Imaging the Black Hole Shadow with the Event Horizon Telescope

Shoko Koyama^1*, Greenland Telescope and VLBI group¹, Event Horizon Telescope Collaboration¹

¹Astronomy, Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan

* Presenter:Shoko Koyama, email:skoyama@asiaa.sinica.edu.tw

The Event Horizon Telescope (EHT), an earth-size millimeter Very Long Baseline Interferometry (VLBI) network of radio telescopes has successfully produced the first image of a black hole shadow, at the center of the representative nearby low luminosity Active Galactic Nuclei (AGN) M87. We present an overview of the observations, data processing, and imaging. The images show the asymmetric emission ring with a diameter of ~40 micro-arcseconds, with enhanced brightness in the south. The asymmetry in brightness in the ring can be explained by relativistic beaming of the synchrotron emission from a plasma rotating around the supermassive black hole. Although the diameter of the shadow confines the 6.5 billion solar masses, the extended jet emission was not imaged with the capability of the 2017 EHT observations. Probing the innermost jets at the vicinity of the black hole shadow is crucial for understanding jet launching mechanisms, and is expected to be revealed with the next EHT observations (2020-) with the enhanced capabilities.

Keywords: Radio Astronomy, Black Hole, Active Galactic Nuclei, Very Long Baseline Interferometry