VLBI phase-reference observations of the gravitational lens JVAS B0218+357

Abstract

We present the results of phase-referenced VLBA+Effelsberg observations at five frequencies of the double-image gravitational lens JVAS B0218+357, made to establish the precise registration of the A and B lensed image positions. The motivation behind these observations is to investigate the anomalous variation of the image flux density ratio (A/B) with frequency - this ratio changes by almost a factor of two over a frequency range from 1.65 GHz to 15.35 GHz. We investigate whether frequency dependent image positions, combined with a magnification gradient across the image field, could give rise to the anomaly. Our observations confirm the variation of image flux ratio with frequency. The results from our phase-reference astrometry, taken together with the lens mass model of Wucknitz et al. (2004), show that shifts of the image peaks and centroids are too small to account for the observed frequency-dependent ratio.

arXiv comment10 pages, 8 figures, accepted by A&A

References in corpus (6)

• Time delay for the gravitational lens system B0218+357
• The Hubble constant from gravitational lens CLASS B0218+357 using the Advanced Camera for Surveys
• Models for the lens and source of B0218+357 - A LensClean approach to determine H0
• The Redshift of the Lensed Object in the Einstein Ring B0218+357
• Further Investigation of the Time Delay, Magnification Ratios, and Variability in the Gravitational Lens 0218+357
• Global 8.4-GHz VLBI observations of JVAS B0218+357

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• COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VIII. Deconvolution of high resolution near-IR images and simple mass models for 7 gravitationally lensed quasars
• Free-free absorption in the gravitational lens JVAS B0218+357
• A revised lens time delay for JVAS B0218+357 from a reanalysis of VLA monitoring data
• A new VLA/e-MERLIN limit on central images in the gravitational lens system CLASS B1030+074
• Isotopic ratios at z=0.68 from molecular absorption lines toward B 0218+357
• Formaldehyde Anti-Inversion at z=0.68 in the Gravitational Lens B0218+357
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• Radio follow-up of the gamma-ray flaring gravitational lens JVAS B0218+357
• Distribution of the molecular absorption in front of the quasar B0218+357
• Variability of GeV gamma-ray emission in QSO B0218+357 due to microlensing on intermediate size structures
• Multiwavelength study of the gravitationally lensed blazar QSO B0218+357 between 2016 and 2020
• Modeling the Images of Relativistic Jets Lensed by Galaxies with Different Mass Surface Density Distributions
• High-resolution imaging with the International LOFAR Telescope: Observations of the gravitational lenses MG 0751+2716 and CLASS B1600+434