METAL ABUNDANCES AND KINEMATICS OF A HIGH-REDSHIFT GALAXY OBTAINED WITH THE KECK TELESCOPE

We use the Keck 10 m telescope and its high-resolution echelle spectrometer (HIRES) to obtain accurate high-resolution spectra of a quasar to determine element abundances of a probable foreground young galaxy with redshift z = 2.309. Precise measurements of absorption lines lead to the first accurate abundance determinations on Zn, Cr, and Ni at large redshifts. We find that [Zn/H] = -1.55 +/- 0.11, while [Cr/H] = -1.79 +/- 0.10 and [Ni/H] = -2.13 +/- 0.08. The Zn abundance indicates low metallicity, while the Cr and Ni abundances are consistent with depletion of these elements onto grains. We also find [O/H] < 0.97. Therefore, the galaxy is more metal-deficient than the oldest disk stars in the Galaxy. The kinematic evidence is consistent with a thick disk of gas with rotation speed and radius comparable to the rotation speeds and radii of current luminous spiral galaxies. Therefore, a rotationally supported disk may be in place at z > 2.