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A new quadruple gravitational lens system: CLASS B0128+437 |
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| Authors: | P. M. Phillips M. A. Norbury L. V. E. Koopmans I. W. A. Browne N. J. Jackson P. N. Wilkinson A. D. Biggs R. D. Blandford A. G. de Bruyn C. D. Fassnacht P. Helbig S. Mao D. R. Marlow S. T. Myers T. J. Pearson A. C. S. Readhead D. Rusin E. Xanthopoulos |
| Affiliation: | University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL;Kapteyn Astronomical Institute, Postbus 800, NL-9700 AV Groningen, the Netherlands;California Institute of Technology, Pasadena, CA 91125, USA;Netherlands Foundation for Research in Astronomy, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands;National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA;Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104, USA |
| Abstract: | High-resolution MERLIN observations of a newly discovered four-image gravitational lens system, B0128+437, are presented. The system was found after a careful re-analysis of the entire CLASS data set. The MERLIN observations resolve four components in a characteristic quadruple-image configuration; the maximum image separation is 542 mas and the total flux density is 48 mJy at 5 GHz. A best-fitting lens model with a singular isothermal ellipsoid results in large errors in the image positions. A significantly improved fit is obtained after the addition of a shear component, suggesting that the lensing system is more complex and may consist of multiple deflectors. The integrated radio spectrum of the background source indicates that it is a gigahertz peaked spectrum source. It may therefore be possible to resolve structure within the radio images with deep VLBI observations and thus to constrain the lensing mass distribution better. |
| Keywords: | quasars: individual: B0128+437 cosmology: observations gravitational lensing |