Electron Temperature Relations And The Direct N, O, Ne, S And Ar abundances Of 49959 Star-forming Galaxies In DESI Data Release 2

We present the largest direct-method abundance catalogue of galaxies to date, containing measurements of 49959 star-forming galaxies at z<0.96 from DESI Data Release 2. By directly measuring electron temperatures across multiple ionization zones, we provide constraints on a number of electron temperature relations finding good consistency with previous literature relations. Using these 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 49766 galaxies, leading to the discovery of the two most metal-poor galaxies in the nearby Universe, with oxygen abundances of 12+log(O/H)=6.77+0.03−0.03 dex (1.2% Z_⊙) and 12+log(O/H)=6.81+0.04−0.04 dex (1.3% Z_⊙). We identify a rare outlier population of 139 galaxies with high N/O ratios at low metallicity, reminiscent of galaxy abundances observed in the early Universe.

We find these high N/O galaxies are more massive than typical galaxies at the same metallicity. We find the Ne/O ratio is constant at low metallicity but increases significantly at 12+log(O/H)>8.105±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.

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

Comments: 20 pages, 12 figures. Submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2601.02463 [astro-ph.GA](or arXiv:2601.02463v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2601.02463
Focus to learn more
Submission history
From: Dirk Scholte
[v1] Mon, 5 Jan 2026 19:00:00 UTC (7,422 KB)
https://arxiv.org/abs/2601.02463
Astrobiology, Astrochemistry,