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arXiv · 1512.03063

HST Emission Line Galaxies at z ~ 2: Comparing Physical Properties of Lyman Alpha and Optical Emission Line Selected Galaxies

Alex Hagen·Gregory R. Zeimann·Christoph Behrens·Robin Ciardullo·Henry S. Grasshorn Gebhardt·Caryl Gronwall·Joanna S. Bridge·Derek B. Fox·Donald P. Schneider·Jonathan R. Trump·Guillermo A. Blanc·Yi-Kuan Chiang·Taylor S. Chonis·Steven L. Finkelstein·Gary J. Hill·Shardha Jogee·Eric Gawiser
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Abstract

We compare the physical and morphological properties of z ~ 2 Lyman-alpha emitting galaxies (LAEs) identified in the HETDEX Pilot Survey and narrow band studies with those of z ~ 2 optical emission line galaxies (oELGs) identified via HST WFC3 infrared grism spectroscopy. Both sets of galaxies extend over the same range in stellar mass (7.5 < logM < 10.5), size (0.5 < R < 3.0 kpc), and star-formation rate (~1 < SFR < 100). Remarkably, a comparison of the most commonly used physical and morphological parameters -- stellar mass, half-light radius, UV slope, star formation rate, ellipticity, nearest neighbor distance, star formation surface density, specific star formation rate, [O III] luminosity, and [O III] equivalent width -- reveals no statistically significant differences between the populations. This suggests that the processes and conditions which regulate the escape of Ly-alpha from a z ~ 2 star-forming galaxy do not depend on these quantities. In particular, the lack of dependence on the UV slope suggests that Ly-alpha emission is not being significantly modulated by diffuse dust in the interstellar medium. We develop a simple model of Ly-alpha emission that connects LAEs to all high-redshift star forming galaxies where the escape of Ly-alpha depends on the sightline through the galaxy. Using this model, we find that mean solid angle for Ly-alpha escape is 2.4+/-0.8 steradians; this value is consistent with those calculated from other studies.

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Alex Hagen, Gregory R. Zeimann, Christoph Behrens, Robin Ciardullo, Henry S. Grasshorn Gebhardt, Caryl Gronwall, Joanna S. Bridge, Derek B. Fox, Donald P. Schneider, Jonathan R. Trump, Guillermo A. Blanc, Yi-Kuan Chiang, Taylor S. Chonis, Steven L. Finkelstein, Gary J. Hill, Shardha Jogee, Eric Gawiser. 2015-12-09. HST Emission Line Galaxies at z ~ 2: Comparing Physical Properties of Lyman Alpha and Optical Emission Line Selected Galaxies. https://doi.org/10.3847/0004-637x%2F817%2F1%2F79

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