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Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiere, We describe the Milky Way Survey (MWS) that will be undertaken with the Dark Energy Spectroscopic Instrument (DESI) on the Mayall 4 m telescope at the Kitt Peak National Observatory. Over the next 5 yr DESI MWS will observe approximately seven million stars at Galactic latitudes ∣b∣ > 20°, with an inclusive target selection scheme focused on the thick disk and stellar halo. MWS will also include several high-completeness samples of rare stellar types, including white dwarfs, low-mass stars within 100 pc of the Sun, and horizontal branch stars. We summarize the potential of DESI to advance understanding of the Galactic structure and stellar evolution. We introduce the final definitions of the main MWS target classes and estimate the number of stars in each class that will be observed. We describe our pipelines for deriving radial velocities, atmospheric parameters, and chemical abundances. We use ≃500,000 spectra of unique stellar targets from the DESI Survey Validation program (SV) to demonstrate that our pipelines can measure radial velocities to ≃1 km s−1 and [Fe/H] accurate to ≃0.2 dex for typical stars in our main sample. We find the stellar parameter distributions from ≈100 deg2 of SV observations with ≳90% completeness on our main sample are in good agreement with expectations from mock catalogs and previous surveys, This equipment was funded by MoE, NSTC, and National Tsing Hua University. C.A.P. acknowledges financial support from the Spanish Ministry of Science and Innovation (MICINN) projects AYA2017-86389-P and PID2020-117493GB-I00. C.J.M. acknowledges financial support from Imperial College London through an Imperial College Research Fellowship grant. M.V. and L.B.e.S. acknowledge support from NASA-ATP award 80NSSC20K0509. The work of A.D. and J.N. is supported by NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. T.S.L. acknowledges financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) through grant RGPIN-2022-04794. B.T. G. was supported by grant ST/T000406/1 from the Science and Technology Facilities Council (STFC). This project has received funding from the European Research Council under the European Unionʼs Horizon 2020 research and innovation program (grant agreement No. 101020057). This research made use of computing time available on the high-performance computing system at the Instituto de Astrofisica de Canarias

Full list of authors: Myers, Adam D.; Moustakas, John; Bailey, Stephen; Weaver, Benjamin A.; Cooper, Andrew P.; Forero-Romero, Jaime E.; Abolfathi, Bela; Alexander, David M.; Brooks, David; Chaussidon, Edmond; Chuang, Chia-Hsun; Dawson, Kyle; Dey, Arjun; Dey, Biprateep; Dhungana, Govinda; Doel, Peter; Fanning, Kevin; Gaztanaga, Enrique; Gontcho, Satya Gontcho; Gonzalez-Morales, Alma X.; Hahn, ChangHoon; Herrera-Alcantar, Hiram K.; Honscheid, Klaus; Ishak, Mustapha; Karim, Tanveer; Kirkby, David; Kisner, Theodore; Koposov, Sergey E.; Kremin, Anthony; Lan, Ting-Wen; Landriau, Martin; Lang, Dustin; Levi, Michael E.; Magneville, Christophe; Napolitano, Lucas; Martini, Paul; Meisner, Aaron; Newman, Jeffrey A.; Palanque-Delabrouille, Nathalie; Percival, Will; Poppett, Claire; Prada, Francisco; Raichoor, Anand; Ross, Ashley J.; Schlafly, Edward F.; Schlegel, David; Schubnell, Michael; Tan, Ting; Tarle, Gregory; Wilson, Michael J.; Yeche, Christophe; 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., In 2021 May, the Dark Energy Spectroscopic Instrument (DESI) began a 5 yr survey of approximately 