We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at z ∼ 2.3. Targets are selected from the 3D-Hubble Space Telescope Treasury survey. The six detected galaxies have a mean [N II]λ6584/Hα ratio of 0.27 ± 0.01, with a small standard deviation of 0.05. This mean value is similar to that of UV-selected galaxies of the same mass. The mean gas-phase oxygen abundance inferred from the [N II]/Hα ratios depends on the calibration method, and ranges from 12+log(O/H)gas = 8.57 for the Pettini & Pagel calibration to 12+log(O/H)gas = 8.87 for the Maiolino et al. calibration. Measurements of the stellar oxygen abundance in nearby quiescent galaxies with the same number density indicate 12+log(O/H)stars = 8.95, similar to the gas-phase abundances of the z ∼ 2.3 galaxies if the Maiolino et al. calibration is used. This suggests that these high-redshift star forming galaxies may be progenitors of today's massive early-type galaxies. The main uncertainties are the absolute calibration of the gas-phase oxygen abundance and the incompleteness of the z ∼ 2.3 sample: the galaxies with detected Hα tend to be larger and have higher star formation rates than the galaxies without detected Hα, and we may still be missing the most dust-obscured progenitors.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science