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Structure of Sagittarius A* at 86 GHz using VLBI Closure Quantities

Doeleman, S. S. and Shen, Z.-Q. and Rogers, A. E. E. and Bower, G. C. and Wright, M. C. H. and Zhao, J. H. and Backer, D. C. and Crowley, J. W. and Freund, R. W. and Ho, P. T. P. and Lo, K. Y. and Woody, D. P. (2001) Structure of Sagittarius A* at 86 GHz using VLBI Closure Quantities. Astronomical Journal, 121 (5). pp. 2610-2617. ISSN 0004-6256. https://resolver.caltech.edu/CaltechAUTHORS:20190723-075508773

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Abstract

At radio wavelengths, images of the compact radio source Sagittarius A* (Sgr A*) in the Galactic center are scatter broadened with a λ^2 dependence due to an intervening ionized medium. We present VLBI observations of Sgr A* at 86 GHz using a six station array, including the VLBA antennas at Pie Town, Fort Davis, and Los Alamos, the 12 m antenna at Kitt Peak, and the millimeter arrays at Hat Creek and Owens Valley. To avoid systematic errors due to imperfect antenna calibration, the data were modeled using interferometric closure information. The data are best modeled by a circular Gaussian brightness distribution of FWHM 0.18 ± 0.02 mas. The data are also shown to be consistent with an elliptical model corresponding to the scattering of a point source. The source structure in the north-south direction, which is less well determined than in the east-west direction because of the limited north-south u-v coverage of the array, is constrained to be less than 0.27 mas by these measurements. These results are consistent with extrapolations of intrinsic structure estimates obtained with VLBI at a 7 mm wavelength, assuming the intrinsic size of Sgr A* has a greater dependence than λ^(0.9) with wavelength.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1086/320376DOIArticle
Additional Information:© 2001 The American Astronomical Society. Received 2000 September 21; accepted 2001 January 24. We thank the staff at the participating observatories for help with the observations and the staff of Haystack Observatory for correlating the data. We also thank Ramesh Narayan and Feryal Özel for making data on their ADAF models available to us prior to publication.
Subject Keywords:Galaxy: center - galaxies : individual (Sagittarius) - techniques: interferometric
Issue or Number:5
Record Number:CaltechAUTHORS:20190723-075508773
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190723-075508773
Official Citation:S. S. Doeleman et al 2001 AJ 121 2610
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97344
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:23 Jul 2019 16:38
Last Modified:03 Oct 2019 21:30

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