Falcke, Melia, Agol: The Shadow of the Black Hole at the Galactic Center
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The Shadow of the Black Hole at the Galactic Center

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Heino Falcke^{1}, Fulvio Melia^{2}, Eric Agol^{3}

^{1} Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany (hfalcke@mpifr-bonn.mpg.de)

^{2}Steward Observatory and Department of Physics, University of
Arizona, Tucson, AZ 85721 (melia@physics.arizona.edu)

^{3}Physics and Astronomy Department, Johns Hopkins University,
Baltimore, MD 21218 (agol@pha.jhu.edu)
### in: Cosmic Explosions, 10th Astrophysics Conference, College Park, Maryland, eds. S.S. Holt and W.W. Zhang, AIP Conf. Ser., Vol. 522, p. 317

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**Abstract:**

We show that perhaps already with the next generation of
long-baseline interferometers at submm-wavelengths we will able to
image the shadow of the black hole in the Galactic Center. To a
distant observer, the event horizon casts a relatively large
``shadow'' with an apparent diameter of ~10 gravitational radii due
to bending of light by the black hole, nearly independent of the
black hole spin or orientation. The predicted angular size for the
Galactic Center black hole is 30 micro-arcseconds, a mere factor two
smaller than the highest currently achieved resolution with VLBI
techniques. Taking into account scatter-broadening of the image in
the interstellar medium and the finite achievable telescope
resolution, we show that the shadow of Sgr A* can be observed at
suitably high frequencies. The main problems are possible optical
depth effects for an ADAF model and Doppler boosting for a jet
model. This has an influence on which dynamic range and which
observing frequency is ultimately required to prove or disprove the
existence of an event horizon.

Paper: Available in full length as PostScript
and LaTex (AAS LaTex) Format.
Other publications can be found here.

Questions: Heino Falcke, hfalcke@mpifr-bonn.mpg.de