Hubble space telescope emission line galaxies at z ∼ 2: The Lyα escape fraction

Robin Ciardullo, Gregory R. Zeimann, Caryl Gronwall, Henry Gebhardt, Donald P. Schneider, Alex Hagen, A. I. Malz, Guillermo A. Blanc, Gary J. Hill, Niv Drory, Eric Gawiser

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Abstract

We compare the Hβ line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Lyα from the HETDEX Pilot Survey and narrow-band imaging. By examining the line ratios of 73 galaxies, we show that most star-forming systems at this epoch have a Lyα escape fraction below ∼6%. We confirm this result by using stellar reddening to estimate the effective logarithmic extinction of the Hβ emission line (c = 0.5) and measuring both the Hβ and Lyα luminosity functions in a ∼100, 000 Mpc3 volume of space. We show that in our redshift window, the volumetric Lyα escape fraction is at most , with an additional systematic ∼25% uncertainty associated with our estimate of extinction. Finally, we demonstrate that the bulk of the epoch's star-forming galaxies have Lyα emission line optical depths that are significantly greater than that for the underlying UV continuum. In our predominantly [O III] λ5007-selected sample of galaxies, resonant scattering must be important for the escape of Lyα photons.

Original languageEnglish (US)
Article number64
JournalAstrophysical Journal
Volume796
Issue number1
DOIs
StatePublished - Nov 20 2014

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Ciardullo, R., Zeimann, G. R., Gronwall, C., Gebhardt, H., Schneider, D. P., Hagen, A., Malz, A. I., Blanc, G. A., Hill, G. J., Drory, N., & Gawiser, E. (2014). Hubble space telescope emission line galaxies at z ∼ 2: The Lyα escape fraction. Astrophysical Journal, 796(1), [64]. https://doi.org/10.1088/0004-637X/796/1/64