The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is an untargeted spectroscopic survey that aims to measure the expansion rate of the Universe at z∼2.4 to 1% precision for both H(z) and DA(z). HETDEX is in the process of mapping in excess of one million Lyman Alpha emitting (LAE) galaxies and a similar number of lower-z galaxies as a tracer of the large-scale structure. The success of the measurement is predicated on the post-observation separation of galaxies with Lyα emission from the lower-z interloping galaxies, primarily [OII], with low contamination and high recovery rates. The Emission Line eXplorer (ELiXer) is the principal classification tool for HETDEX, providing a tunable balance between contamination and completeness as dictated by science needs. By combining multiple selection criteria, ELiXer improves upon the 20 Angstrom rest-frame equivalent width cut commonly used to distinguish LAEs from lower-z [OII] emitting galaxies. Despite a spectral resolving power, R ∼800, that cannot resolve the [OII] doublet, we demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1% accuracy. We estimate a contamination rate of Lyα by [OII] of 1.2% and a Lyα recovery rate of 99.1% using the default ELiXer configuration. These rates meet the HETDEX science requirements.
@article{arxiv.2301.01799,
title = {The HETDEX Survey: Emission Line Exploration and Source Classification},
author = {Dustin Davis and Karl Gebhardt and Erin Mentuch Cooper and Robin Ciardullo and Maximilian Fabricius and Daniel J. Farrow and John J. Feldmeier and Steven L. Finkelstein and Eric Gawiser and Caryl Gronwall and Gary J. Hill and Ulrich Hopp and Lindsay R. House and Donghui Jeong and Wolfram Kollatschny and Eiichiro Komatsu and Martin Landriau and Chenxu Liu and Shun Saito and Sarah Tuttle and Isak G. B. Wold and Gregory R. Zeimann and Yechi Zhang},
journal= {arXiv preprint arXiv:2301.01799},
year = {2023}
}