Fine-Structure FeII* Emission and Resonant MgII Emission in z = 1 Star-Forming Galaxies

TL;DR

This study investigates ultraviolet FeII* and MgII emission lines in 212 star-forming galaxies at z=1, revealing how their prevalence and strength relate to galaxy properties like dust, star formation, and stellar mass.

Contribution

It provides the first comprehensive analysis of FeII* and MgII emission in a large sample of z=1 galaxies, highlighting their dependence on galaxy characteristics and potential for probing circumgalactic gas.

Findings

FeII* emission is prevalent and modulated by dust attenuation.

MgII emission correlates strongly with specific star-formation rate.

Stronger MgII emission is associated with lower dust and stellar mass.

Abstract

We present a study of the prevalence, strength, and kinematics of ultraviolet FeII and MgII emission lines in 212 star-forming galaxies at z = 1 selected from the DEEP2 survey. We find FeII* emission in composite spectra assembled on the basis of different galaxy properties, indicating that FeII* emission is prevalent at z = 1. In these composites, FeII* emission is observed at roughly the systemic velocity. At z = 1, we find that the strength of FeII* emission is most strongly modulated by dust attenuation, and is additionally correlated with redshift, star-formation rate, and [OII] equivalent width, such that systems at higher redshifts with lower dust levels, lower star-formation rates, and larger [OII] equivalent widths show stronger FeII* emission. We detect MgII emission in at least 15% of the individual spectra and we find that objects showing stronger MgII emission have higher specific star-formation rates, smaller [OII] linewidths, larger [OII] equivalent widths, lower dust attenuations, and lower stellar masses than the sample as a whole. MgII 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 MgII emission. Future integral field unit observations of the spatial extent of FeII* and MgII 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.