50 million total extragalactic and Galactic targets. The primary DESI dark-time targets are emission line galaxies, luminous red galaxies, and quasars. In bright time, DESI will focus on two surveys known as the Bright Galaxy Survey and the Milky Way Survey. DESI also observes a selection of "secondary" targets for bespoke science goals. This paper gives an overview of the publicly available pipeline (desitarget) used to process targets for DESI observations. Highlights include details of the different DESI survey targeting phases, the targeting ID (TARGETID) used to define unique targets, the bitmasks used to indicate a particular type of target, the data model and structure of DESI targeting files, and examples of how to access and use the desitarget code base. This paper will also describe "supporting" DESI target classes, such as standard stars, sky locations, and random catalogs that mimic the angular selection function of DESI targets. The DESI target-selection pipeline is complex and sizable; this paper attempts to summarize the most salient information required to understand and work with DESI targeting data. © 2023. The Author(s). Published by the American Astronomical Society., A.D.M. and J.M. were supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Award Numbers DE-SC0019022 and DE-SC0020086. A.P.C. is supported by a Taiwan Ministry of Education Yushan Fellowship and Taiwan Ministry of Science and Technology grant No. 109-2112-M-007-011-MY3. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under Contract No. DEAC0205CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under Contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institutions., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

Full list of authors: Abareshi, B.; Aguilar, J.; Ahlen, S.; Alam, Shadab; Alexander, David M.; Alfarsy, R.; Allen, L.; Allende Prieto, C.; Alves, O.; Ameel, J.; Armengaud, E.; Asorey, J.; Aviles, Alejandro; Bailey, S.; Balaguera-Antolinez, A.; Ballester, O.; Baltay, C.; Bault, A.; Beltran, S. F.; Benavides, B.; BenZvi, S.; Berti, A.; Besuner, R.; Beutler, Florian; Bianchi, D.; Blake, C.; Blanc, P.; Blum, R.; Bolton, A.; Bose, S.; Bramall, D.; Brieden, S.; Brodzeller, A.; Brooks, D.; Brownewell, C.; Buckley-Geer, E.; Cahn, R. N.; Cai, Z.; Canning, R.; Capasso, R.; Carnero Rosell, A.; Carton, P.; Casas, R.; Castander, F. J.; Cervantes-Cota, J. L.; Chabanier, S.; Chaussidon, E.; Chuang, C.; Circosta, C.; Cole, S.; Cooper, A. P.; da Costa, L.; Cousinou, M-C; Cuceu, A.; Davis, T. M.; Dawson, K.; De la Cruz-Noriega, R.; de la Macorra, A.; de Mattia, A.; Della Costa, J.; Demmer, P.; Derwent, M.; Dey, A.; Dey, B.; Dhungana, G.; Ding, Z.; Dobson, C.; Doel, P.; Donald-McCann, J.; Donaldson, J.; Douglass, K.; Duan, Y.; Dunlop, P.; Edelstein, J.; Eftekharzadeh, S.; Eisenstein, D. J.; Enriquez-Vargas, M.; Escoffier, S.; Evatt, M.; Fagrelius, P.; Fan, X.; Fanning, K.; Fawcett, V. A.; Ferraro, S.; Ereza, J.; Flaugher, B.; Font-Ribera, A.; Forero-Romero, J. E.; Frenk, C. S.; Fromenteau, S.; Gansicke, B. T.; Garcia-Quintero, C.; Garrison, L.; Gaztanaga, E.; Gerardi, F.; Gil-Marin, H.; Gontcho, S. Gontcho A.; Gonzalez-Morales, Alma X.; Gonzalez-de-Rivera, G.; Gonzalez-Perez, V; Gordon, C.; Graur, O.; Green, D.; Grove, C.; Gruen, D.; Gutierrez, G.; Guy, J.; Hahn, C.; Harris, S.; Herrera, D.; Herrera-Alcantar, Hiram K.; Honscheid, K.; Howlett, C.; Huterer, D.; Irsic, V; Ishak, M.; Jelinsky, P.; Jiang, L.; Jimenez, J.; Jing, Y. P.; Joyce, R.; Jullo, E.; Juneau, S.; Karacayli, N. G.; Karamanis, M.; Karcher, A.; Karim, T.; Kehoe, R.; Kent, S.; Kirkby, D.; Kisner, T.; Kitaura, F.; Koposov, S. E.; Kovacs, A.; Kremin, A.; Krolewski, Alex; L'Huillier, B.; Lahav, O.; Lambert, A.; Lamman, C.; Lan, Ting-Wen; Landriau, M.; Lane, S.; Lang, D.; Lange, J. U.; Lasker, J.; Le