Target Selection and Validation of DESI Emission Line Galaxies

By A. Raichoor, John Moustakas, J. Newman, T. Karim, S. Ahlen, Shadab Alam, S. Bailey, D. Brooks, K. Dawson, A. de la Macorra and 42 more. Astronomical Journal, 2022

144 citations recorded by the source corpus.

The Dark Energy Spectroscopic Instrument (DESI) will precisely constrain cosmic expansion and the growth of structure by collecting ∼40 million extragalactic redshifts across ∼80% of cosmic history and one-third of the sky. The Emission Line galaxy (ELG) sample, which will comprise about one-third of all DESI tracers, will be used to probe the universe over the 0.6 < z < 1.6 range, including the 1.1 < z < 1.6 range, which is expected to provide the tightest constraints. We present the target selection for the DESI Survey Validation (SV) and Main Survey ELG samples, which relies on the imaging of the Legacy Surveys. The Main ELG selection consists of a g-band magnitude cut and a (g − r) versus (r − z) color box, while the SV selection explores extensions of the Main selection boundaries. The Main ELG sample is composed of two disjoint subsamples, which have target densities of about 1940 deg−2 and 460 deg−2, respectively. We first characterize their photometric properties and density variations across the footprint. We then analyze the DESI spectroscopic data that have been obtained from 2020 December to 2021 December in the SV and Main Survey. We establish a preliminary criterion for selecting reliable redshifts, based on the [O ii] flux measurement, and assess its performance. Using this criterion, we are able to present the spectroscopic efficiency of the Main ELG selection, along with its redshift distribution. We thus demonstrate that the Main selection 1940 deg−2 subsample alone should provide 400 deg−2 and 460 deg−2 reliable redshifts in the 0.6 < z < 1.1 and the 1.1 < z < 1.6 ranges, respectively.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/618ab71e596c4925b5d69e222523dd30413f9ce0

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Citations in the corpus

Survey Operations for the Dark Energy Spectroscopic Instrument (2023, methodology): “The primary targets are quasars (Yèche et al. 2020; Chaussidon et al. 2023), emission line galaxies with 0.6 < z < 1.6 (Raichoor et al. 2020, 2023), luminous red galaxies with 0.4 < z < 1 (Zhou et al. 2020, 2023), bright galaxies with z < 0.4 (Ruiz-Macias et al. 2020; Hahn et al. 2022), and stars…”
The Early Data Release of the Dark Energy Spectroscopic Instrument (2023, methodology): “Following Raichoor et al. ( 2023 ) , this information is combined with the Δ χ 2 obtained from the redshift ﬁ tting pipeline between the best and next-best-ﬁ t redshifts ( the quantity DELTACHI2 in Section 3.1.3 ) to determine a criterion, 4 ) .”
Data Release 1 of the Dark Energy Spectroscopic Instrument (2025, unknown): “…( 0 < z < 0.6; O. Ruiz-Macias et al. 2020; C. Hahn et al. 2023 ) ; luminous red galaxies ( LRGs; 0.4 < z < 1.1; R. Zhou et al. 2020, 2023 ) ; emission-line galaxies ( ELGs; 0.6 < z < 1.6; A. Raichoor et al. 2020, 2023 ) ; and QSOs ( 0.9 < z < 4; C. Yèche et al. 2020; E. Chaussidon et al. 2023 ) .”
Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument (2023, methodology): “A full description of the final target selection algorithms for the LRG, ELG, and quasar samples can be found in accompanying papers by Zhou et al. (2023), Raichoor et al. (2023a), and Chaussidon et al. (2023), respectively.”
The Optical Corrector for the Dark Energy Spectroscopic Instrument (2023, background): “The survey will observe four classes of galactic targets: Bright Galaxy Survey targets (BGS, Hahn et al. 2022), luminous red galaxies (LRG, Zhou et al. 2023), emission line galaxies (ELG, Raichoor et al. 2023), and quasi-stellar objects (QSO, Chaussidon et al. 2023).”
The DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation (2022, background): “Occasionally, targets whose redshifts were unsuccessfully measured are reobserved but reassigned lower priority (see Raichoor et al. 2023 for details).”