A large sample of extremely metal-poor galaxies at z < 1 identified from the DESI early data

Hu Zou*, Jipeng Sui, Amélie Saintonge, Dirk Scholte, John Moustakas, Malgorzata Siudek, Arjun Dey, Stephanie Juneau, Weijian Guo, Rebecca Canning, J. Aguilar, S. Ahlen, D. Brooks, T. Claybaugh, K. Dawson, A. de la Macorra, P. Doel, J. E. Forero-Romero, S. Gontcho A Gontcho, K. HonscheidM. Landriau, L. Le Guillou, M. Manera, A. Meisner, R. Miquel, Jundan Nie, C. Poppett, M. Rezaie, G. Rossi, E. Sanchez, M. Schubnell, H. Seo, G. Tarlé, Zhimin Zhou, Siwei Zou

*Corresponding author for this work

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Extremely metal-poor galaxies (XMPGs) at relatively low redshift are excellent laboratories for studying galaxy formation and evolution in the early universe. Much effort has been spent on identifying them from large-scale spectroscopic surveys or spectroscopic follow-up observations. Previous work has identified a few hundred XMPGs. In this work, we obtain a large sample of 223 XMPGs at z < 1 from the early data of the Dark Energy Spectroscopic Instrument (DESI). The oxygen abundance is determined using the direct T e method based on the detection of the [O iii]λ4363 line. The sample includes 95 confirmed XMPGs based on the oxygen abundance uncertainty; the remaining 128 galaxies are regarded as XMPG candidates. These XMPGs are only 0.01% of the total DESI observed galaxies. Their coordinates and other properties are provided in the paper. The most XMPGs have an oxygen abundance of ∼1/34 Z , a stellar mass of about 1.5 × 107 M ⊙, and a star formation rate of 0.22 M yr−1. The two most XMPGs present distinct morphologies suggesting different formation mechanisms. The local environmental investigation shows that XMPGs preferentially reside in relatively low-density regions. Many of them fall below the stellar mass-metallicity relations (MZRs) of normal star-forming galaxies. From a comparison of the MZR with theoretical simulations, it appears that XMPGs are good analogs to high-redshift star-forming galaxies. The nature of these XMPG populations will be further investigated in detail with larger and more complete samples from the ongoing DESI survey.

Original languageEnglish
Article number173
Number of pages18
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 24 Jan 2024


  • UKRI
  • STFC

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