A New High-Redshift L[CLC]y[/CLC]α Emitter: Possible Superwind Galaxy at [ITAL][CLC]z[/CLC][/ITAL] = 5.69

During the course of our deep optical imaging survey for Lyα emitters at z ≈ 5.7 in the field around the z = 5.74 quasar SDSSp J104433.04-012502.2, we found a candidate strong emission line source. Follow-up optical spectroscopy shows that the emission-line profile of this object is asymmetric, showing excess red wing emission. These properties are consistent with an identification of Lyα emission at a redshift of z = 5.687 ± 0.002. The observed broad line width (Δ v FWHM ≃ 340 km s -1 ) and excess red wing emission also suggest that this object hosts a galactic superwind.