The Wide Field Imager Lyman-Alpha Search (WFILAS) for galaxies at redshift ~5.7 - I. A spatially compact Lyα emitting galaxy at redshift 5.721

We report the spectroscopic confirmation of a compact Ly α emitting galaxy at $z=5.721$. A FORS2 spectrum of the source shows a strong asymmetric line with a flux of $5\times 10^{-17}$ erg s -1 cm -2 , making it one of the brightest Ly α emitting galaxies at this redshift, and a line-of-sight velocity dispersion of 400 km s -1 . We also have a tentative detection of a second, narrower component that is redshifted by 400 km s -1 with respect to the main peak. A FORS2 image shows that the source is compact, with a FWHM of 0$\farcs$5, which corresponds to 3.2 kpc at this redshift. This source is a brighter example of J1236.8+6215 ([CITE], ApJ, 570, 92), another Ly α emit ting galaxy at $z\sim5.2$.