy of our technique using three-dimensional, general relativistic magnetohydrodynamic simulations, and we highlight several baseline pairs for the Event Horizon Telescope (EHT) that are well-suited to this application. These results indicate that the EHT may be capable of estimating the direction and angular velocity of the emitting material near Sgr A*, and they suggest that a rotating flow may even be utilized to improve imaging capabilities.
MIT Department
Haystack Observatory
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DOI of Published Version
https://doi.org/10.1088/0004-637x/813/2/132
