7 millimeter VLBA observations of Sagittarius A*

被引:54
作者
Bower, GC
Backer, DC
机构
[1] Max Planck Inst Radioastron, D-53121 Bonn, Germany
[2] Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
[3] Univ Calif Berkeley, Radio Astron Lab, Berkeley, CA 94720 USA
基金
美国国家科学基金会;
关键词
galaxies; active; Galaxy; center; scattering;
D O I
10.1086/311259
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present 7 mm Very Long Baseline Array observations of the compact nonthermal radio source in the Galactic center; Sagittarius A*. These observations confirm the hypothesis that the image of Sgr A*:: is a resolved elliptical Gaussian caused by the scattering of an intervening thermal plasma. The measured major axis of Sgr A* is 0.76 +/- 0.04 mas, consistent with the predicted scattering size of 0.67 +/- 0.03. We find an axial ratio of 0.73 +/- 0.10 and a position angle of 77 degrees.0 +/- 7 degrees.4. These results are fully consistent with VLBI observations at longer wavelengths and at 3 mm. We find no evidence for any additional compact structure to a limit of 35 mJy. The underlying radio source must be smaller than 4.1 AU for a Galactocentric distance of 8.5 kpc. This result is consistent with the conclusion that the radio emission from Sgr A* results from synchrotron or cyclo-synchrotron radiation of gas in the vicinity of a black hole with a mass near 10(6) Mo-..
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页码:L97 / L100
页数:4
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