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 .
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 \alpha nebulae discovered near Lyman-drop galaxies [ Steidel et al .
2000 ] .
We estimate star formation rates of 59 M _ { \odot } ~ { } yr ^ { -1 } and 111 M _ { \odot } ~ { } 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 ~ { } Z _ { \odot } ) .
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 \sim 3 .
The measured gas phase oxygen abundances are > 4 - 10 times higher than the Z < 0.1 Z _ { \odot } metallicities found in damped Lyman \alpha ( 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 \sim 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 \sigma _ { v } = 65 - 130 km s ^ { -1 } , 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 .