![]() Across all methods, we measure a crescent diameter of 42 ± 3 μas and constrain its fractional width to be <0.5. We find that >50% of the total flux at arcsecond scales comes from near the horizon, and that the emission is dramatically suppressed interior to this region by a factor >10, providing direct evidence of the predicted shadow of a black hole. There is a remarkable consistency among all methods and data sets. We compare the derived emission region and black hole parameters from these analyses with those recovered from reconstructed images. We further fit images generated from GRMHD models directly to the data. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the emission region and estimate physical properties of the source. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions. ![]() Across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. This stage allowed us to select parameters objectively to use when reconstructing images of M87. In the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. This stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). To assess the reliability of these results, we implemented a two-stage imaging procedure. The ring is persistent across four observing nights and shows enhanced brightness in the south. These images show a prominent ring with a diameter of ~40 μas, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions.Abstract:We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of similar to 40 mu as, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. ![]() Abstract We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength.
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