Extremely Metal-Poor Galaxies in DESI DR1: Connections to Galaxies in the Early Universe

TL;DR

This study identifies and analyzes extremely metal-poor galaxies in DESI DR1, revealing their similarities to early universe galaxies in star formation and metallicity, thus providing local analogs for primordial galaxy evolution.

Contribution

It presents the largest sample of confirmed XMPGs from DESI DR1 and demonstrates their connection to high-redshift galaxy properties, highlighting their importance for studying early galaxy formation.

Findings

XMPGs follow an elevated, shallower star-forming main sequence.

XMPGs' star formation rates align with high-redshift galaxies at higher masses.

XMPGs deviate below the local metallicity relation, similar to early universe galaxies.

Abstract

Extremely Metal-Poor Galaxies (XMPGs), defined as having metallicities below 10\% of the solar value, are considered possible local analogs to primordial systems and offer a unique window into early galaxy evolution. This study presents a large-scale search for XMPGs using data from the Dark Energy Spectroscopic Instrument DR1, systematically evaluating their resemblance to high-redshift galaxies. From a parent sample of over 14 million galaxies, we identify 656 (551 new) confirmed XMPGs and 767 (670 new) high-quality candidates via the direct $T_{\mathrm{e}}$ method. Results reveal that XMPGs follow a distinct star-forming main sequence (SFMS) that is elevated and shallower than that of the comparing star-forming galaxies. Notably, at higher stellar masses ($M_{\star} > 10^{7.5} M_{\odot}$), the XMPG SFMS converges with the sequence observed in high-redshift galaxies by James Webb Space Telescope (JWST), indicating that mature XMPGs sustain star formation rates comparable to their primordial counterparts. Furthermore, XMPGs consistently deviate below the local fundamental metallicity relation, mirroring high-redshift galaxy behavior. These findings demonstrate that XMPGs not only exhibit low metallicities but also preserve scaling relations characteristic of the early Universe, confirming their potential value as local laboratories for studying early galaxy formation processes.