Search

Full list of authors: Chaussidon, Edmond; Yeche, Christophe; Palanque-Delabrouille, Nathalie; Alexander, David M.; Yang, Jinyi; Ahlen, Steven; Bailey, Stephen; Brooks, David; Cai, Zheng; Chabanier, Solene; Davis, Tamara M.; Dawson, Kyle; de laMacorra, Axel; Dey, Arjun; Dey, Biprateep; Eftekharzadeh, Sarah; Eisenstein, Daniel J.; Fanning, Kevin; Font-Ribera, Andreu; Gaztanaga, Enrique; Gontcho, Satya Gontcho A.; Gonzalez-Morales, Alma X.; Guy, Julien; Herrera-Alcantar, Hiram K.; Honscheid, Klaus; Ishak, Mustapha; Jiang, Linhua; Juneau, Stephanie; Kehoe, Robert; Kisner, Theodore; Kovacs, Andras; Kremin, Anthony; Lan, Ting-Wen; Landriau, Martin; Le Guillou, Laurent; Levi, Michael E.; Magneville, Christophe; Martini, Paul; Meisner, Aaron M.; Moustakas, John; Munoz-Gutierrez, Andrea; Myers, Adam D.; Newman, Jeffrey A.; Nie, Jundan; Percival, Will J.; Poppett, Claire; Prada, Francisco; Raichoor, Anand; Ravoux, Corentin; Ross, Ashley J.; Schlafly, Edward; Schlegel, David; Tan, Ting; Tarle, Gregory; Zhou, Rongpu; Zhou, Zhimin; Zou, Hu.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., The Dark Energy Spectroscopic Instrument (DESI) survey will measure large-scale structures using quasars as direct tracers of dark matter in the redshift range 0.9 < z < 2.1 and using Lyα forests in quasar spectra at z > 2.1. We present several methods to select candidate quasars for DESI, using input photometric imaging in three optical bands (g, r, z) from the DESI Legacy Imaging Surveys and two infrared bands (W1, W2) from the Wide-field Infrared Survey Explorer. These methods were extensively tested during the Survey Validation of DESI. In this paper, we report on the results obtained with the different methods and present the selection we optimized for the DESI main survey. The final quasar target selection is based on a random forest algorithm and selects quasars in the magnitude range of 16.5 < r < 23. Visual selection of ultra-deep observations indicates that the main selection consists of 71% quasars, 16% galaxies, 6% stars, and 7% inconclusive spectra. Using the spectra based on this selection, we build an automated quasar catalog that achieves a fraction of true QSOs higher than 99% for a nominal effective exposure time of ∼1000 s. With a 310 deg−2 target density, the main selection allows DESI to select more than 200 deg−2 quasars (including 60 deg−2 quasars with z > 2.1), exceeding the project requirements by 20%. The redshift distribution of the selected quasars is in excellent agreement with quasar luminosity function predictions. © 2023. The Author(s). Published by the American Astronomical Society., A.D.M. was supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under award No. DE-SC0019022. T.W.L. was supported by the Ministry of Science and Technology (MOST 111-2112-M-002-015-MY3), the Ministry of Education, Taiwan (Yushan Young Scholar grant NTU-110VV007), National Taiwan University research grant (NTU-CC-111L894806), and NSF grant AST-1911140., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

We present a measurement of baryonic acoustic oscillations (BAO) from Lyman-$\alpha$ (Ly$\alpha$) absorption and quasars at an effective redshift $z=2.33$ using the complete extended Baryonic Oscillation Spectroscopic Survey (eBOSS). The sixteenth and final eBOSS data release (SDSS DR16) contains all data from eBOSS and its predecessor, the Baryonic Oscillation Spectroscopic Survey (BOSS), providing $210,005$ quasars with $z_{q}>2.10$ that are used to measure Ly$\alpha$ absorption. We measure the BAO scale both in the auto-correlation of Ly$\alpha$ absorption and in its cross correlation with $341,468$ quasars with redshift $z_{q}>1.77$. Apart from the statistical gain from new quasars and deeper observations, the main improvements over previous work come from more accurate modeling of physical and instrumental correlations and the use of new sets of mock data. Combining the BAO measurement from the auto- and cross-correlation yields the constraints of the two ratios $D_{H}(z=2.33)/r_{d} = 8.99 \pm 0.19$ and $D_{M}(z=2.33)/r_{d} = 37.5 \pm 1.1$, where the error bars are statistical. These results are within $1.5\sigma$ of the prediction of the flat-$\Lambda$CDM cosmology of Planck~(2016). The analysis code, \texttt{picca}, the catalog of the flux-transmission field measurements, and the $\Delta \chi^{2}$ surfaces are publicly available., Comment: 37 pages, 23 figures, Matches the published version by ApJ