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An origin of the radio jet in M87 at the location of the central black hole

An Erratum to this article was published on 08 August 2012


Powerful radio jets from active galactic nuclei are thought to be powered by the accretion of material onto the supermassive black hole (the ‘central engine’)1,2. M87 is one of the closest examples of this phenomenon, and the structure of its jet has been probed on a scale of about 100 Schwarzschild radii (Rs, the radius of the event horizon)3. However, the location of the central black hole relative to the jet base (a bright compact radio ‘core’) remains elusive4,5. Observations of other jets indicate that the central engines are located about 104–106Rs upstream from the radio core6,7,8,9. Here we report radio observations of M87 at six frequencies that allow us to achieve a positional accuracy of about 20 microarcseconds. As the jet base becomes more transparent at higher frequencies, the multifrequency position measurements of the radio core enable us to determine the upstream end of the jet. The data reveal that the central engine of M87 is located within 14–23Rs of the radio core at 43 GHz. This implies that the site of material infall onto the black hole and the eventual origin of the jet reside in the bright compact region seen on the image at 43 GHz.

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Figure 1: Schematic diagram explaining the radio core shift of a jet.
Figure 2: Plot of the core-shift measurements in right ascension for M87 as a function of observing frequency.
Figure 3: VLBA image of M87 at 43 GHz superimposed on the measured core-shift positions.


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We thank M. Honma, H. Sudou and T. Hirota for discussions about the astrometry analysis; and K. Asada, G. Giovannini, M. Giroletti, M. Inoue, S. Kameno, S. Koide, S. Sasaki, Ł. Stawarz, N. Sugiyama and N. Yoshida for comments. The Very Long Baseline Array is operated by the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. This work was supported in part by the Graduate University for Advanced Studies (Sokendai).

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Authors and Affiliations



K.H., A.D. and H.N. designed and proposed the VLBA observations. K.H. led the work and together with A.D. performed the data analysis. K.H., M.K. and Y.H. jointly wrote the paper. N.K. checked the manuscript. All the authors discussed the results and commented on the manuscript.

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Correspondence to Kazuhiro Hada.

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The authors declare no competing financial interests.

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This file contains Supplementary Methods, Supplementary References, Supplementary Figures 1-5 with legends and Supplementary Tables 1-2. (PDF 3741 kb)

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Hada, K., Doi, A., Kino, M. et al. An origin of the radio jet in M87 at the location of the central black hole. Nature 477, 185–187 (2011).

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