Nearly pristine gas in a galaxy 1 billion years after the Big Bang
Abstract
Excitation of carbon and oxygen ions is the primary mechanism by which collapsing gas clouds dissipate heat to form new stars. At early cosmic times, in galaxies with chemically pristine gas, many stars are expected to have masses far larger than the mass of our sun due to the deficit in these elements. We searched for ultra-metal-poor galaxies using their spectroscopic absorption signatures in front of bright background quasars, employing the new GHOST high-resolution spectrograph. Here we report the discovery of the first galaxy containing a reservoir of neutral hydrogen gas with metallicity below the ultra-metal-poor threshold: with a measured carbon-to-hydrogen ratio 11,000 times lower than the Sun, it is the most pristine ever found by a factor of four. UMP-DLA-1 is the only known galaxy with measured carbon and oxygen abundances too low to enable efficient formation of stars with solar mass or below. The low metallicity alone therefore guarantees a top-heavy stellar population, providing a direct view of the chemical composition imprinted by massive low-metallicity stars that perished long before the present day: an elevated oxygen-to-carbon ratio. The abundance pattern of UMP-DLA-1 is likely a close representation of the atomic yields of first- or early second-generation stars.
Related
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- Massive black holes in the first billion years with JWST
- Evidence of a massive accretion event 1.8 billion years before the Gaia-Sausage-Enceladus merger
- Precise C-N-O Abundances of Individual Galaxies in the First Billion Years from Ultra-Deep, Rest-UV-to-Optical JWST Spectroscopy
- Galaxies in the first two billion years: Earlier formation and quenching with surface-density modulated star formation and feedback
BibTeX
@misc{bosman2026nearly,
title = {{Nearly pristine gas in a galaxy 1 billion years after the Big Bang}},
author = {Sarah E. I. Bosman and Frederick B. Davies and Louise Welsh and Emanuele P. Farina and Prakash Gaikwad and Benedetta Spina and Barun Maity and Ryan Cooke and Klaudia Protušová and Valentina D'Odorico and Eduardo Bañados and James S. Bolton and Rebecca L. Davies and Xiaohui Fan and Martin G. Haehnelt and Joseph F. Hennawi and Tahlia J. Hill and Seyeon Hwang and Vid Iršič and Laura Keating and Girish Kulkarni and Samuel Lai and Emma V. Ryan-Weber and Lasse Seyberlich and Molly Wolfson},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.16509},
eprint = {2610.16509},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.16509},
}
RIS
TY - UNPB
TI - Nearly pristine gas in a galaxy 1 billion years after the Big Bang
AU - Sarah E. I. Bosman
AU - Frederick B. Davies
AU - Louise Welsh
AU - Emanuele P. Farina
AU - Prakash Gaikwad
AU - Benedetta Spina
AU - Barun Maity
AU - Ryan Cooke
AU - Klaudia Protušová
AU - Valentina D'Odorico
AU - Eduardo Bañados
AU - James S. Bolton
AU - Rebecca L. Davies
AU - Xiaohui Fan
AU - Martin G. Haehnelt
AU - Joseph F. Hennawi
AU - Tahlia J. Hill
AU - Seyeon Hwang
AU - Vid Iršič
AU - Laura Keating
AU - Girish Kulkarni
AU - Samuel Lai
AU - Emma V. Ryan-Weber
AU - Lasse Seyberlich
AU - Molly Wolfson
PY - 2026
DA - 2026/10/12
PB - arXiv
DO - 10.48550/arxiv.2610.16509
UR - https://arxiv.org/abs/2610.16509
AB - Excitation of carbon and oxygen ions is the primary mechanism by which collapsing gas clouds dissipate heat to form new stars. At early cosmic times, in galaxies with chemically pristine gas, many stars are expected to have masses far larger than the mass of our sun due to the deficit in these elements. We searched for ultra-metal-poor galaxies using their spectroscopic absorption signatures in front of bright background quasars, employing the new GHOST high-resolution spectrograph. Here we report the discovery of the first galaxy containing a reservoir of neutral hydrogen gas with metallicity below the ultra-metal-poor threshold: with a measured carbon-to-hydrogen ratio 11,000 times lower than the Sun, it is the most pristine ever found by a factor of four. UMP-DLA-1 is the only known galaxy with measured carbon and oxygen abundances too low to enable efficient formation of stars with solar mass or below. The low metallicity alone therefore guarantees a top-heavy stellar population, providing a direct view of the chemical composition imprinted by massive low-metallicity stars that perished long before the present day: an elevated oxygen-to-carbon ratio. The abundance pattern of UMP-DLA-1 is likely a close representation of the atomic yields of first- or early second-generation stars.
ER -