Other
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aas...19713506k&link_type=abstract
American Astronomical Society, 197th AAS Meeting, #135.06; Bulletin of the American Astronomical Society, Vol. 33, p.723
Other
Scientific paper
This study presents Keck optical and infrared spectroscopy of the rest-frame ultraviolet and optical emission lines in two Lyman α 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. Spectral diagnostics suggest that the Coup Fourré Galaxy at z=2.3 [CFg; Lowenthal et al. 1991] and Lynx 2-9691, a serendipitously-discovered, luminous Lyman-drop galaxy at z=2.9, are star-forming galaxies without active nuclei. Lynx 2-9691 exhibits extended [O III] emission over a diameter of >28 kpc, reminiscent of the Lyman α nebulae discovered near Lyman-drop galaxies [Steidel et al. 2000]. We estimate star formation rates of 59 Msun yr-1 and 111 Msun yr-1, respectively, from Balmer recombination line luminosities, 2-3 times higher than inferred from the ultraviolet continuum. 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 z ~3. The measured gas phase oxygen abundances are >4-10 times higher than the Z < 0.1 Zsun metallicities found in damped Lyman α (DLA) absorbers at similar redshifts, indicating that DLA systems trace fundamentally different environments than the vigorously star-forming objects observed here. If this intense star formation activity represents the dominant formation episodes for stars in today's spiral bulges or ellipticals, then the evolved descendants in the local universe should exhibit similarly sub-solar metallicities in their dominant stellar populations which formed 8-10 Gyr ago. When these new data are combined with a sample of four other high-redshift spectroscopic results from the literature, we find that star-forming galaxies at z ~3 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 σ v=65-130 km/s, making this sample 1-3 magnitudes more luminous than local galaxies of similar linewidth and mass. Less luminous Lyman-drop galaxies need to be studied to see if these deviations are universal or apply to only the most luminous high-redshift galaxies.
Kobulnicky Henry A.
Koo David C.
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