Detection of the Intrinsic Size of Sagittarius A* through Closure Amplitude Imaging

Geoffrey C. Bower(1), Heino Falcke(2), Robeson M. Herrnstein(3), Jun-Hui Zhao(4), W.M. Goss(5), Donald C. Backer(1)

(1) Astronomy Department & Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA
(2) Radio Observatory Westerbork, ASTRON, P.O. Box 2 , 7990 AA Dwingeloo, The Netherlands
(3) Department of Astronomy, Columbia University, Mail Code 5246, 550 West 120th St., New York,NY 10027, USA
(4) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138, USA
(5) National Radio Astronomy Observatory, Array Operations Center, P.O. Box O, Socorro, NM 87801, USA

Paper: Science, in press

EPrint Server: astro-ph/0404001


We have detected the intrinsic size of Sagittarius A*, the Galactic Center radio source associated with a supermassive black hole, showing that the short-wavelength radio emission arises from very near the event horizon of the black hole. Radio observations with the Very Long Baseline Array show that the source has a size of 24 +/- 2 Schwarzschild radii at 7 mm wavelength. In one of eight 7-mm epochs we also detect an increase in the intrinsic size of 60+25_-17%. These observations place a lower limit to the mass density of Sgr A* of 1.4*104 solar masses per cubic astronomical unit.

Preprints available from the authors at , or the raw TeX (no figures) if you click here.

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