An Efficient Search for Gravitationally Lensed Radio Lobes

We performed an automated comparison of the FIRST radio survey with the Automatic Plate Measuring (APM) optical catalog to find radio lobes with optical counterparts. Based on an initial survey covering ~3000 deg2, we selected a sample of 33 lens candidates for VLA confirmation. VLA and optical observations of these candidates yielded two lens systems, one a new discovery (J0816+5003) and one that was previously known (J1549+3047). Two other candidates have radio lobes with galaxies superposed but lack evidence of multiple imaging. One of our targets (J0958+2947) is a projected close pair of quasars (8'' separation at redshifts 2.064 and 2.744). Our search method is highly efficient, with greater than 5% of our observing targets being lensed, compared to the usual success rate of less than 1%. Using the whole FIRST survey, we expect to find five to 10 lenses in short order using this approach, and the sample could increase to hundreds of lensed lobes in the northern sky, using deeper optical surveys and planned upgrades to the VLA. Such a sample would be a powerful probe of galaxy structure and evolution.

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