First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

By K. Akiyama, A. Alberdi, W. Alef, K. Asada, R. Azulay, A. Baczko, D. Ball, M. Baloković, J. Barrett, D. Bintley and 211 more. Astrophysical Journal, 2019

1,340 citations recorded by the source corpus.

The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ed6332a0a0cf83f0d9e3b1cd960956b68bd565d8

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Citations in the corpus

Silhouette of M87*: A new window to peek into the world of hidden dimensions (2019, methodology): “The observed shadow of M87* has an angular diameter of (42±3) μas, while it exhibits an axis ratio < 4/3 and the deviation from circularity is reportedly less than 10% [4,8,9].”
Lensing by Kerr black holes (2019, methodology): “[16] obtained a formula for the asymptotic demagnification factor as a function of black hole spin and observer inclination, confirmed the typical brightness enhancement and multi-peak structure in state-of-the-art models [5] ray-traced at higher resolution than previously considered, and proposed a”
Measurement of the spin of the M87 black hole from its observed twisted light (2019, methodology): “The deterministic part represents the slow temporal evolution of M87*, which is a quasi-static source (EHT Collaboration 2019e,f,g), when observed in the intervals of one day that separate the acquisitions of each of the two pairs of nights (5–6 April and 10–11 April) with a broad consistency.”