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Title: Observing the Supermassive Black Hole at the Center of M87 using EHT and GMVA+ALMA

Speaker: 박종호 교수 (경희대학교)

Date&Time: 2023-11-03, 11:00 AM

Location: 과학관 B102호 (Science Hall, B102)

Language: English

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Abstract:

The nearby radio galaxy M87 is a prime target to study black hole accretion and jet formation. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure which was interpreted as gravitationally lensed emission around a central black hole. Here we report new images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High resolution imaging reveals a ringlike structure of 8.4-1.1+0.5 Schwarzschild radii in diameter, ~50% larger than that seen at 1.3 mm, with the outer edge at 3.5 mm also being larger than that at 1.3 mm. This larger and thicker ring indicates a significant contribution from the accretion flow with high self-absorption opacity effects, added to the gravitationally lensed ring-like emission. Close to the black hole, the emission profile of the jet launching region is wider than the expected profile of a black hole driven jet, suggesting the possible presence of a wind associated with the accretion flow. A paper summarizing these findings has been published in the journal Nature. During this presentation, I will discuss the physical significance of the M87 black hole images captured at 1.3 and 3.5 mm, as well as the experiments underway in Korea that aim to provide further insight into the characteristics of this black hole.