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Doeleman, Sheperd

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Doeleman

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Sheperd

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Doeleman, Sheperd

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2011 - 20122

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Author's Publications: search.filters.isAuthorOfPublication.a5f60922-1189-46a1-8cdf-001484994cf6

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    Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87
    (American Association for the Advancement of Science (AAAS), 2012) Doeleman, Sheperd; Fish, V. L.; Schenck, D. E.; Beaudoin, C.; Blundell, Raymond; Bower, G. C.; Broderick, Alithia Carol; Chamberlin, R.; Freund, R.; Friberg, P.; Gurwell, Mark; Ho, Po-Yi; Honma, M.; Inoue, M.; Krichbaum, T. P.; Lamb, Justin; Loeb, Abraham; Lonsdale, C.; Marrone, D. P.; Moran, James; Oyama, T.; Plambeck, R.; Primiani, Rurik; Rogers, A. E. E.; Smythe, D. L.; SooHoo, J.; Strittmatter, P.; Tilanus, R. P. J.; Titus, M.; Weintroub, Jonathan; Wright, Bennett Bennett; Young, K. H.; Ziurys, L. M.
    Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by accretion of matter onto super massive black holes. While the measured width profiles of such jets on large scales agree with theories of magnetic collimation, predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations at 1.3mm wavelength of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 +/- 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.
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    1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales
    (IOP Publishing, 2011) Fish, Vincent L.; Doeleman, Sheperd; Beaudoin, Christopher; Blundell, Raymond; Bolin, David E.; Bower, Geoffrey C.; Chamberlin, Richard; Freund, Robert; Friberg, Per; Gurwell, Mark; Honma, Mareki; Inoue, Makoto; Krichbaum, Thomas P.; Lamb, James; Marrone, Daniel P.; Moran, James; Oyama, Tomoaki; Plambeck, Richard; Primiani, Rurik; Rogers, Alan E. E.; Smythe, Daniel L.; SooHoo, Jason; Strittmatter, Peter; Tilanus, Remo P. J.; Titus, Michael; Weintroub, Jonathan; Wright, Melvyn; Woody, David; Young, Ken; Ziurys, Lucy M.
    Sagittarius A*, the ~4 × 106 M ☉ black hole candidate at the Galactic center, can be studied on Schwarzschild radius scales with (sub)millimeter wavelength very long baseline interferometry (VLBI). We report on 1.3 mm wavelength observations of Sgr A* using a VLBI array consisting of the JCMT on Mauna Kea, the Arizona Radio Observatory's Submillimeter Telescope on Mt. Graham in Arizona, and two telescopes of the CARMA array at Cedar Flat in California. Both Sgr A* and the quasar calibrator 1924–292 were observed over three consecutive nights, and both sources were clearly detected on all baselines. For the first time, we are able to extract 1.3 mm VLBI interferometer phase information on Sgr A* through measurement of closure phase on the triangle of baselines. On the third night of observing, the correlated flux density of Sgr A* on all VLBI baselines increased relative to the first two nights, providing strong evidence for time-variable change on scales of a few Schwarzschild radii. These results suggest that future VLBI observations with greater sensitivity and additional baselines will play a valuable role in determining the structure of emission near the event horizon of Sgr A*.