Spectroscopic confirmation of faint lyman break galaxies near redshift five in the hubble ultra deep field

James E. Rhoads, Sangeeta Malhotra, Norbert Pirzkal, Mark Dickinson, Seth Cohen, Norman Grogin, Nimish Hathi, Chun Xu, Ignacio Ferreras, Caryl Gronwall, Anton Koekemoer, Martin Kümmel, Gerhardt Meurer, Nino Panagia, Anna Pasquali, Russell Ryan, Amber Straughn, Jeremy Walsh, Rogier A. Windhorst, Hao Jing Yan

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


We present the faintest spectroscopically confirmed sample of z 5 Lyman break galaxies (LBGs) to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the Grism ACS Program for Extragalactic Science (GRAPES) and Probing Evolution and Reionization Spectroscopically (PEARS) projects, using the G800L grism on the Hubble Space Telescope Advanced Camera for Surveys. We report here confirmations of 39 galaxies, preselected as candidate LBGs using photometric selection criteria. We compare a "traditional" V-dropout selection, based on the work of Giavalisco et al., to a more liberal one (with V - i > 0.9), and find that the traditional criteria are about 64% complete and 81% reliable. We also study the Lyα emission properties of our sample. We find that Lyα emission is detected in 1/4 of the sample, and that the liberal V-dropout color selection includes 55% of previously published line-selected Lyα sources. Finally, we examine our stacked two-dimensional spectra. We demonstrate that strong, spatially extended (1″) Lyα emission is not a generic property of these LBGs, but that a modest extension of the Lyα photosphere (compared to the starlight) may be present in those galaxies with prominent Lyα emission.

Original languageEnglish (US)
Pages (from-to)942-949
Number of pages8
JournalAstrophysical Journal
Issue number1
StatePublished - 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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