Hubble imaging excludes cosmic string lens

Abstract

The galaxy image pair Capodimonte-Sternberg-Lens Candidate no. 1 (CSL-1) has been a leading candidate for a cosmic string lens. High quality imaging data from the Hubble Space Telescope presented here show that it is not a lens but a pair of galaxies. The galaxies show different orientations of their principal axes, not consistent with any lens model. We present a new direct test of the straight-string lens model, using a displaced difference of the image from itself to exclude CSL-1 at high confidence.