The sextet arcs: A strongly lensed lyman break galaxy in the acs spectroscopic galaxy survey toward abell 1689

Brenda L. Frye, Dan Coe, David V. Bowen, Narciso Benítez, Tom Broadhurst, Puragra Guhathakurta, Garth Illingworth, Felipe Menanteau, Keren Sharon, Robert Lupton, Georges Meylan, Kerry Zekser, Gerhardt Meurer, Mairead Hurley

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


We present results of the HST Advanced Camera for Surveys spectroscopic ground-based redshift survey in the field of A1689. We measure 98 redshifts, increasing the number of spectroscopically confirmed objects sixfold. We present two spectra from this catalog of the Sextet Arcs, images that arise from a strongly lensed Lyman break galaxy (LBG) at a redshift of z = 3.038. Gravitational lensing by the cluster magnifies its flux by a factor of ∼ 16 and produces six separate images with a total r-band magnitude of r 625 = 21.7. The two spectra, each of which represents emission from different regions of the LBG, show H I and interstellar metal absorption lines at the systemic redshift. Significant variations are seen in the Lyα profile across a single galaxy, ranging from strong absorption to a combination of emission plus absorption. A spectrum of a third image close to the brightest arc shows Lyα emission at the same redshift as the LBG, arising from either another spatially distinct region of the galaxy or from a companion galaxy close to the LBG. Taken as a group, the Lyα equivalent width in these three spectra decreases with increasing equivalent width of the strongest interstellar absorption lines. We discuss how these variations can be used to understand the physical conditions in the LBG. Intrinsically, this LBG is faint, ∼0. 1L*, and is forming stars at a modest rate, ∼4 M yr-1. We also detect absorption-line systems toward the Sextet Arcs at z = 2.873 and z = 2.534. The latter system is seen across two of our spectra.

Original languageEnglish (US)
Pages (from-to)921-935
Number of pages15
JournalAstrophysical Journal
Issue number2 I
StatePublished - Aug 10 2007

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: Clusters: General
  • Galaxies: Clusters: Individual (A1689)
  • Galaxies: High-redshift
  • Gravitational lensing
  • Methods: Data analysis
  • Techniques: Spectroscopic


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