Anisotropy in the Angular Broadening of Sagittarius A * at the Galactic Center
Abstract
We present the results of a lambda = 20 cm (VLA) squared observation of the compact Galactic center radio source Sgr A(*). The scatter-broadened image is elongated in the east-west direction, with an axial ratio of 0.56 +/- 0.22 and a position angle of 82 deg +/- 1.8 deg. A similar shape and orientation has been found previously at shorter wavelengths using Very Long Base Interferometry (VLBI) and Very Long Baseline Array (VLBA). Both the major and minor axes follow the lambda squared law appropriate for scattering by turbulence in the intervening medium. We argue that the scattering occurs in thin ionized surface layers of molecular clouds lying in the central 100 pc of the Galaxy. The ionized regions are characterized by electron densities of 104/cu cm and milligauss magnetic field strengths, and are responsible for the diffuse free-free emission and the Faraday rotation in the region.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1994
- DOI:
- 10.1086/187575
- Bibcode:
- 1994ApJ...434L..63Y
- Keywords:
-
- Anisotropy;
- Galactic Nuclei;
- Molecular Clouds;
- Radio Sources (Astronomy);
- Sagittarius Constellation;
- Angular Distribution;
- Electron Density (Concentration);
- Light Scattering;
- Radio Astronomy;
- Very Large Array (Vla);
- Astrophysics;
- GALAXIES: ISM;
- GALAXY: CENTER;
- ISM: INDIVIDUAL NAME: SAGITTARIUS A *;
- ISM: INDIVIDUAL ALPHANUMERIC: IRS 16