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Title: ODIN: Spectroscopic Validation of Lyα-emitting Galaxy Samples with DESI

Abstract: The One-hundred-deg(2) DECam Imaging in Narrowbands (ODIN) survey is conducting the widest-field deep narrowband (NB) imaging of the equatorial and southern skies. ODIN uses three custom-built NB filters that sample Ly alpha-emitting galaxies (LAEs) within thin cosmic slices centered at z = 2.4, 3.1, and 4.5. In this work, we utilize extensive DESI spectroscopy of ODIN-selected galaxies in the COSMOS and XMM-LSS fields to validate our LAE selection. Exposures of 2-4 hr with DESI yielded redshift confirmation of 3075 ODIN LAE candidates with NB magnitudes brighter than 26 mag. Restricting to objects that yield high-confidence redshifts, the confirmation rates are (93%, 96%, 92%) at z = (2.4, 3.1, 4.5). The primary contaminants consist of active galactic nuclei at the expected Ly alpha-redshift range and lower redshifts (C iv, C iii]), with the remainder being star-forming galaxies ([O ii] and [O iii]). We find minimal contamination from [O ii] emitters in our sample (less than or similar to 1%), implying that our rest-frame equivalent width (REW) > 20 & Aring; NB excess photometry requirement is sufficient to remove them.

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