HETDEX Public Source Catalog 1-Stacking 50,000 Lyman Alpha Emitters

We describe the ensemble properties of the 1.9 < z < 3.5 Lyman alpha emitters (LAEs) found in the HETDEX survey's first public data release, HETDEX Public Source Catalog 1. Stacking the low-resolution (R ~ 800) spectra greatly increases the signal-to-noise ratio (S/N), revealing spectral features otherwise hidden by noise, and we show that the stacked spectrum is representative of an average member of the set. The flux-limited, Lyα S/N restricted stack of 50,000 HETDEX LAEs shows the ensemble biweight average z ~ 2.6 LAE to be a blue (UV continuum slope ~ -2.4 and E(B - V) < 0.1), moderately bright (M _UV ~ -19.7) star-forming galaxy with strong Lyα emission (log L _Lyα ~ 42.8 and W _λ (Lyα) ~ 114 Å), and potentially significant leakage of ionizing radiation. The rest-frame UV light is dominated by a young, metal-poor stellar population with an average age of 5-15 Myr and metallicity of 0.2-0.3 Z _⊙. ^∗ Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.