{ "abstract": "We present details regarding a composite spectrum of quasar (QSO) absorption line systems. In this composite spectrum, we identify more than 70 absorption lines and observe oxygen and hydrogen emission features at a higher signal-to-noise ratio than any previous study. As the light from a distant quasar travels towards an observer, it may interact with the circumgalactic medium of an intervening galaxy, forming absorption lines. In order to maximize the signal of these absorption lines, we have selected a sample of 239,174 quasar spectra from the second data release of the Dark Energy Spectroscopic Instrument (DESI), each identified to have absorption lines resulting from such an interaction. By stacking these spectra in the rest frame of the absorption and calculating a median composite spectrum, we are able to isolate and enhance these absorption lines. We provide a full atlas of all detected absorption and emission lines as well as their fit centroids and equivalent width values. We additionally provide analysis of composites constructed using subsamples of absorbers in both redshift and Mg ii equivalent width bins. We find that there is minimal redshift evolution across the considered absorber samples. Additionally, we find that dense gas signatures, such as the presence of Na I absorption, are strongest in the highest equivalent width absorber sample, and that the strengths of the Si IV and C IV absorption lines show a relatively weak correlation with Mg II equivalent width. This atlas should aid in future studies investigating the compositions and physical conditions of these absorbers.", "abstract_shown": true, "affiliations": [ "University of Wyoming", "NSF NOIRLab", "Lawrence Berkeley National Laboratory", "Institut d’Astrophysique de Paris", "Université Paris-Saclay", "Boston University", "University of Rochester", "Università degli Studi di Milano", "INAF-Osservatorio Astronomico di Brera", "University College London", "Universidad Nacional Autónoma de México", "University of Toronto", "University of Pittsburgh", "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", "University of Virginia", "Fermi National Accelerator Laboratory", "Sorbonne Université", "Universitat Autònoma de Barcelona", "Institució Catalana de Recerca i Estudis Avançats", "Department of Physics and Astronomy", "University of Waterloo", "Perimeter Institute for Theoretical Physics", "Instituto de Astrofísica de Andalucía (CSIC)", "Universitat Politècnica de Catalunya", "Sejong University", "CIEMAT", "University of Michigan", "Chinese Academy of Sciences" ], "article_type": null, "arxiv": null, "author_total": 46, "authors": [ { "affs": [ 0, 1 ], "name": "Lucas Napolitano", "orcid": "0000-0002-5166-8671" }, { "affs": [ 0 ], "name": "Adam D. Myers" }, { "affs": [ 0 ], "name": "Adam Tedeschi" }, { "affs": [ 2 ], "name": "Abhijeet Anand", "orcid": "0000-0003-2923-1585" }, { "affs": [ 3, 4 ], "name": "Hiram K. Herrera-Alcantar", "orcid": "0000-0002-9136-9609" }, { "affs": [ 2 ], "name": "Jessica Aguilar", "orcid": "0000-0003-0822-452X" }, { "affs": [ 5 ], "name": "Steven Ahlen", "orcid": "0000-0001-6098-7247" }, { "affs": [ 2 ], "name": "Stephen Bailey", "orcid": "0000-0003-4162-6619" }, { "affs": [ 6 ], "name": "Segev BenZvi", "orcid": "0000-0001-5537-4710" }, { "affs": [ 7, 8 ], "name": "Davide Bianchi", "orcid": "0000-0001-9712-0006" }, { "affs": [ 9 ], "name": "David Brooks", "orcid": "0000-0002-8458-5047" }, { "affs": [ 2 ], "name": "Todd Claybaugh" }, { "affs": [ 2 ], "name": "Andrei Cuceu", "orcid": "0000-0002-2169-0595" }, { "affs": [ 10 ], "name": "Axel de la Macorra", "orcid": "0000-0002-1769-1640" }, { "affs": [ 1 ], "name": "Arjun