Keck Observations of the Most Distant Galaxy: 8C 1435+63 at Z = 4.25

We report on Keck observations and confirm the redshift of the most distant galaxy known: 8C 1435 + 63 at z = 4.25. The spectrum shows a Strong Lyα line, a Lyα forest continuum break and a continuum break at λ_rest_ = 912 A. The Lyα emission is spatially extended and roughly aligned with the radio source. The galaxy shows a double structure in the I-band (λ_rest_~1500A) which is aligned with the radio axis; the two I-band components spatially coincide with the nuclear and southern radio components. Some fraction of the I-band emission could be due to a nonthermal process such as inverse Compton scattering. In the K-band (λ_rest_ 4200 A), which may be dominated by starlight, the galaxy has a very low surface brightness, diffuse morphology. The K morphology shows little relationship to the radio source structure, although the major axis of the K emission is elongated roughly in the direction of the radio source axis. The galaxian continuum is very red (I- K > 4) and if the K continuum is due to starlight, implies a formation redshift of z_f_ > 5. We speculate that this galaxy may be the progenitor of a present-day cD galaxy.