FINE-STRUCTURE Fe II* EMISSION AND RESONANT Mg II EMISSION INz∼ 1 STAR-FORMING GALAXIES

Abstract

We present a study of the prevalence, strength, and kinematics of ultraviolet Fe ii and Mg ii emission lines in 212 star-forming galaxies at z ∼ 1 selected from the DEEP2 survey. We find Fe ii* emission in composite spectra assembled on the basis of different galaxy properties, indicating that Fe ii* emission is common at z ∼ 1. In these composites, Fe ii* emission is observed at roughly the systemic velocity. At z ∼ 1, we find that the strength of Fe ii* emission is most strongly modulated by dust attenuation, and is additionally correlated with redshift, star formation rate, and [O ii] equivalent width, such that systems at higher redshifts with lower dust levels, lower star formation rates, and larger [O ii] equivalent widths show stronger Fe ii* emission. We detect Mg ii emission in at least 15% of the individual spectra and we find that objects showing stronger Mg ii emission have higher specific star formation rates, smaller [O ii] linewidths, larger [O ii] equivalent widths, lower dust attenuations, and lower stellar masses than the sample as a whole. Mg ii emission strength exhibits the strongest correlation with specific star formation rate, although we find evidence that dust attenuation and stellar mass also play roles in the regulation of Mg ii emission. Future integral field unit observations of the spatial extent of Fe ii* and Mg ii emission in galaxies with high specific star formation rates, low dust attenuations, and low stellar masses will be important for probing the morphology of circumgalactic gas.