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Observing a black hole event horizon: (sub)millimeter VLBI of Sgr A*

Published online by Cambridge University Press:  06 January 2010

Vincent L. Fish  and
Sheperd S. Doeleman
Vincent L. Fish
Affiliation:
MIT Haystack Observatory, Off Route 40, Westford, MA 01886, USA email: [email protected], [email protected]
Sheperd S. Doeleman
Affiliation:
MIT Haystack Observatory, Off Route 40, Westford, MA 01886, USA email: [email protected], [email protected]
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Abstract

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Very strong evidence suggests that Sagittarius A*, a compact radio source at the center of the Milky Way, marks the position of a super massive black hole. The proximity of Sgr A* in combination with its mass makes its apparent event horizon the largest of any black hole candidate in the universe and presents us with a unique opportunity to observe strong-field GR effects. Recent millimeter very long baseline interferometric observations of Sgr A* have demonstrated the existence of structures on scales comparable to the Schwarzschild radius. These observations already provide strong evidence in support of the existence of an event horizon. (Sub)Millimeter VLBI observations in the near future will combine the angular resolution necessary to identify the overall morphology of quiescent emission, such as an accretion disk or outflow, with a fine enough time resolution to detect possible periodicity in the variable component of emission. In the next few years, it may be possible to identify the spin of the black hole in Sgr A*, either by detecting the periodic signature of hot spots at the innermost stable circular orbit or parameter estimation in models of the quiescent emission. Longer term, a (sub)millimeter VLBI “Event Horizon Telescope” will be able to produce images of the Galactic center emission to the see the silhouette predicted by general relativistic lensing. These techniques are also applicable to the black hole in M87, where black hole spin may be key to understanding the jet-launching region.

Keywords

black hole physicsaccretionaccretion disksGalaxy: centersubmillimetertechniques: interferometrictechniques: high angular resolution
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S261: Relativity in Fundamental Astronomy: Dynamics, Reference Frames, and Data Analysis , April 2009 , pp. 271 - 276
Copyright
Copyright © International Astronomical Union 2010

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