{ "abstract": "We present the catalog of RR Lyrae stars (RRLs) observed in the first year of operations of the Dark Energy Spectroscopic Instrument (DESI) survey. This catalog contains 6240 RRLs out to ∼120 kpc from the Galactic center and over 12,000 individual epochs with homogeneously derived stellar atmospheric parameters. We introduce a novel methodology to model the cyclical variation of the spectroscopic properties of RRLs from single-epoch measurements. We employ this method to infer the systemic velocities and mean temperatures of fundamental- and first-overtone-mode RRLs in our sample (without distinguishing between individual spectral lines). For fundamental-mode pulsators, we obtain radial velocity curves with amplitudes of ∼30–80 km s ⁻¹ and effective temperature curves with 300–1000 K variations, whereas for first-overtone pulsators these amplitudes are ∼20 km s ⁻¹ and ∼600 K, respectively. We use our sample to study the metallicity distribution of the halo and its dependence on Galactocentric distance ( R GC ). Using a radius-dependent mixture model, we split the data into chemodynamically distinct components and find that our inner halo sample ( R GC ≲ 50 kpc) is predominantly composed of stars with [Fe/H] ∼ −1.5 and largely radial orbits (with an anisotropy parameter β ∼ 0.94), which we associate with the Gaia–Sausage–Enceladus merger. Stars in the halo field exhibit a broader and more metal-poor [Fe/H] distribution with more circular orbits ( β ∼ 0.39). The metallicity gradient of the metal-rich and metal-poor components is found to be 0.005 and 0.010 dex kpc ⁻¹ , respectively. Our catalog highlights DESI’s tantalizing potential for studying the Milky Way and the pulsation properties of RRLs in the era of large spectroscopic surveys.", "abstract_shown": true, "affiliations": [ "University of Toronto", "University of Edinburgh", "University of Cambridge", "Durham University", "University of Arizona", "Observatório Nacional", "University of Michigan", "Shanghai Jiao Tong University", "Shanghai Key Laboratory for Particle Physics and Cosmology", "National Tsing Hua University", "NSF NOIRLab", "Lawrence Berkeley National Laboratory", "Boston University", "Università degli Studi di Milano", "INAF-Osservatorio Astronomico di Brera", "University College London", "Universidad Nacional Autónoma de México", "Institut de Física d’Altes Energies (IFAE)", "Universidad de los Andes", "Institut d’Estudis Espacials de Catalunya (IEEC)", "University of Portsmouth", "Institute of Space Sciences", "Fermi National Accelerator Laboratory", "The Ohio State University", "The University of Texas at Dallas", "Sorbonne Université", "Institució Catalana de Recerca i Estudis Avançats", "University of Wyoming", "University of California", "Instituto de Astrofísica de Andalucía (CSIC)", "Universitat Politècnica de Catalunya", "Sejong University", "CIEMAT", "Ohio University", "Stanford University", "SLAC National Accelerator Laboratory", "Chinese Academy of Sciences" ], "article_type": null, "arxiv": null, "author_total": 47, "authors": [ { "affs": [ 0 ], "name": "G. E. Medina", "orcid": "0000-0003-0105-9576" }, { "affs": [ 0 ], "name": "T. S. Li", "orcid": "0000-0002-9110-6163" }, { "affs": [ 1, 2 ], "name": "S. E. Koposov", "orcid": "0000-0003-2644-135X" }, { "affs": [ 3 ], "name": "A. H. Riley", "orcid": "0000-0001-5805-5766" }, { "affs": [ 4, 5 ], "name": "L. Beraldo e Silva", "orcid": "0000-0002-0740-1507" }, { "affs": [ 6 ], "name": "M. Valluri", "orcid": "0000-0002-6257-2341" }, { "affs": [ 7, 8 ], "name": "W. Wang", "orcid": "0000-0002-5762-7571" }, { "affs": [ 1 ], "name": "A. Byström", "orcid": "0000-0002-5689-8791" }, { "affs": [ 6 ], "name": "O. Y. Gnedin", "orcid": "0000-0001-9852-9954" }, { "affs": [ 0 ], "name": "R. G. Carlberg", "orcid": "0000-0002-7667-0081" }, { "affs": [ 9 ], "name": "N. Kizhuprakkat", "orcid": "0000-0003-0853-8887" }, { "affs": [ 10 ], "name": "B. A. Weaver" }, { "affs": [ 11 ], "name": "J. Aguilar", "orcid": "0000-0003-0822-452X" }, { "affs": [ 12 ], "name": "S. Ahlen", "orcid": "0000-0001-6098-7247" }, { "affs": [ 13, 14 ], "name": "D. Bianchi", "orcid": "0000-0001-9712-0006" }, { "affs": [ 15 ], "name": "D. Brooks", "orcid": "0000-0002-8458-5047" }, { "affs": [ 11 ], "name": "T. Claybaugh" }, { "affs": [ 9 ], "name": "A. P. Cooper", "orcid": "0000-0001-8274-158X" }, { "affs": [ 16 ], "name": "A. de la Macorra", "orcid": "0000-0002-1769-1640" }, { "affs": [ 10 ], "name": "A. Dey", "orcid": "0000-0002-4928-4003" }, { "affs": [ 15 ], "name": "P. Doel", "orcid": "0000-0002-6397-4457" }, { "affs": [ 17 ], "name": "A. Font-Ribera", "orcid": "0000-0002-3033-7312" }, { "affs": [ 18 ], "name": "J. E. Forero-Romero", "orcid": "0000-0002-2890-3725" }, { "affs": [ 19, 20, 21 ], "name": "E. Gaztañaga" }, { "affs": [ 11 ], "name": "S. Gontcho A Gontcho", "orcid": "0000-0003-3142-233X" }, { "affs": [ 22 ], "name": "G. Gutierrez", "orcid": "0000-0003-0825-0517" }, { "affs": [ 11 ], "name": "J. Guy", "orcid": "0000-0001-9822-6793" }, { "affs": [ 23 ], "name": "K. Honscheid", "orcid": "0000-0002-6550-2023" }, { "affs": [ 24 ], "name": "M. Ishak", "orcid": "0000-0002-6024-466X" }, { "affs": [ 11 ], "name": "T. Kisner", "orcid": "0000-0003-3510-7134" }, { "affs": [ 11 ], "name": "M. Landriau", "orcid": "0000-0003-1838-8528" }, { "affs": [ 25 ], "name": "L. Le Guillou", "orcid": "0000-0001-7178-8868" }, { "affs": [ 10 ], "name": "A. Meisner", "orcid": "0000-0002-1125-7384" }, { "affs": [ 17, 26 ], "name": "R. Miquel", "orcid": "0000-0002-6610-4836" }, { "affs": [ 27 ], "name": "A. D. Myers" }, { "affs": [ 20 ], "name": "S. Nadathur", "orcid": "0000-0001-9070-3102" }, { "affs": [ 11, 28 ], "name": "C. Poppett", "orcid": "0000-0003-0512-5489" }, { "affs": [ 29 ], "name": "F. Prada", "orcid": "0000-0001-7145-8674" }, { "affs": [ 30 ], "name": "I. Pérez-Ràfols", "orcid": "0000-0001-6979-0125" }, { "affs": [ 31 ], "name": "G. Rossi" }, { "affs": [ 32 ], "name": "E. Sanchez", "orcid": "0000-0002-9646-8198" }, { "affs": [ 33 ], "name": "H. Seo", "orcid": "0000-0002-6588-3508" }, { "affs": [ 10 ], "name": "D. Sprayberry", "orcid": "0000-0001-7583-6441" }, { "affs": [ 6 ], "name": "G. Tarlé", "orcid": "0000-0003-1704-0781" }, { "affs": [ 34, 35 ], "name": "R. H. Wechsler", "orcid": "0000-0003-2229-011X" }, { "affs": [ 11 ], "name": "R. Zhou", "orcid": "0000-0001-5381-4372" }, { "affs": [ 36 ], "name": "H. Zou", "orcid": "0000-0002-6684-3997" } ], "bibtex": "https://research.draconitic.com/paper/59fd9nn8fdr74.bib", "cited_by": 1, "doi": "10.3847/1538-4357/ae9746", "fulltext_url": null, "id": "59fd9nn8fdr74", "issns": [ "0004-637X", "1538-4357" ], "landing_url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae9746", "language": null, "licence": "CC-BY-4.0", "licence_label": "CC BY 4.0", "licence_source": "article", "licence_url": "https://creativecommons.org/licenses/by/4.0/", "metadata_licence": null, "native_subjects": [ [ "openalex", "3103|Stellar, planetary, and galactic studies" ] ], "openalex": "W4414487608", "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae9746/pdf", "pmcid": null, "pmid": null, "published": "2026-10-01", "publisher": "American Astronomical Society", "ris": "https://research.draconitic.com/paper/59fd9nn8fdr74.ris", "sources": [ { "first_seen": "2026-10-30T12:18:11Z", "native_id": "10.3847/1538-4357/ae9746", "source": "crossref", "url": "https://iopscience.iop.org/article/10.3847/1538-4357/ae9746" } ], "subjects": [ { "field": "astronomy", "origin": "openalex:3103|Stellar, planetary, and galactic studies", "subfield": "stellar" } ], "title": "The DESI Y1 RR Lyrae Catalog. I. Empirical Modeling of the Cyclic Variation of Spectroscopic Properties and a Chemodynamical Analysis of the Outer Halo", "title_text": "The DESI Y1 RR Lyrae Catalog. I. Empirical Modeling of the Cyclic Variation of Spectroscopic Properties and a Chemodynamical Analysis of the Outer Halo", "type": "peer-reviewed", "updated_at": "2026-10-30T12:18:11Z", "url": "https://research.draconitic.com/paper/59fd9nn8fdr74", "venue": "The Astrophysical Journal", "versions": [] }