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Published November 20, 2000 | Published + Submitted
Journal Article Open

RX J0911+05: A Massive Cluster Lens at z =  0.769


We report the detection of a massive high-redshift cluster of galaxies near the quadruple quasar RX J0911+05, using the Low-Resolution Imaging Spectrograph instrument on the Keck II telescope. The cluster is found to have a mean redshift of z = 0.7689 ± 0.002 and a velocity dispersion of σ = 836^(+180)_(-200) km s^(-1), based on redshift measurements for 24 member galaxies. This massive high-redshift cluster is the origin of the unusually large external shear required by lensing models of the quadruple quasar system. We predict the expected time delay depending on the exact contribution of the cluster. A measurement of the time delay and further deep lensing and X-ray observations will unravel useful properties of this serendipitously discovered high-redshift cluster and may put interesting cosmological constraints on H_0.

Additional Information

© 2000 The American Astronomical Society. Received 2000 June 9; accepted 2000 August 23; published 2000 November 6. Part of the work presented is based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. The entire Keck/LRIS user community owes a huge debt to Jerry Nelson, Gerry Smith, Bev Oke, and many other people who have worked to make the Keck Telescope and LRIS a reality. We are grateful to the W. M. Keck Foundation and particularly its late president, Howard Keck, for the vision to fund the construction of the W. M. Keck Observatory. It is a pleasure to acknowledge the efficient and friendly support of the Keck Observatory staff. We also acknowledge useful discussions with C. Kochanek, F. Courbin, and I. Burud. This research was supported by CNRS/INSU for J.-P. K. and by the Danish Natural Science Research Council (SNF) for J. H.

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Published - Kneib_2000_ApJ_544_L35.pdf

Submitted - 0006106.pdf


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