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Published January 2026 | Version Published
Journal Article Open

COSMOS Spectroscopic Redshift Compilation (First Data Release): 488,000 Redshifts Encompassing Two Decades of Spectroscopy

Creators

  • 1. ROR icon University of Kentucky
  • 2. ROR icon Rochester Institute of Technology
  • 3. ROR icon Max Planck Institute for Extraterrestrial Physics
  • 4. ROR icon French National Centre for Scientific Research
  • 5. ROR icon University of California, Santa Barbara
  • 6. ROR icon The University of Texas at Austin
  • 7. ROR icon University of Copenhagen
  • 8. ROR icon Institute of Astronomy and Astrophysics, Academia Sinica
  • 9. ROR icon University of Toronto
  • 10. ROR icon International Centre for Radio Astronomy Research
  • 11. ROR icon Centre of Excellence for All-Sky Astrophysics
  • 12. ROR icon Australian National University
  • 13. ROR icon University of Valparaíso
  • 14. ROR icon University of Bologna
  • 15. INAF–Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
  • 16. ROR icon Astronomical Observatory of Rome
  • 17. ROR icon Infrared Processing and Analysis Center
  • 18. ROR icon University of California, Riverside
  • 19. ROR icon University of Hawaii at Hilo
  • 20. ROR icon University of California, Berkeley
  • 21. ROR icon Lawrence Berkeley National Laboratory
  • 22. ROR icon Aalto University
  • 23. ROR icon University of Helsinki
  • 24. ROR icon TU Dresden
  • 25. ROR icon Deutsches Elektronen-Synchrotron DESY
  • 26. Deutsches Zentrum für Astrophysik, Postplatz 1, 02826 Görlitz, Germany
  • 27. ROR icon Brera Astronomical Observatory
  • 28. ROR icon Technical University of Denmark
  • 29. ROR icon National Astronomical Observatory of Japan
  • 30. ROR icon Space Telescope Science Institute
  • 31. ROR icon University of Tokyo
  • 32. ROR icon ETH Zurich
  • 33. ROR icon Purple Mountain Observatory
  • 34. ROR icon Ehime University
  • 35. ROR icon The Graduate University for Advanced Studies, SOKENDAI
  • 36. ROR icon Peking University
  • 37. ROR icon University of Hawaii at Manoa
  • 38. ROR icon California Institute of Technology
  • 39. ROR icon University of California, Davis
  • 40. ROR icon Johns Hopkins University
  • 41. ROR icon Florida State University
  • 42. ROR icon Laboratoire de Physique Nucléaire et de Hautes Énergies
  • 43. ROR icon Heidelberg University
  • 44. ROR icon Tel Aviv University
  • 45. ROR icon University of Connecticut
  • 46. ROR icon University of Cape Town
  • 47. Inter-University Institute for Data Intensive Astronomy, Department of Physics and Astronomy, University of the Western Cape, Robert Sobukwe Road, 7535 Bellville, Cape Town, South Africa
  • 48. ROR icon Istituto di Radioastronomia di Bologna
  • 49. ROR icon University of Massachusetts Amherst

Abstract

We present the COSMOS Spectroscopic Redshift Compilation encompassing ∼20 yr of spectroscopic redshifts within a 10 deg2 area centered on the 2 deg2 COSMOS legacy field. This compilation contains 487,666 redshifts of 266,284 unique objects from 138 individual programs up to z ∼ 8 with median stellar mass ∼108.4–1010 M⊙ (redshift dependent). Rest-frame NUVrJ colors and star formation rate–stellar mass correlations show that the compilation primarily contains low-to-intermediate-mass star-forming and massive, quiescent galaxies at z < 1.25 and mostly low-mass bursty star-forming galaxies at z > 2. Sources in the compilation cover a diverse range of environments, including protoclusters such as “Hyperion.” The full compilation is 50% spectroscopically complete by i ∼ 23.4 mag and Ks ∼ 21.6 mag; however, this is redshift dependent. Spatially, the compilation is >50% (>30%) complete within the central (outer) region limited to i < 24 mag and Ks < 22.5 mag, separately. We demonstrate how the compilation can be used to validate photometric redshifts and investigate calibration metrics. By training self-organizing maps on COSMOS2020/Classic and projecting the compilation onto it, we find key subpopulations currently lacking spectroscopic coverage, including z < 1 intermediate-mass quiescent and low-/intermediate-mass bursty star-forming galaxies, z ∼ 2 massive quiescent galaxies, and z > 3 massive star-forming galaxies. This highlights how combining self-organizing maps with our compilation can provide guidance for future spectroscopic observations to get a complete spectroscopic view of galaxy populations. Lastly, the compilation will undergo periodic data releases incorporating new spectroscopic redshifts and providing a lasting legacy resource for the community.

