PHYSICAL PROPERTIES OF EMISSION-LINE GALAXIES AT z ∼ 2 FROM NEAR-INFRARED SPECTROSCOPY WITH MAGELLAN FIRE

We present results from near-infrared spectroscopy of 26 emission-line galaxies at z ~ 2.2 and z ~ 1.5 obtained with the Folded-port InfraRed Echellette (FIRE) spectrometer on the 6.5 m Magellan Baade telescope. Our FIRE follow-up spectroscopy (R ~ 5000) over 1.0-2.5 mu m permits detailed measurements of the physical properties of the z ~ 2 emission-line galaxies. Dust-corrected star formation rates for the sample range from ~5-100 M sub([middot in circle]) yr super(-1) with a mean of 29 M sub([middot in circle]) yr super(-1). We derive a median metallicity for the sample of 12 + log(O/H) = 8.34 or ~0.45 Z sub([middot in circle]). The average ionization parameter measured for the sample, log U approximately -2.5, is significantly higher than what is found for most star-forming galaxies in the local universe, but similar to the values found for other star-forming galaxies at high redshift. We speculate that the elevated nitrogen abundance could result from substantial numbers of Wolf-Rayet stars in starbursting galaxies at z ~ 2.