Detection of the intrinsic size of Sagittarius A* through closure amplitude imaging.
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-millimeter wavelength. In one of eight 7-millimeter epochs, we also detected an increase in the intrinsic size of 60(-17)(+25)%. These observations place a lower limit to the mass density of Sagittarius A* of 1.4 x 10(4) solar masses per cubic astronomical unit.
Bower
Geoffrey C
GC
Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA. gbower@astro.berkeley.edu
Falcke
Heino
H
Herrnstein
Robeson M
RM
Zhao
Jun-Hui
JH
Goss
W M
WM
Backer
Donald C
DC