A statistical study of multiply imaged systems in the lensing cluster abell 68

Johan Richard, Jean Paul Kneib, Eric Jullo, Giovanni Covone, Marceau Limousin, Richard Ellis, Daniel Stark, Kevin Bundy, Oliver Czoske, Harald Ebeling, Geneviève Soucail

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


We have carried out an extensive spectroscopic survey with the Keck and VLT telescopes, targeting lensed galaxies in the background of the massive cluster Abell 68. Spectroscopic measurements are obtained for 26 lensed images, including a distant galaxy at z = 5.4. Redshifts have been determined for 5 out of 7 multiple-image systems. Through a careful modeling of the mass distribution in the strongly lensed regime, we derive a mass estimate of 5.3 × 10 14 M within 500 kpc. Our mass model is then used to constrain the redshift distribution of the remaining multiply imaged and singly imaged sources. This enables us to examine the physical properties for a subsample of 7 Lyα emitters at 1.7 ≲ z ≲ 5.5, whose unlensed luminosities of ≃1041 ergs s-1 are fainter than similar objects found in blank fields. Of particular interest is an extended Lyα emission region surrounding a highly magnified source at z = 2.6, detected in VIMOS integral field spectroscopy data. The physical scale of the most distant lensed source at z = 5.4 is very small (<300 pc), similar to the lensed z ∼ 5.6 emitter reported by Ellis et al. in Abell 2218. New photometric data available for Abell 2218 allow for a direct comparison between these two unique objects. Our survey illustrates the practicality of using lensing clusters to probe the faint end of the z ~∼ 2-5 Lyα luminosity function in a manner that is complementary to blank-field narrowband surveys.

Original languageEnglish (US)
Pages (from-to)781-796
Number of pages16
JournalAstrophysical Journal
Issue number2 I
StatePublished - Jun 20 2007


  • Cosmology: observations
  • Galaxies: clusters: individual (A68)
  • Galaxies: high-redshift
  • Gravitational lensing

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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