Hubble Space Telescope Emission Line Galaxies At Z Similar To 2: The Ly Alpha Escape Fraction




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

Journal Title

Journal ISSN

Volume Title



We compare the H beta 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 Ly alpha 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 Ly alpha escape fraction below similar to 6%. We confirm this result by using stellar reddening to estimate the effective logarithmic extinction of the H beta emission line (c(H beta) = 0.5) and measuring both the H beta and Ly alpha luminosity functions in a similar to 100,000 Mpc(3) volume of space. We show that in our redshift window, the volumetric Ly alpha escape fraction is at most 4.4(-1.2)(+2.1)%, with an additional systematic similar to 25% uncertainty associated with our estimate of extinction. Finally, we demonstrate that the bulk of the epoch's star-forming galaxies have Ly alpha emission line optical depths that are significantly greater than that for the underlying UV continuum. In our predominantly [O-III] lambda 5007- selected sample of galaxies, resonant scattering must be important for the escape of Ly alpha photons.


LCSH Subject Headings


Ciardullo, Robin, Gregory R. Zeimann, Caryl Gronwall, Henry Gebhardt, Donald P. Schneider, Alex Hagen, A. I. Malz et al. "Hubble Space Telescope Emission Line Galaxies at z~ 2: The Ly? Escape Fraction." The Astrophysical Journal, Vol. 796, No. 1 (Nov., 2014): 64.