THE LY-ALPHA H-ALPHA RATIO IN HIGH-REDSHIFT RADIO GALAXIES

We present the first spectroscopic detections of H-alpha emission from radio galaxies at z > 2. Narrow H-alpha emission has been detected at the 5 sigma-level in the radio galaxies B3 0731 + 438 at z = 2.43 and MRC 0406 - 244 at z = 2.44. After correcting for foreground Galactic extinction we derive Lyman-alpha/H-alpha ratios of 4.7 and 3.5, implying E(B - V) = 0.1 +/- 0.06(3-sigma) and E(B - V) = 0.13 +/- 0.08 for the two galaxies. These should be regarded as upper limits to the reddening since multiple scatterings may contribute to the destruction of Ly-alpha. The H-alpha + [N II] emission lines contribute 20% +/- 6% (0731 + 438) and 12% +/- 4% (0406 - 244) of the broad-band fluxes at K. The effect of the implied reddening and emission-line contributions result in an observed frame r - K color which is bluer by 0.7-0.8 mag, but have a negligible effect on M(K). Such a large change in the spectral energy distribution can have a substantial impact on the inferred ages and star-formation histories.