Composite Spectra of Emission-line Galaxies from eBOSS

The eBOSS survey is obtaining spectra of about 200,000 emission line galaxies (ELGs) at redshifts z>0.6, providing a unique rich dataset of rest-frame near-UV spectroscopy for astrophysical applications. For target selection purposes, the ELG pilot survey observed about 12,000 ELGs, among which about 8,600 are at 0.6Zhu et al. (2015) presented the composite spectra of these galaxies, and in particular, investigated the blueshifted resonant absorption lines (Fe II, Mg II) and non-resonant emission lines (Fe II*) in the NUV; these are the signatures of ubiquitous galactic-scale outflows associated with star formation activities. Because the composite spectra are of great interest to the community, here we make them publicly available as a value-added product.