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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 |
| Institution: | 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 |