VLBI phase-reference observations of the gravitational lens JVAS B0218+357
DOI: 10.1051/0004-6361:20054012 (http) or 10.1051/0004-6361:20054012 (doi)
ADS bibcode 2006A&A...447..515M
astro-ph/0508198
Rupal Mittal [1], Richard Porcas [1], Olaf Wucknitz [2,3], Andy Biggs [3,4], Ian Browne [5]
- MPIfR, Bonn
- Universität Potsdam
- JIVE, Dwingeloo
- UK ATC, Edinburgh
- JBO, Manchester
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.
A&A 447 (2006) 515 (link to online journal)
DOI (Digital Object Identifier): 10.1051/0004-6361:20054012 (http) or 10.1051/0004-6361:20054012 (doi)
ADS bibcode 2006A&A...447..515M (link to ADS entry)
astro-ph/0508198 (link to e-print archive)
download full article (A&A version)
PDF file (399.9 kB, last change 24 Feb 2006)
10 pages
To publications
To my homepage
To the AIfA
To the University of Bonn
Script last modified on 7 Sep 2010
Last change to this data base entry on 24 Feb 2006