The HETDEX Survey: The Lyα Escape Fraction from 3D-HST Emission-Line Galaxies at z ∼ 2
Finkelstein, Steven L.; Schneider, Donald P.; Janowiecki, Steven; Wisotzki, Lutz; Blanc, Guillermo A.; Gebhardt, Karl; Gronwall, Caryl; Gawiser, Eric; Ciardullo, Robin; Mentuch Cooper, Erin; Farrow, Daniel J.; Bowman, William P.; Zeimann, Gregory R.; Weiss, Laurel H.; Jogee, Shardha; Hill, Gary J.
United States, Chile, Germany
Abstract
In this work, we measure the Lyα escape fraction of 935 [O III]-emitting galaxies between 1.9 < z < 2.35 by comparing stacked spectra from the Hubble Space Telescope/WFC3's near-IR grism to corresponding stacks from the Hobby-Eberly Telescope Dark Energy Experiment's Internal Data Release 2. By measuring the stacks' Hβ to Lyα ratios, we determine the Lyα escape fraction as a function of stellar mass, star-formation rate, internal reddening, size, and [O III]/Hβ ratio. We show that the escape fraction of Lyα correlates with a number of parameters, such as galaxy size, star-formation rate, and nebular excitation. However, we also demonstrate that most of these relations are indirect, and that the primary variables controlling the escape of Lyα are likely to be stellar mass and internal extinction. Overall, the escape of Lyα declines from ≳16% in galaxies with $\mathrm{log}M/{M}_{\odot }\lesssim 9$ to ≲1% for systems with $\mathrm{log}M/{M}_{\odot }\gtrsim 10$ , with the sample's mean escape fraction being ${6.0}_{-0.5 \% }^{+0.6 \% }$ .