A lensed arc in the low-redshift cluster Abell 2124

We report the discovery of an arclike object 27 " from the center of the cD galaxy in the redshift z = 0.066 cluster A2124. Observations with the Keck II telescope reveal that the object is a background galaxy at z = 0.573, apparently lensed into an are of length similar to 8." 5 and total R magnitude m(R) = 20.86 +/- 0.07. The width of the are is resolved; we estimate it to be similar to 0." 6 after correcting for seeing. A lens model of the A2124 core mass distribution consistent with the cluster galaxy velocity dispersion reproduces the observed are geometry and indicates a magnification factor greater than or similar to 9. With this magnification, the strength of the [O II] lambda 3727 line implies a star formation rate of similar to 0.4 h(-2) M-circle dot yr(-1). A2124 thus appears to be the lowest redshift cluster known to exhibit strong lensing of a distant background galaxy.