We present the results of near-infrared spectroscopic observations for a sample of 12 star-forming galaxies at 1.0 < z < 1.5 , drawn from the DEEP2 Galaxy Redshift Survey .
H \beta , [ OIII ] , H \alpha , and [ NII ] emission-line fluxes are measured for these galaxies .
Application of the O 3 N 2 and N 2 strong-line abundance indicators implies average gas-phase oxygen abundances of 50 - 80 % solar .
We find preliminary evidence of luminosity-metallicity ( L - Z ) and mass-metallicity ( M - Z ) relationships within our sample , which spans from M _ { B } = -20.3 to -23.1 in rest-frame optical luminosity , and from 4 \times 10 ^ { 9 } to 2 \times 10 ^ { 11 } M _ { \odot } in stellar mass .
At fixed oxygen abundance , these relationships are displaced from the local ones by several magnitudes towards brighter absolute B -band luminosity and more than an order of magnitude towards larger stellar mass .
If individual DEEP2 galaxies in our sample follow the observed global evolution in the B -band luminosity function of blue galaxies between z \sim 1 and z \sim 0 ( Willmer et al . 2005 ) , they will fade on average by \sim 1.3 magnitudes in M _ { B } .
To fall on local ( L - Z ) and ( M - Z ) relationships , these galaxies must increase by a factor of 6 - 7 in M / L _ { B } between z \sim 1 and z \sim 0 , and by factor of two in both stellar mass and metallicity .
Such concurrent increases in stellar mass and metallicity are consistent with the expectations of a “ closed-box ” chemical evolution model , in which the effects of feedback and large-scale outflows are not important .
While K _ { s } < 20.0 z \sim 2 star-forming galaxies have similar [ NII ] /Ha ratios and rest-frame optical luminosities to those of the DEEP2 galaxies presented here , their higher M / L _ { B } ratios and clustering strengths indicate that they will experience different evolutionary paths to z \sim 0 .
Finally , emission line diagnostic ratios indicate that the z > 1 DEEP2 galaxies in our sample are significantly offset from the excitation sequence observed in nearby H II regions and SDSS emission-line galaxies .
This offset implies that physical conditions are different in the H II regions of distant galaxies hosting intense star formation , and may affect the chemical abundances derived from strong-line ratios for such objects .