PROPERTIES OF A HIGH-REDSHIFT GALAXY AT Z=4.4

We discuss the absorption properties of a high-redshift galaxy at z = 4.3829 identified as a damped Ly alpha system in the Keck spectrum of the quasar BRI 1202-0725 (z(em) = 4.7). This is at present the highest redshift damped Ly alpha system known, observed when the age of the u niverse was only 1 Gyr (q(0) = 0.5, H-0 = 50). Both the high redshift and low metallicity ([Fe/H] = -2.2) of the system indicate that it is an extremely young galaxy in an early stage of evolution. The relative elemental abundance patterns are consistent with extreme Population I I metallicities, providing evidence for enrichment by Type II supernov ae only. Kinematic evidence suggests that the absorbing galaxy may be a massive spiral. We discuss the implications of this result on theori es of galaxy formation. The Si Iv and C Iv absorption in the system ap pears unusually weak. Several plausible explanations are provided. We estimate T < 19.6 K for the cosmic microwave background radiation at z = 4.3829, which is consistent with the predicted temperature of 14.7 K from the big bang cosmology.