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Radio, optical and infrared observations of CLASS B0128+437 | | A. D. Biggs
; I. W. A. Browne
; N. J. Jackson
; T. York
; M. A. Norbury
; J. P. McKean
; P. M. Phillips
; | | Date: |
5 Feb 2004 | | Journal: | Mon.Not.Roy.Astron.Soc. 350 (2004) 949 | | Subject: | astro-ph | | Affiliation: | 1 and 2), I. W. A. Browne , N. J. Jackson , T. York , M. A. Norbury , J. P. McKean , P. M. Phillips ( JIVE, JBO | | Abstract: | We present new observations of the gravitational lens system CLASS B0128+437. HST observations detect a very faint, extended object in I-band with no emission from the lensed images visible; no detection at all is made in V-band. The lens system is detected with much higher signal to noise with UKIRT in K-band, but the resolution is not sufficient to allow the lensed images and the lens galaxy to be separated. A careful astrometric calibration, however, suggests that the peak of the infrared emission corresponds to the two merging images A and B and therefore that the lensed images dominate at infrared wavelengths. The new radio data consist of VLBI radio images at three frequencies, 2.3, 5 and 8.4GHz, made with the VLBA and the 100-m Effelsberg telescope. The lensed source consists of three well-defined sub-components embedded in a more extended jet. Due to the fact that the sub-components have different spectral indices it is possible to determine which part of each image corresponds to the same source sub-component. Our main finding is that one of the images, B, looks very different to the others, there being no obvious division into separate sub-components and the image being apparently both broader and smoother. This is a consequence we believe of scatter-broadening in the ISM of the lensing galaxy. The large number of multiply-imaged source sub-components also provide an abundance of modelling constraints and we have attempted to fit an SIE+external shear model to the data, as well as utilising the novel method of Evans & Witt. It proves difficult in both cases, however, to obtain a satisfactory fit which strongly suggests the presence of sub-structure in the mass distribution of the lensing galaxy, perhaps of the kind that is predicted by CDM theories of structure formation. | | Source: | arXiv, astro-ph/0402128 | | Services: | Forum | Review | PDF | Favorites | |
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