A very bright, highly magnified Lyman-break galaxy at z=3.07
  We report the discovery using Hubble Space Telescope imaging and Keck spectroscopy of a very bright, highly magnified (~30*) Lyman Break Galaxy (LBG) at z=3.07 in the field of the massive z=0.33 cluster MACSJ2135.2-0102. The system comprises two high-surface brightness arcs with a maximum extent of 3", bracketing a central object which we identify as a massive early-type galaxy at z=0.73. We construct a lens model which reproduces the main features of the system using a combination of a galaxy-scale lens and the foreground cluster. We show that the morphological, spectral and photometric properties of the arcs are consistent with them arising from the lensing of a single ~L* LBG. The most important feature of this system is that the lensing magnification results in an apparent magnitude of r=20.3, making this one of the brightest LBGs known. Such a high magnification provides the opportunity of obtaining very high signal to noise (and potentially spatially resolved) spectroscopy of a high redshift galaxy to study its physical properties. We present initial imaging and spectroscopy demonstrating the basic properties of the system and discuss the opportunities for future observations. 
Ian Smail (ICC, Durham), A.M. Swinbank (ICC), J. Richard (CIT), H.   Ebeling (IfA), J.-P. Kneib (LAM), A.C. Edge (ICC), D. S...