Dey", "orcid": "0000-0002-4928-4003" }, { "affs": [ 11, 12 ], "name": "Biprateep Dey", "orcid": "0000-0002-5665-7912" }, { "affs": [ 9 ], "name": "Peter Doel", "orcid": "0000-0002-6397-4457" }, { "affs": [ 13 ], "name": "Andreu Font-Ribera", "orcid": "0000-0002-3033-7312" }, { "affs": [ 14 ], "name": "Jaime E. Forero-Romero", "orcid": "0000-0002-2890-3725" }, { "affs": [ 15, 16, 17 ], "name": "Enrique Gaztañaga", "orcid": "0000-0001-9632-0815" }, { "affs": [ 2, 18 ], "name": "Satya Gontcho A Gontcho", "orcid": "0000-0003-3142-233X" }, { "affs": [ 19 ], "name": "Gaston Gutierrez", "orcid": "0000-0003-0825-0517" }, { "affs": [ 2 ], "name": "Julien Guy", "orcid": "0000-0001-9822-6793" }, { "affs": [ 1 ], "name": "Dick Joyce", "orcid": "0000-0003-0201-5241" }, { "affs": [ 2 ], "name": "Anthony Kremin", "orcid": "0000-0001-6356-7424" }, { "affs": [ 2 ], "name": "Martin Landriau", "orcid": "0000-0003-1838-8528" }, { "affs": [ 20 ], "name": "Laurent Le Guillou", "orcid": "0000-0001-7178-8868" }, { "affs": [ 21 ], "name": "Marc Manera", "orcid": "0000-0003-4962-8934" }, { "affs": [ 1 ], "name": "Aaron Meisner", "orcid": "0000-0002-1125-7384" }, { "affs": [ 13, 22 ], "name": "Ramon Miquel", "orcid": "0000-0002-6610-4836" }, { "affs": [ 23 ], "name": "John Moustakas", "orcid": "0000-0002-2733-4559" }, { "affs": [ 16 ], "name": "Seshadri Nadathur", "orcid": "0000-0001-9070-3102" }, { "affs": [ 2, 4 ], "name": "Nathalie Palanque-Delabrouille", "orcid": "0000-0003-3188-784X" }, { "affs": [ 24, 25 ], "name": "Will Percival", "orcid": "0000-0002-0644-5727" }, { "affs": [ 26 ], "name": "Francisco Prada", "orcid": "0000-0001-7145-8674" }, { "affs": [ 27 ], "name": "Ignasi Pérez-Ràfols", "orcid": "0000-0001-6979-0125" }, { "affs": [ 28 ], "name": "Graziano Rossi" }, { "affs": [ 29 ], "name": "Eusebio Sanchez", "orcid": "0000-0002-9646-8198" }, { "affs": [ 2 ], "name": "David Schlegel", "orcid": "0000-0002-5042-5088" }, { "affs": [ 30 ], "name": "Michael Schubnell" }, { "affs": [ 2 ], "name": "Joesph Harry Silber", "orcid": "0000-0002-3461-0320" }, { "affs": [ 1 ], "name": "David Sprayberry", "orcid": "0000-0001-7583-6441" }, { "affs": [ 30 ], "name": "Gregory Tarlé", "orcid": "0000-0003-1704-0781" }, { "affs": [ 1 ], "name": "Benjamin Alan Weaver" }, { "affs": [ 2 ], "name": "Rongpu Zhou", "orcid": "0000-0001-5381-4372" }, { "affs": [ 31 ], "name": "Hu Zou", "orcid": "0000-0002-6684-3997" } ], "bibtex": "https://research.draconitic.com/paper/6v5s1b5r1t3kn.bib", "cited_by": 0, "doi": "10.3847/1538-3881/aea6da", "fulltext_url": null, "id": "6v5s1b5r1t3kn", "issns": [ "0004-6256", "1538-3881" ], "landing_url": "https://iopscience.iop.org/article/10.3847/1538-3881/aea6da", "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|Galaxies: Formation, Evolution, Phenomena" ] ], "openalex": "W4417011563", "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-3881/aea6da/pdf", "pmcid": null, "pmid": null, "published": "2026-10-07", "publisher": "American Astronomical Society", "ris": "https://research.draconitic.com/paper/6v5s1b5r1t3kn.ris", "sources": [ { "first_seen": "2026-10-30T12:18:14Z", "native_id": "10.3847/1538-3881/aea6da", "source": "crossref", "url": "https://iopscience.iop.org/article/10.3847/1538-3881/aea6da" } ], "subjects": [ { "field": "astronomy", "origin": "openalex:3103|Galaxies: Formation, Evolution, Phenomena", "subfield": "galaxies" } ], "title": "The Composite Spectrum of QSO Absorption Line Systems in DESI DR2", "title_text": "The Composite Spectrum of QSO Absorption Line Systems in DESI DR2", "type": "peer-reviewed", "updated_at": "2026-10-30T12:18:14Z", "url": "https://research.draconitic.com/paper/6v5s1b5r1t3kn", "venue": "The Astronomical Journal", "versions": [] }