Evidence of Fermi acceleration of Ly alpha in the radio galaxy 1243+036

The high-redshift radio galaxy 1243+036 (z = 36)presents an asymmetric Ly a lpha profile of FWHM 1550 km s(-1) as measured by van Ojik et al. We propos e that the blue asymmetry in the Ly alpha profile is not due to narrow abso rption dips but consists of narrow emission peaks. We interpret the blueshi fted peaks near -1130, -850, and -550 km s(-1) (relative to the peak of ful l profile) as being the result of Fermi acceleration of Ly alpha produced b y jet-induced star formation in the wake of a 300 km s(-1) shock. This shoc k would be caused by the deflection of the radio jet at the observed positi on of the radio bend which also coincides spatially with the excess Ly alph a emission reported by van Ojik et al.