Copyright and License

© 2025. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

The authors thank the anonymous referee for their comments and suggestions that aided in enhancing the quality of this work. The authors acknowledge the hard work of all members of each respective program that have made this compilation possible. This material is based on work supported by the National Science Foundation under grant No. 2009572 and by NASA under award No. 80NSSC22K0854. The French contingent of the COSMOS team is partly supported by the Centre National d’Etudes Spatiales (CNES). O.I. acknowledges the funding of the French Agence Nationale de la Recherche for the project iMAGE (grant ANR-22-CE31-0007). This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France (F. Ochsenbein et al. 2000). This research has made use of NASA’s Astrophysics Data System.

Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 nonprofit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

Based on observations obtained at the international Gemini Observatory, a program of NSF NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the US National Science Foundation on behalf of the Gemini Observatory partnership: the US National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovacões e Comunicacões (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea).

Facilities

AAT - Anglo-Australian Telescope, HST - Hubble Space Telescope satellite (ACS, WFC3-IR) - , ALMA - Atacama Large Millimeter Array, LMT - , SMA - SubMillimeter Array, NOEMA - , ING:Herschel - Isaac Newton Group's William Herschel Telescope (LIRIS), TNG - Telescopio Nazionale Galileo (NICS), Keck:I - KECK I Telescope (LRIS, MOSFIRE) - , Keck:II - KECK II Telescope (DEIMOS, NIRSPEC) - , LBT - Large Binocular Telescope Observatory (LUCI1, LUCI2) - , VLT:Antu - Very Large Telescope (Antu) (FORS1, FORS2, KMOS) - , VLT:Kueyen - Very Large Telescope (Kueyen) (X-SHOOTER), VLT:Melipal - Very Large Telescope (Melipal) (VIMOS), VLT:Yepun - Very Large Telescope (Yepun) (MUSE, SINFONI) - , MMT - MMT at Fred Lawrence Whipple Observatory (Binospec, Hectospec) - , Mayall - Kitt Peak National Observatory's 4 meter Mayall Telescope (DESI), Subaru - Subaru Telescope (FMOS, FOCAS, MOIRCS) - , Gemini:South - Gemini South Telescope (GMOS), HET - McDonald Observatory's Hobby-Eberly Telescope (VIRUS), Magellan:Baade - Magellan I Walter Baade Telescope (IMACS, FIRE) - , Magellan:Clay - Magellan II Landon Clay Telescope (LDSS3, M2FS) - , Spitzer - Spitzer Space Telescope satellite, Gaia - , Sloan - Sloan Digital Sky Survey Telescope, Du Pont - Du Pont Telescope

Software References

astropy (Astropy Collaboration et al. 2013, 2018, 2022), CIGALE (M. Boquien et al. 2019), LePHARE (S. Arnouts et al. 1999; O. Ilbert et al. 2006), numpy (C. R. Harris et al. 2020), sompy (V. Moosavi et al. 2014).

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Additional details

Additional titles

Alternative title
COSMOS Spectroscopic Redshift Compilation (First Data Release): 165k Redshifts Encompassing Two Decades of Spectroscopy

Related works

Is new version of
Discussion Paper: arXiv:2503.00120 (arXiv)

Funding

National Science Foundation
2009572
National Aeronautics and Space Administration
80NSSC22K0854
Centre National d'Études Spatiales
Agence Nationale de la Recherche
ANR-22-CE31-0007
W. M. Keck Foundation

Dates

Submitted
2025-02-28
Accepted
2025-10-21
Available
2025-12-18
Published

Caltech Custom Metadata

Caltech groups
Astronomy Department , Infrared Processing and Analysis Center (IPAC) , Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published