CLASS B1152+199 and B1359+154: Two New Gravitational Lens Systems Discovered in the Cosmic Lens All-Sky Survey

Abstract

The third phase of the Cosmic Lens All-Sky Survey (CLASS) has recently been completed, bringing the total number of sources imaged to over 15,000 in the CLASS and Jodrell-VLA Astrometric Survey combined survey. In the VLA observations carried out in 1998 March and April, two new candidate lensed systems were discovered: CLASS B1152+199 and B1359+154. B1152+199 is a 1."6 double, with a background quasar at z = 1.019 lensed by a foreground galaxy at z = 0.439. The relatively flat radio spectra of the lensed images (α^(14.94)_(-8.46) = -0.32), combined with a previous ROSATdetection of the source, make B1152+199 a strong candidate for time delay studies at both radio and X-ray wavelengths. B1359+154 is a quadruply lensed quasar at z = 3.235, with a maximum image separation of 1."7. As yet, the redshift of the lensing object in this system is undetermined. The steep spectral index of the source (α^(14.94)_(-8.46) = -0.9) suggests that B1359+154 will not exhibit strong variability and is therefore unlikely to be useful for determining H_0 from measured time delays.

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