Hubble Space Telescope Imaging of the Large-Redshift Gravitational Lens Candidate 1208+1011

Abstract

Four-color photometry obtained with the Hubble Space Telescope is consistent with the hypothesis that the light from the quasar 1208+1011 (z = 3.8) is gravitationally lensed. Guided exposures taken with the HST Planetary Camera resolve the quasar image into two point-source components separated by 0.476" +/- 0.004". The intensity ratio of the components is approximately 4:1 in each of four broad-band HST filters with mean wavelengths of 4352, 5416, 6898, and 8922 A. The HST photometry, when combined with high-resolution ground-based spectroscopy, rules out the possibility that the secondary component is a Galactic star. The limit on additional point sources is 3% of the brighter image for separations greater than 0.5" from the primary component and 5% of the brighter component for separations between 0.1" and 0.5". If the gravitational lens is an ordinary galaxy, it would not have been detected on the HST images.