The HETDEX Survey Emission-line Exploration and Source Classification

April 2023 • 2023ApJ...946...86D

Authors • Davis, Dustin • Gebhardt, Karl • Cooper, Erin Mentuch • Ciardullo, Robin • Fabricius, Maximilian • Farrow, Daniel J. • Feldmeier, John J. • Finkelstein, Steven L. • Gawiser, Eric • Gronwall, Caryl • Hill, Gary J. • Hopp, Ulrich • House, Lindsay R. • Jeong, Donghui • Kollatschny, Wolfram • Komatsu, Eiichiro • Landriau, Martin • Liu, Chenxu • Saito, Shun • Tuttle, Sarah • Wold, Isak G. B. • Zeimann, Gregory R. • Zhang, Yechi

Abstract • 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 D _A (z). HETDEX is in the process of mapping in excess of one million Lyα 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 [O II], 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 Å rest-frame equivalent width cut commonly used to distinguish LAEs from lower-z [O II] emitting galaxies. Despite a spectral resolving power, R ~ 800, that cannot resolve the [O II] doublet, we demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1% accuracy. We estimate a contamination rate of Lyα by [O II] of 1.2% and a Lyα recovery rate of 99.1% using the default ELiXer configuration. These rates meet the HETDEX science requirements. ^* Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.

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• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2023ApJ...946...86D
• PREPRINT http://arxiv.org/abs/2301.01799
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2023ApJ...946...86D
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2023ApJ...946...86D
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2023ApJ...946...86D
• DATA https://irsa.ipac.caltech.edu/bibdata/2023/D/2023ApJ...946...86D.html
• ELECTR https://doi.org/10.3847%2F1538-4357%2Facb0ca