Guillou, L.; Leauthaud, A.; Suu, A. Le Van; Levi, Michael E.; Li, T. S.; Magneville, C.; Manera, M.; Manser, Christopher J.; Marshall, B.; Martini, Paul; McCollam, W.; McDonald, P.; Meisner, Aaron M.; Mena-Fernandez, J.; Meneses-Rizo, J.; Mezcua, M.; Miller, T.; Miquel, R.; Montero-Camacho, P.; Moon, J.; Moustakas, J.; Mueller, E.; Munoz-Gutierrez, Andrea; Myers, Adam D.; Nadathur, S.; Najita, J.; Napolitano, L.; Neilsen, E.; Newman, Jeffrey A.; Nie, J. D.; Ning, Y.; Niz, G.; Norberg, P.; Noriega, Hernan E.; O'Brien, T.; Obuljen, A.; Palanque-Delabrouille, N.; Palmese, A.; Zhiwei, P.; Pappalardo, D.; Peng, X.; Percival, W. J.; Perruchot, S.; Pogge, R.; Poppett, C.; Porredon, A.; Prada, F.; Prochaska, J.; Pucha, R.; Perez-Fernandez, A.; Perez-Rafols, I; Rabinowitz, D.; Raichoor, A.; Ramirez-Solano, S.; Ramirez-Perez, Cesar; Ravoux, C.; Reil, K.; Rezaie, M.; Rocher, A.; Rockosi, C.; Roe, N. A.; Roodman, A.; Ross, A. J.; Rossi, G.; Ruggeri, R.; Ruhlmann-Kleider, V; Sabiu, C. G.; Safonova, S.; Said, K.; Saintonge, A.; Catonga, Javier Salas; Samushia, L.; Sanchez, E.; Saulder, C.; Schaan, E.; Schlafly, E.; Schlegel, D.; Schmoll, J.; Scholte, D.; Schubnell, M.; Secroun, A.; Seo, H.; Serrano, S.; Sharples, Ray M.; Sholl, Michael J.; Silber, Joseph Harry; Silva, D. R.; Sirk, M.; Siudek, M.; Smith, A.; Sprayberry, D.; Staten, R.; Stupak, B.; Tan, T.; Tarle, Gregory; Tie, Suk Sien; Tojeiro, R.; Urena-Lopez, L. A.; Valdes, F.; Valenzuela, O.; Valluri, M.; Vargas-Magana, M.; Verde, L.; Walther, M.; Wang, B.; Wang, M. S.; Weaver, B. A.; Weaverdyck, C.; Wechsler, R.; Wilson, Michael J.; Yang, J.; Yu, Y.; Yuan, S.; Yeche, Christophe; Zhang, H.; Zhang, K.; Zhao, Cheng; Zhou, Rongpu; Zhou, Zhimin; Zou, H.; Zou, J.; Zou, S.; Zu, Y.; DESI Collaboration.--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) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z > 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3fdg2 diameter prime-focus corrector; a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface; 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs; and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0farcs1 and a median signal-to-noise ratio of 7 of the [O ii] doublet at 8 × 10−17 erg s−1 cm−2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned. © 2022. The Author(s). Published by the American Astronomical Society., This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract. Additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising–Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain, and by the DESI Member Institutions: Aix-Marseille University; Argonne National Laboratory; Barcelona-Madrid Regional Participation Group; Brookhaven National Laboratory; Boston University; Brazil Regional Participation Group; Carnegie Mellon University; CEA-IRFU, Saclay; China Participation Group; Cornell University; Durham University; École Polytechnique Fédérale de Lausanne; Eidgenössische Technische Hochschule, Zürich; Fermi National Accelerator Laboratory; Granada-Madrid-Tenerife Regional Participation Group; Harvard University; Kansas State University; Korea Astronomy and Space Science Institute; Korea Institute for Advanced Study; Lawrence Berkeley National Laboratory; Laboratoire de Physique Nucléaire et de Hautes Energies; Ludwig Maximilians University; Max Planck Institute; Mexico Regional Participation Group; New York