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Colloquia

First Sgr A* Event Horizon Telecope Results: The Shadow of the Supermassive Black Hole in the Center of the Milky Way

by Prof. Yosuke Mizuno (Tsung-Dao Lee Institute)

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Abstract
The 13th Tsung-Dao Lee Frontier Lecture  (18:30-19:30)
  
Title:  First Sgr A* Event Horizon Telecope Results: The Shadow of the Supermassive Black Hole in the Center of the Milky Way
 
Abstract:
We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength 1.3 mm. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of ~50 micro-arcsecond. Using a large suite of numerical simulations and model comparison, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 million solar mass, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way. In this talk, I will compare with two EHT observed black hole shadows, M87 and Sgr A*.
 
Panelists:  Zhiqiang Shen (SHAO), Xiaogang He (TDLI), Pengjie Zhang (TDLI), Yosuke Mizuno (TDLI), Yuzhu Cui (TDLI)
 
Colloquium (20:00-21:00)
 
Title: Testing Astrophysical Models from the Shadow of the Galactic Center Black Hole 


 

Abstract:
We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength 1.3 mm. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of ~50 micro-arcsecond. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 million solar mass, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies.  Our model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50 deg), as well as non-spinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way. In this talk, I will focus on more theoretical interpretation and model comparison to understand the accretion flow properties nearby Sgr A*.
Biography

Yosuke Mizuno is T.D. Lee Fellow and Associate Professor at Tsung-Dao Lee Institute in Shanghai Jiao Tong University. He obtained a PhD from Kyoto University in 2004. He was a postdoc at Department of Astronomy, Kyoto University, Japan (2004-2005), NASA postdoctoral program fellow at NASA Marshall space flight center, USA (2005-2008), research scientist at University of Alabama in Huntsville, USA (2008-2011), associate research scholar at National Tsing-Hua University, Taiwan, China (2011-2014), and research associate at Goethe University Frankfurt, Germany (2014-2020). He joined Tsung-Dao Lee Institute on October 2020. He is a Theory & Simulation Working Group coordinator (2017-present) on Event Horizon Telescope collaboration. He has worked on relativistic astrophysics, plasma astrophysics, and high-energy astrophysics by using numerical simulations. He has received a number of awards, including 2019 Breakthrough Prize in Fundamental Physics and Einstein Medal 2020 under EHT collaboration. 


 

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