The Lyman Continuum Escape Fraction of Emission Line-selected z ∼ 2.5 Galaxies Is Less Than 15%

Michael J. Rutkowski, Claudia Scarlata, Alaina Henry, Matthew Hayes, Vihang Mehta, Nimish Hathi, Seth Cohen, Rogier Windhorst, Anton M. Koekemoer, Harry I. Teplitz, Francesco Haardt, Brian Siana

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


Recent work suggests that strong emission line, star-forming galaxies (SFGs) may be significant Lyman continuum leakers. We combine archival Hubble Space Telescope broadband ultraviolet and optical imaging (F275W and F606W, respectively) with emission line catalogs derived from WFC3 IR G141 grism spectroscopy to search for escaping Lyman continuum (LyC) emission from homogeneously selected z ∼ 2.5 SFGs. We detect no escaping Lyman continuum from SFGs selected on [O ii] nebular emission (N = 208) and, within a narrow redshift range, on [O iii]/[O ii]. We measure 1σ upper limits to the LyC escape fraction relative to the non-ionizing UV continuum from [O ii] emitters, f esc ≲ 5.6%, and strong [O iii]/[O ii] > 5 ELGs, f esc ≲ 14.0%. Our observations are not deep enough to detect f esc ∼ 10% typical of low-redshift Lyman continuum emitters. However, we find that this population represents a small fraction of the star-forming galaxy population at z ∼ 2. Thus, unless the number of extreme emission line galaxies grows substantially to z 6, such galaxies may be insufficient for reionization. Deeper survey data in the rest-frame ionizing UV will be necessary to determine whether strong line ratios could be useful for pre-selecting LyC leakers at high redshift.

Original languageEnglish (US)
Article numberL27
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Jun 1 2017


  • galaxies: general
  • galaxies: star formation
  • ultraviolet: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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