@article{1639215,
  author = {Lia Medeiros and Chi-Kwan Chan and Ramesh Narayan and Feryal {\"O}zel and Dimitrios Psaltis},
  title = {Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination},
  abstract = {The 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{\textdegree} 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.},
  year = {2022},
  journal = {The Astrophysical Journal},
  volume = {924},
  pages = {46},
  language = {eng},
}