Discovery of a Strongly Lensed Galaxy atz=3.9 behind az=0.83 Galaxy Cluster

We report the discovery and spectroscopic confirmation of threegravitationally-lensed images of a galaxy at z=3.9 in the background of adistant, rich cluster of galaxies at z=0.83, on the basis of observations withFaint Object Camera And Spectrograph (FOCAS) on the Subaru telescope. Weconstruct a simple lens model of the cluster mass distribution based on Jee etal.'s weak lensing mass estimates from deep, high-resolution images by AdvancedCamera for Surveys (ACS) on the Hubble Space Telescope. The lens model canaccount simultaneously for the observed image configuration and the flux ratioof the closer pair located close to the critical curve. The parities of thethree images are also consistent with the lensing hypothesis. Since this galaxyis apparently bright (i'_{AB} \sim 23.7) for its redshift due to themagnification, it serves as a good high redshift target on which we can makeextensive and detailed studies based on multi-wavelength imaging andspectroscopy.Comment: 4 pages, 3 figures, 1 table, accepted for publication in PAS