A CORRELATION BETWEEN Lyα SPECTRAL LINE PROFILE AND REST-FRAME UV MORPHOLOGY

We explore the relationship between the spectral shape of the Ly alpha emission and the UV morphology of the host galaxy using a sample of 304 Ly alpha-emitting BVi-dropouts at 3 < z < 7 in the Great Observatories Origins Deep Survey and Cosmic Evolution Survey fields. Using our extensive reservoir of high-quality Keck DEIMOS spectra combined with Hubble Space Telescope WFC3 data, we measure the Ly alpha line asymmetries for individual galaxies and compare them to axial ratios measured from observed J-and H-band (restframe UV) images. We find that the Ly alpha skewness exhibits a large scatter at small elongation (a/b < 2), and this scatter decreases as the axial ratio increases. Comparison of this trend to radiative transfer models and various results from the literature suggests that these high-redshift Ly alpha emitters are not likely to be intrinsically round and symmetric disks, but they probably host galactic outflows traced by Ly alpha emitting clouds. The ionizing sources are centrally located, and the optical depth is a good indicator of the absorption and scattering events on the escape path of Ly alpha photons from the source. Our results find no evidence of evolution in Ly alpha asymmetry or axial ratio with look-back time.