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Science 7 January 1983:
Vol. 219. no. 4580, pp. 54 - 56
DOI: 10.1126/science.219.4580.54
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Articles

Detection of a Compact Radio Source near the Center of a Gravitational Lens: Quasar Image or Galactic Core?

M. V. GORENSTEIN 1, I. I. SHAPIRO 1, N. L. COHEN 1, B. E. COREY 1, E. E. FALCO 1, J. M. MARCAIDE 1, A. E. E. ROGERS 2, A. R. WHITNEY 2, R. W. PORCAS 3, R. A. PRESTON 4, and A. RIUS 5

1 Department of Earth and Planetary Sciences and Department of Physics, Massachusetts Institute of Technology, Cambridge 02139
2 Haystack Observatory, Westford, Massachusetts 01886
3 Max Planck Institut für Radioastronomie, Bonn, Federal Republic of Germany
4 Jet Propulsion Laboratory, Pasadena, California 91125
5 NASA/Instituto Nacional de Tecnica Aeroespacial, Madrid, Spain

By use of a new, very sensitive interferometric system, a faint, compact radio source has been detected near the center of the galaxy that acts as the main part of a gravitational lens. This lens forms two previously discovered images of the quasar Q09S7+561, which lies in the direction of the constellation Ursa Major. The newly detected source has a core smaller than 0.002 arc second in diameter with a flux density of 0.6 ± 0.1 millijansky at the 13-centimeter wavelength of the radio observations. This source could be the predicted third image of the transparent gravitational lens, the central core of the galaxy, or some combination of the two. It is not yet possible to choose reliably between these alternatives.

Submitted on May 18, 1982


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Very-Long-Baseline Radio Interferometry: The Mark III System for Geodesy, Astrometry, and Aperture Synthesis.
A. E. E. Rogers, A. E. E. ROGERS, R. J. CAPPALLO, H. F. HINTEREGGER, J. I. LEVINE, E. F. NESMAN, J. C. WEBBER, A. R. WHITNEY, T. A. CLARK, C. MA, et al. (1983)
Science 219, 51-54
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