Anisotropy in the angular broadening of Sagittarius A* at the Galactic center

Farhad Yusef-Zadeh, William Cotton, Mark Wardle, Fulvio Melia, Douglas A. Roberts

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Abstract

We present the results of a λ = 20 cm VLA2 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° ± 1°.8. A similar shape and orientation has been found previously at shorter wave-lengths using VLBI and VLBA. Both the major and minor axes follow the λ2 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 cm-3 and milligauss magnetic field strengths, and are responsible for the diffuse free-free emission and the Faraday rotation in the region.

Original languageEnglish (US)
Pages (from-to)L63-L66
JournalAstrophysical Journal
Volume434
Issue number2 PART 2
StatePublished - Oct 20 1994

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Keywords

  • Galaxies: ISM
  • Galaxy: center
  • ISM: individual (Sagittarius A*, IRS 16)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Yusef-Zadeh, F., Cotton, W., Wardle, M., Melia, F., & Roberts, D. A. (1994). Anisotropy in the angular broadening of Sagittarius A* at the Galactic center. Astrophysical Journal, 434(2 PART 2), L63-L66.