(ACCEPTED FOR PUBLICATION IN The Astrophysical Journal; AUGUST 5, 2013) Preprint typeset using LATEX style emulateapj v. 04/20/08 THE SPECTRALLY RESOLVED Lyα EMISSION OF THREE Lyα-SELECTED FIELD GALAXIES AT z ∼ 2.4 FROM THE HETDEX PILOT SURVEY*

We present new results on the spectrally resolved Lyα emission of three Lyα emitting field galaxies at z ∼ 2.4 with high Lyα equivalent width (> 100 Å) and Lyα luminosity ( ∼ 1043 erg s−1). At 120 km s−1 (FWHM) spectral resolution, the prominent double-peaked Lyα profile straddles the systemic velocity, where the veloc-ity zero-point is determined from spectroscopy of the galaxies ’ rest-frame optical nebular emission lines. The average velocity offset from systemic of the stronger redshifted emission component for our sample is 176 km s−1 while the average total separation between the redshifted and main blueshifted emission components is 380 km s−1. These measurements are a factor of ∼ 2 smaller than for UV continuum-selected galaxies that show Lyα in emission with lower Lyα equivalent width. We compare our Lyα spectra to the predicted line profiles of a spherical “expanding shell ” Lyα radiative transfer grid that models large-scale galaxy outflows. Specifically blueward of the systemic velocity where two galaxies show a weak, highly blueshifted (by ∼ 1000 km s−1) tertiary emission peak, the model line profiles are a relatively poor representation of the observed spectra. Since the neutral gas column density has a dominant influence over the shape of the Lyα line profile, we caution against equating the observed Lyα velocity offset with a physical outflow velocity, especially at lower spectral resolution where the unresolved Lyα velocity offset is a convoluted function of several degenerate parameters