A ring-like accretion structure in M87 connecting its black hole and jet

The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. 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 hole3. Here we report 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 shows a ring-like structure of [Formula: see text] Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition\ua0to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. 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 Ring-Like Accretion Structure in M87 Connecting Its Black Hole and Jet

The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. 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 hole3. Here we report 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 shows a ring-like structure of 8.4+0.5−1.1 Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. 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 ring-like accretion structure in M87 connecting its black hole and jet

The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation^{1,2}. 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^3. Here we report 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 shows a ring-like structure of 8.4_{-1.1}^{+0.5} Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. 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.Comment: 50 pages, 18 figures, 3 tables, author's version of the paper published in Natur

Towards the design, synthesis, and structural characteristics of peptidomimetic scaffolds: beta-amino acids to bisisoxazolidines.

Organic molecules that mimic key protein structural motifs have been shown to mediate protein-protein interactions involved in a number of biological processes. An area where such chemical tools are particularly useful is gene regulation at the transcriptional level, a process mediated via many poorly understood protein-protein interactions. The correlation between a number of human disease states and the aberrant regulation of these events has led to a concentrated effort in developing peptidomimetics to elucidate these complex mechanisms and to serve as ligands for the artificial control of this process. Chapter I details the historical challenges and some advances in the development of such molecules. beta-Peptides, oligomers of beta-amino acids, have enormous potential in this context due to their capacity to adopt discrete, stable conformations in biological systems. However, the use of beta-peptides in this application is ultimately limited by the lack of efficient synthetic methods for the preparation of the highly substituted and stereoisomerically pure constituents. Chapter II details the development of a conceptually unique synthetic approach that uses chiral isoxazolidines as key intermediates to access densely functionalized beta-amino acids difficult to realize by conventional means. Chapter III details the expansion of this synthetic method to provide isoxazolidines that contain functional groups analogous to those found in natural transcriptional activators that serve as effective small molecule components in gene upregulation, presumably by mediating protein-protein interactions involved in this process. Chapter IV details the development of an iterative synthetic approach to synthesize extended versions of the active isoxazolidines that have enhanced biological activity, seemingly due to increased surface area and functionality available for protein surface recognition. An account of the structural details of this class of compounds is also discussed. By utilizing a synthetic strategy that provides control over both the stereochemistry and functionality present in the molecule, this novel foldamer motif is also an attractive target for future applications ranging from catalysis to hydrogen storage.Ph.D.BiochemistryOrganic chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125166/2/3186709.pd