Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination
AffiliationSteward Observatory, Department of Astronomy, University of Arizona
Data Science Institute, University of Arizona
Program in Applied Mathematics, University of Arizona
MetadataShow full item record
PublisherAmerican Astronomical Society
CitationMedeiros, L., Chan, C.-K., Narayan, R., Ozel, F., & Psaltis, D. (2022). Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination. Astrophysical Journal.
RightsCopyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.
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AbstractThe Event Horizon Telescope recently captured images of the supermassive black hole in the center of the M87 galaxy, which shows a ring-like emission structure with the south side only slightly brighter than the north side. This relatively weak asymmetry in the brightness profile along the ring has been interpreted as a consequence of the low inclination of the observer (around 17° for M87), which suppresses the Doppler beaming and boosting effects that might otherwise be expected due to the nearly relativistic velocities of the orbiting plasma. In this work, we use a large suite of general relativistic magnetohydrodynamic simulations to reassess the validity of this argument. By constructing explicit counterexamples, we show that low inclination is a sufficient but not necessary condition for images to have low brightness asymmetry. Accretion flow models with high accumulated magnetic flux close to the black hole horizon (the so-called magnetically arrested disks) and low black hole spins have angular velocities that are substantially smaller than the orbital velocities of test particles at the same location. As a result, such models can produce images with low brightness asymmetry even when viewed edge on. © 2022. The Author(s). Published by the American Astronomical Society..
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Except where otherwise noted, this item's license is described as Copyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.