Abstract: Lyman-α (λ1216; Lyα) emission from star-forming galaxies allow us to understand how the young Universe got reionised.  At later cosmological epochs these galaxies can shed light on the elusive nature of dark energy.  Both applications require a firm understanding of the physics that govern the emergence or disapearance of Lyα emission from a galaxy.  Here I will relate kinematical mesurements of the ionised gas-phase to Lyα escape fractions, Lyα equivalent widths, and Lyα luminosities.  The study uses Calar-Alto PMAS observations of 42 galaxies of the "Extended Lyα Reference Sample".  For these low-redshift galaxies Lyα measurements were obtainted by ultraviolet imaging observations with the Hubble Space Telescope.  As a main result it emerges that galaxies with EW(Lyα) ≥ 20 Å show systematically higher ionised gasvelocity dispersions, σ₀, than galaxies below the canonical Lyα emitter threshold.  Quantifying the relative importance
of galaxy kinematics with respect to other galaxy parameters reveals that σ₀ is of dominant importance in regulating EW(Lyα).  Moreover, σ₀ is found of similar importance as nebular extinction, gas covering fraction, and ionising photon production efficiency for regulating the Lyα escape fraction.  I will argue that the high σ₀ values are related to a highly turbulent medium driven by feedback from the youngest starbursts.
Theoretically it is expected that turbulent gas can promote Lyα escape.  These results hint at short duty cycles during starburst events for the Lyα emitting phase of a galaxy.