Near-Infrared Spectroscopy of Two Galaxies at z=2.3 and z=2.9: New Probes of Chemical and Dynamical Evolution at High Redshift
Abstract
This study presents Keck optical and infrared spectroscopy of the rest-frame ultraviolet and optical emission lines in two Lyman alpha emitting galaxies at z>2. These data provide insight on the evolution of fundamental galaxy scaling relations at early epochs, especially the luminosity-velocity and luminosity-metallicity relations. Lynx 2-9691 exhibits extended [O III] emission over a diameter of >28 kpc, reminiscent of the Lyman alpha nebulae discovered near Lyman-drop galaxies [Steidel et al 2000]. The ratios of strong nebular emission lines indicate sub-solar oxygen abundances in the range 8.2<12+log(O/H)<8.8 (Z = 0.25-0.95 Zsun). Interestingly, Galactic metal-rich globular clusters have similar metallicities, consistent with the idea that we could be seeing the formation of galaxies like the Milky Way at z3. The measured gas phase oxygen abundances are >4-10 times higher than the Z < 0.1 Zsun metallicities found in damped Lyman alpha (DLA) absorbers at similar redshifts, indicating that DLA systems trace different environments than the vigorously star-forming objects observed here. Star-forming galaxies at z3 are 2-4 magnitudes more luminous than local spiral galaxies of similar metallicity, and thus, are offset from the local luminosity-metallicity relation. Their kinematic linewidths are sigmav=65-130 km/s, making this sample 1-3 magnitudes more luminous than local galaxies of similar linewidth and mass. [Abridged]
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