Oral Presentation

Imaging the Black Hole Shadow with the Event Horizon Telescope

Author(s): Shoko Koyama (ASIAA), EHT Collaboration

Presenter: Shoko Koyama (ASIAA)

The first image of a black hole shadow in M87 was successfully produced with the Event Horizon Telescope (EHT) and phased ALMA at 1.3 mm. We will introduce the imaging process which does not rely on any theoretical models. To asses the reliability of the results, first, four teams independently produced the images using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). Secondly, we reconstructed synthetic data from a large survey of imaging parameters and compared the results with the truth images in order to select best parameters for M87 imaging. The resulting M87 images show the asymmetric emission ring with a diameter of ~40 micro-arcseconds, with enhanced brightness in the south. Across all tests, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique.