The HETDEX Survey: The Ly alpha Escape Fraction from 3D-HST Emission-Line Galaxies at z similar to 2

In this work, we measure the Ly alpha 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' H beta to Ly alpha ratios, we determine the Ly alpha escape fraction as a function of stellar mass, star-formation rate, internal reddening, size, and [O III]/H beta ratio. We show that the escape fraction of Ly alpha 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 Ly alpha are likely to be stellar mass and internal extinction. Overall, the escape of Ly alpha declines from greater than or similar to 16% in galaxies with logM/M-circle dot less than or similar to 9 to less than or similar to 1% for systems with logM/M-circle dot greater than or similar to 10, with the sample's mean escape fraction being 6.0(-0.5%)(+0.6%).