University; NSF's National Optical-Infrared Astronomy Research Laboratory; Ohio University; Perimeter Institute; Shanghai Jiao Tong University; Siena College; SLAC National Accelerator Laboratory; Southern Methodist University; Swinburne University; The Ohio State University; Universidad de los Andes; University of Arizona; University of Barcelona; University of California, Berkeley; University of California, Irvine; University of California, Santa Cruz; University College London; University of Florida; University of Michigan at Ann Arbor; University of Pennsylvania; University of Pittsburgh; University of Portsmouth; University of Queensland; University of Rochester; University of Toronto; University of Utah; University of Waterloo; University of Wyoming; University of Zurich; UK Regional Participation Group; and Yale University. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Full list of authors: Dey, Arjun; Najita, Joan R.; Koposov, Sergey E.; Josephy-Zack, J.; Maxemin, Gabriel; Bell, Eric F.; Poppett, C.; Patel, E.; Beraldo e Silva, L.; Raichoor, A.; Schlegel, D.; Lang, D.; Meisner, A.; Myers, Adam D.; Aguilar, J.; Ahlen, S.; Allende Prieto, C.; Brooks, D.; Cooper, A. P.; Dawson, K. S.; de la Macorra, A.; Doel, P.; Font-Ribera, A.; Garcia-Bellido, Juan; Gontcho, S. Gontcho A.; Guy, J.; Honscheid, K.; Kehoe, R.; Kisner, T.; Kremin, A.; Landriau, M.; Le Guillou, L.; Levi, Michael E.; Li, T. S.; Martini, Paul; Miquel, R.; Moustakas, J.; Nie, Jundan; Palanque-Delabrouille, N.; Prada, F.; Schlafly, E. F.; Sharples, Ray M.; Tarle, Gregory; Ting, Yuan-Sen; Tyas, L.; Valluri, M.; Wechsler, Risa H.; Zou, H.--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., We present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger—a galactic immigration event—in exquisite detail. Of the 11,416 sources studied in 3.75 hr of on-sky exposure time, 7438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf, and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1–2 Gyr ago. Significant numbers of metal-rich stars ([Fe/H] > − 0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125 kpc to be ${\mathrm{log}}_{10}\,{M}_{\mathrm{NFW}}(\lt 125\,\mathrm{kpc})/{M}_{\odot }={11.80}_{-0.10}^{+0.12}$. The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies. © 2023. The Author(s). Published by the American Astronomical Society., A.D. and J.N.'s research activities are supported by the NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. A.D. and J.N.'s research is also supported in part by Fellowships from the John Simon Guggenheim Memorial Foundation and by the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics. J.N. also acknowledges support from the Harvard Radcliffe Fellowship Program of the Radcliffe Institute for Advanced Study at Harvard University. J.N., G.M., and J.J.-Z. acknowledge support from the Harvard University's Radcliffe Research Partners Program of the Radcliffe Institute for Advanced Study. E.F.B. is grateful for support from the National Science Foundation through grant NSF-AST 2007065. L.B.S. acknowledges NASA-ATP award 80NSSC20K0509 and Science Foundation AAG grant AST-2009122. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institutions. The authors are honored to be permitted to conduct scientific research on Iolkam Du'ag (Kitt Peak), a mountain with particular significance to the Tohono O'odham Nation. This work was performed in part at Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. This work was partially supported by a grant from the Simons Foundation., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).