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Multi-frequency VLBI Observations of the Gravitational Lens B0218+357

Published online by Cambridge University Press:  25 May 2016

R. W. Porcas  and
A. R. Patnaik
R. W. Porcas
Affiliation:
Max-Planck-Intitut fuer Radioastronomie, Bonn, Germany
A. R. Patnaik
Affiliation:
Max-Planck-Intitut fuer Radioastronomie, Bonn, Germany

Extract

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The gravitational lens system B0218+357 comprises 2 image components (A and B) and a radio ‘Einstein Ring’ (Patnaik et al, 1993). The redshift of the lens galaxy is 0.6847 (Browne et al, 1994) and that of the imaged source 0.96 (preliminary result; Lawrence et al, 1995). The separation of A and B, which are both flat-spectrum radio sources, is only 0.335 arcsec, leading to the hope that the lens is a single galaxy with a relatively simple mass distribution. Refsdal pointed out (1964) that a model of such a distribution, and a measurement of the time difference along the two image paths, leads to an estimate of the Hubble constant, independent of the usual steps in the distance ladder. B0218+357 is one of only a few lensed systems well suited for such measurements. A preliminary value of 12 days has been measured for the A-B time delay, derived from a comparison of the percentage polarisation variations of the images at 15GHz, using the VLA (Corbett et al, 1995).

Type
Properties of Radio Sources
Information
Symposium - International Astronomical Union , Volume 175: Extragalactic Radio Sources , 1996 , pp. 115 - 117
Copyright
Copyright © Kluwer 1996 

References

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