2020MNRAS.492.1778M

The observed properties of the Lyman-α (Ly α) emission line are a powerful probe of neutral gas in and around galaxies. We present spatially resolved Ly α spectroscopy with VLT/MUSE targeting VR7, a UV-luminous galaxy at z = 6.532 with moderate Ly α equivalent width (EW₀ ≃ 38 Å). These data are combined with deep resolved [CII]_158µm spectroscopy obtained with ALMA and UV imaging from HST and we also detect UV continuum with MUSE. Ly α emission is clearly detected with S/N ≃ 40 and FWHM of 374 km s^–1. Ly α and [C II] are similarly extended beyond the UV, with effective radius r_eff = 2.1 ± 0.2 kpc for a single exponential model or r_ eff, Lyα, halo_ = 3.45^+1.08_–0.87 kpc when measured jointly with the UV continuum. The Ly α profile is broader and redshifted with respect to the [C II] line (by 213 km s^–1), but there are spatial variations that are qualitatively similar in both lines and coincide with resolved UV components. This suggests that the emission originates from two components with plausibly different H I column densities. We place VR7 in the context of other galaxies at similar and lower redshift. The Ly α halo scale length is similar at different redshifts and velocity shifts with respect to the systemic are typically smaller. Overall, we find little indications of a more neutral vicinity at higher redshift. This means that the local (∼10 kpc) neutral gas conditions that determine the observed Ly α properties in VR7 resemble the conditions in post-reionization galaxies.