Physical Implications of the M87 Black Hole Shadow Image obtained by the Event Horizon Telescope

Cheng-Yu Kuo^1*, Keiichi Asada², Masanori Nakamura², Satoki Matsushita², Shoko Koyama², Kevin Koay², Paul Ho², Chih-Wei Huang², Jongho Park², Ming-Tang Chen²

¹Physics, National Sun Yat-Sen University, Kaosiung, Taiwan
²Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan

* Presenter:Cheng-Yu Kuo, email:cykuo@mail.nsysu.edu.tw

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. In this talk, we will first discuss the physical implications of the asymmetric ring seen in the 2017 EHT data based on a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations. We will show that the asymmetric ring is consistent with predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. After discussing the physical implications of the shadow image of M87, we will show the black hole mass inferred from the comparison between a set of geometric asymmetric ring models and the visibility data. In addition, we will demonstrate that the EHT observation of M87 is consistent with the presence of a central Kerr black hole, as predicted by the general theory of relativity. In the end of the talk, we will discuss briefly what physics we could learn from the first map of polarized emission from the vicinity of the M87 black hole which is expected to be published in the near future.

Keywords: gravity, gravitational lensing, black hole