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Published July 1, 1995 | Published
Journal Article Open

1608+656: A Quadruple-Lens System Found in the CLASS Gravitational Lens Survey


The first phase of a large gravitational lens survey using the Very Large Array at a wavelength of 3.6 cm has been completed, yielding images for 3258 radio sources. The Cosmic Lens All-Sky Survey (CLASS) is designed to locate gravitational lens systems consisting of multiply imaged compact components with separations greater than 0."2. We report here the first discovery of a gravitational lens from the survey: 1608+656, a quadruply imaged object with a maximum separation of 2."1. Images from the Palomar 5 m and Keck 10 m telescopes show the lensed images and the lensing galaxy. An optical spectrum obtained with the Palomar 5 m telescope indicates a redshift of z=0.6304 for the lensing galaxy. No conclusive redshift for the lensed object has been determined, although a single strong emission line is found at 9240 Å in the Keck low-resolution imaging spectrograph spectrum. The two most likely identifications for this line are Hβ (z=0.90) and Mg II (z=2.30). The preliminary lens model derived from the radio image reproduces the observed configuration and relative fluxes of the images, as well as the position, shape, and orientation of the lensing galaxy. Because a simple mass model is able to fit the observations, we argue that this lens system is promising for determining H_0.

Additional Information

© 1995 American Astronomical Society. Received 1995 March 6; accepted 1995 April 18. S. T. M. is supported by an R. A Millikan Fellowship at Caltech. CLASS at Caltech is supported by NSF grant AST-9117100. S. G. D. was supported by NSF PYI award AST-9157412. Infrared astrophysics at Caltech is supported by a grant from the NSF. D. S. W. acknowledges support of a Hubble Fellowship provided by NASA through grant HF-1040.01-92A from the STScl, which is operated by the AURA. We thank the staff of the VLA and the Palomar and Keck observatories for their assistance during our observing runs. S. T. M. also acknowledges the hospitality of the ITP in Santa Barbara, which is supported by the NSF under grant PHY89-04035, during the completion of this manuscript.

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Published - 1995ApJ___447L___5M.pdf


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