Molecular hydrogen in the extremely metal- and dust-poor galaxy Leo P
O. Grace Telford (),
Karin M. Sandstrom,
Kristen B. W. McQuinn,
Simon C. O. Glover,
Elizabeth J. Tarantino,
Alberto D. Bolatto and
Ryan J. Rickards Vaught
Additional contact information
O. Grace Telford: Princeton University
Karin M. Sandstrom: University of California, San Diego
Kristen B. W. McQuinn: Rutgers University
Simon C. O. Glover: Universität Heidelberg
Elizabeth J. Tarantino: Space Telescope Science Institute
Alberto D. Bolatto: University of Maryland
Ryan J. Rickards Vaught: University of California, San Diego
Nature, 2025, vol. 642, issue 8069, 900-904
Abstract:
Abstract The James Webb Space Telescope (JWST) has revealed unexpectedly rapid galaxy assembly in the early Universe, in tension with galaxy-formation models1–3. At the low abundances of heavy elements (metals) and dust typical in early galaxies, the formation of molecular hydrogen and its connection to star formation remain poorly understood. Some models predict that stars form in predominantly atomic gas at low metallicity4,5, in contrast to molecular gas at higher metallicities6. Despite repeated searches7, cold molecular gas has not yet been observed in any galaxy below 7% solar metallicity8. Here we report the detection of rotational emission from molecular hydrogen near the only O-type star in the 3% solar metallicity galaxy Leo P (refs. 9,10) with JWST’s Mid-Infrared Instrument/Medium Resolution Spectroscopy (MIRI-MRS) observing mode. These observations place a lower limit on Leo P’s molecular gas content, and modelling of the photodissociation region illuminated by the O star suggests a compact (≤2.6 pc radius), approximately 104 M⊙ cloud. We also report a stringent upper limit on carbon monoxide (CO) emission from a deep search with the Atacama Large Millimeter/submillimeter Array (ALMA). Our results highlight the power of MIRI-MRS to characterize even small ultraviolet-illuminated molecular clouds in the low-metallicity regime, in which the traditional observational tracer CO is uninformative. This discovery pushes the limiting metallicity at which molecular gas is present in detectable quantities more than a factor of two lower, providing crucial empirical guidance for models of the interstellar medium in early galaxies.
Date: 2025
References: Add references at CitEc
Citations:
Downloads: (external link)
https://www.nature.com/articles/s41586-025-09115-7 Abstract (text/html)
Access to the full text of the articles in this series is restricted.
Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.
Export reference: BibTeX
RIS (EndNote, ProCite, RefMan)
HTML/Text
Persistent link: https://EconPapers.repec.org/RePEc:nat:nature:v:642:y:2025:i:8069:d:10.1038_s41586-025-09115-7
Ordering information: This journal article can be ordered from
https://www.nature.com/
DOI: 10.1038/s41586-025-09115-7
Access Statistics for this article
Nature is currently edited by Magdalena Skipper
More articles in Nature from Nature
Bibliographic data for series maintained by Sonal Shukla () and Springer Nature Abstracting and Indexing ().