Electron temperature relations and the direct N, O, Ne, S and Ar abundances of 49 959 star-forming galaxies in DESI Data Release 2

Abstract We present the largest direct-method abundance catalogue of galaxies to date, containing measurements of 49 959 star-forming galaxies at z < 0.96 from DESI Data Release 2. By directly measuring electron temperatures across multiple ionisation zones, we provide constraints on a number of electron temperature relations. Using the temperature measurements, we derive reliable abundances for N, O, Ne, S and Ar and measure the evolution of abundances and abundance ratios of as a function of metallicity and other galaxy properties. Our measurements include direct oxygen abundances for 49 507 galaxies, leading to the discovery of the two most metal-poor galaxies in the nearby Universe, with oxygen abundances of $\rm 12+\log (O/H) = 6.77_{-0.03}^{+0.03} \rm dex$ (1.2% $\rm Z_{\odot }$) and $\rm 12+\log (O/H) = 6.81_{-0.04}^{+0.04} \rm dex$ (1.3% $\rm Z_{\odot }$). We identify a rare outlier population of 24 galaxies with high N/O ratios at low metallicity, reminiscent of galaxy abundances observed in the early Universe. We find the Ne/O ratio is constant at low metallicity but increases gradually at $\rm 12+log(O/H) > 8.105\pm 0.004$ dex. We show that the S/O and Ar/O abundance ratios are strongly correlated, consistent with the expected additional Type Ia enrichment channel for S and Ar. In this work we present an initial survey of the key properties of the sample, with this dataset serving as a foundation for extensive future work on galaxy abundances at low redshift.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-07-22
DOI
https://doi.org/10.1093/mnras/stag1381
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
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article

Electron temperature relations and the direct N, O, Ne, S and Ar abundances of 49 959 star-forming galaxies in DESI Data Release 2

Ting-Yun Cheng, Will J. Percival, T M Stanton, Francisco Javier Castander et al.
Monthly Notices of the Royal Astronomical Society
Galaxies: Formation, Evolution, Phenomena
article

Electron temperature relations and the direct N, O, Ne, S and Ar abundances of 49 959 star-forming galaxies in DESI Data Release 2

Ting-Yun Cheng, Will J. Percival, T M Stanton, Francisco Javier Castander, D. Scholte, A. Saintonge, J. E. Forero-Romero, E Sanchez, M Landriau, E Gaztañaga, A Meisner, A de la Macorra, A Kremin, J Aguilar, K Douglass, J Silber, B Andrews, S Gontcho A Gontcho, J Moustakas, C Poppett, R Joyce, G Gutierrez, D Schlegel, L Le Guillou, D Sprayberry, H Zou, S Ferraro, F Cullen, K Z Arellano-Cordova, G Tarlé, O Lahav, T Claybaugh, D Bianchi, B A Weaver, F Prada, G Rossi, P Martini, J Sui, P Doel, R Miquel, Z Shao, B Dey, D Brooks, I Pérez-Ràfols, S Ahlen
article en

Abstract

Abstract We present the largest direct-method abundance catalogue of galaxies to date, containing measurements of 49 959 star-forming galaxies at z < 0.96 from DESI Data Release 2. By directly measuring electron temperatures across multiple ionisation zones, we provide constraints on a number of electron temperature relations. Using the temperature measurements, we derive reliable abundances for N, O, Ne, S and Ar and measure the evolution of abundances and abundance ratios of as a function of metallicity and other galaxy properties. Our measurements include direct oxygen abundances for 49 507 galaxies, leading to the discovery of the two most metal-poor galaxies in the nearby Universe, with oxygen abundances of $\rm 12+\log (O/H) = 6.77_{-0.03}^{+0.03} \rm dex$ (1.2% $\rm Z_{\odot }$) and $\rm 12+\log (O/H) = 6.81_{-0.04}^{+0.04} \rm dex$ (1.3% $\rm Z_{\odot }$). We identify a rare outlier population of 24 galaxies with high N/O ratios at low metallicity, reminiscent of galaxy abundances observed in the early Universe. We find the Ne/O ratio is constant at low metallicity but increases gradually at $\rm 12+log(O/H) > 8.105\pm 0.004$ dex. We show that the S/O and Ar/O abundance ratios are strongly correlated, consistent with the expected additional Type Ia enrichment channel for S and Ar. In this work we present an initial survey of the key properties of the sample, with this dataset serving as a foundation for extensive future work on galaxy abundances at low redshift.

Monthly Notices of the Royal Astronomical Society
Boston University (US), Institució Catalana de Recerca i Estudis Avançats (ES), Universidad Complutense de Madrid (ES), Centre National de la Recherche Scientifique (FR), Fermi National Accelerator Laboratory (US), Institute of Space Sciences (ES), Lawrence Berkeley National Laboratory (US), University of Waterloo (CA), State Street (United States) (US), Universidad de Los Andes (CO), University of Groningen (NL), University of Pittsburgh (US), Perimeter Institute (CA), Institute for High Energy Physics (ES), University of Milan (IT), Chinese Academy of Sciences (CN), University of Michigan (US), Shanghai Astronomical Observatory (CN), Brera Astronomical Observatory (IT), Sejong University (KR), Sorbonne Université (FR), Institut d'Estudis Espacials de Catalunya (ES), Laboratoire de Physique Nucléaire et de Hautes Énergies (FR), Royal Observatory (GB), Canadian Institute for Theoretical Astrophysics (CA), Institut National de Physique Nucléaire et de Physique des Particules (FR), Community Science and Data Center (US), Istituto Nazionale di Fisica Nucleare, Sezione di Milano (IT), NSF NOIRLab (US), Universidad de Los Andes (BO), Max Planck Institute for Radio Astronomy (DE), Instituto de Astrofísica de Andalucía (ES), National Astronomical Observatories (CN), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (ES), University College London (GB), University of Virginia (US), The Ohio State University (US), University of Rochester (US), University of Portsmouth (GB), Universidad Nacional Autónoma de México (MX), Siena College (US), University of California, Berkeley (US), Universitat Politècnica de Catalunya (ES), University of Edinburgh (GB)
Openalex Percentile: Top 9%
Galaxies: Formation, Evolution, Phenomena
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