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Global 8.4-GHz VLBI observations of JVAS B0218+357

A. D. Biggs·O. Wucknitz·R. W. Porcas·I. W. A. Browne·N. J. Jackson·S. Mao·P. N. Wilkinson
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Abstract

In this paper we present new observations of the gravitational lens system JVAS B0218+357 made with a global VLBI network at a frequency of 8.4 GHz. Our maps have an rms noise of 30 microJy/beam and with these we have been able to image much of the extended structure of the radio jet in both the A and B images at high resolution (~1 mas). The main use of these maps will be to enable us to further constrain the lens model for the purposes of H0 determination. We are able to identify several sub-components common to both images with the expected parity reversal, including one which we identify as a counter-jet. We have not been successful in detecting either the core of the lensing galaxy or a third image. Using a model of the lensing galaxy we have back-projected both of the images to the source plane and find that they agree well. However, there are small, but significant, differences which we suggest may arise from multi-path scattering in the ISM of the lensing galaxy. We also find an exponent of the radial mass distribution of approximately 1.04, in agreement with lens modelling of published 15-GHz VLBI data. Polarisation maps of each image are presented which show that the distributions of polarisation across images A and B are different. We suggest that this results from Faraday rotation and associated depolarisation in the lensing galaxy.

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A. D. Biggs, O. Wucknitz, R. W. Porcas, I. W. A. Browne, N. J. Jackson, S. Mao, P. N. Wilkinson. 2002-09-10. Global 8.4-GHz VLBI observations of JVAS B0218+357. https://doi.org/10.1046/j.1365-8711.2003.06050.x

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