COSMOLOGY: GRAVITATIONAL LENSING; COSMOLOGY: DARK MATTER; GALAXIES: QUASARS: INDIVIDUAL: B0827+525
Abstract :
[en] We present radio, optical, near-infrared and spectroscopic observations of the source B0827+525. We consider this source as the best candidate from the Cosmic Lens All-Sky Survey (CLASS) for a `dark-lens' system or binary radio-loud quasar. The system consists of two radio components with somewhat different spectral indices, separated by 2.815 arcsec. VLBA observations show that each component has substructure on a scale of a few mas. A deep K-band exposure with the W.M. Keck-II Telescope reveals emission near both radio components. The K-band emission of the weaker radio component appears extended, whereas the emission from the brighter radio component is consistent with a point source. Hubble Space Telescope F160W-band observations with the NICMOS instrument confirms this. A redshift of 2.064 is found for the brighter component, using the LRIS instrument on the W.M. Keck-II Telescope. The probability that B0827+525 consists of two unrelated compact flat-spectrum radio sources is ~ 3%, although the presence of similar substructure in both component might reduce this. We discuss two alternative scenarios to explain this system: (i) CLASS B0827+525 is a `dark-lens' system or (ii) B0827+525 is a binary radio-loud quasar. B0827+525 has met all criteria that thus far have in 100% of the cases confirmed a source as an indisputable gravitational lens system. Despite this, no lens galaxy has been detected with m_F160W<=23 mag. Hence, we might have found the first binary radio-loud quasar. At this moment, however, we feel that the `dark-lens' hypothesis cannot yet be fully excluded.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Koopmans, L. V. E.; California Institute of Technology, Pasadena, CA 91125, USA ; University of Manchester, NRAL Jodrell Bank, Macclesfield, Cheshire SK11 9DL, England, UK
de Bruyn, A. G.; NFRA, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands ; Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands
Fassnacht, C. D.; California Institute of Technology, Pasadena, CA 91125, USA ; NRAO, P.O.Box O, Socorro, NM 87801, USA
Marlow, D. R.; University of Manchester, NRAL Jodrell Bank, Macclesfield, Cheshire SK11 9DL, England, UK ; University of Pennsylvania, Department of Physics, Philadelphia, PA 19104, USA
Rusin, D.; University of Pennsylvania, Department of Physics, Philadelphia, PA 19104, USA
Blandford, R. D.; California Institute of Technology, Pasadena, CA 91125, USA
Browne, I. W. A.; University of Manchester, NRAL Jodrell Bank, Macclesfield, Cheshire SK11 9DL, England, UK
Helbig, Phillip ; Affiliation : Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands
Jackson, N.; University of Manchester, NRAL Jodrell Bank, Macclesfield, Cheshire SK11 9DL, England, UK
Myers, S. T.; University of Pennsylvania, Department of Physics, Philadelphia, PA 19104, USA ; NRAO, P.O.Box O, Socorro, NM 87801, USA
Pearson, T. J.; California Institute of Technology, Pasadena, CA 91125, USA
Readhead, A. C. S.; California Institute of Technology, Pasadena, CA 91125, USA
Wilkinson, P. N.; University of Manchester, NRAL Jodrell Bank, Macclesfield, Cheshire SK11 9DL, England, UK
Xanthopoulos, E.; University of Manchester, NRAL Jodrell Bank, Macclesfield, Cheshire SK11 9DL, England, UK
Hoekstra, H.; Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands)
