Accelerated formation of ultra-massive galaxies in the first billion years.
basic_science · Level V
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- Record sourced from PubMed, PMID 39537883.
- Also identified by DOI 10.1038/s41586-024-08094-5.
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Abstract
Recent James Webb Space Telescope (JWST) observations have revealed an unexpected abundance of massive-galaxy candidates in the early Universe, extending further in redshift and to lower luminosity than what had previously been found by submillimetre surveys<sup>1-6</sup>. These JWST candidates have been interpreted as challenging the Λ cold dark-matter cosmology (where Λ is the cosmological constant)<sup>7-9</sup>, but, so far, these studies have mostly relied on only rest-frame ultraviolet data and have lacked spectroscopic confirmation of their redshifts<sup>10-16</sup>. Here we report a systematic study of 36 massive dust-obscured galaxies with spectroscopic redshifts between 5 and 9 from the JWST FRESCO survey. We find no tension with the Λ cold dark-matter model in our sample. However, three ultra-massive galaxies (logM<sub>★</sub>/M<sub>⊙</sub> ≳ 11.0, where M<sub>★</sub> is the stellar mass and M<sub>⊙</sub> is the mass of the Sun) require an exceptional fraction of 50 per cent of baryons converted into stars-two to three times higher than the most efficient galaxies at later epochs. The contribution from an active galactic nucleus is unlikely because of their extended emission. Ultra-massive galaxies account for as much as 17 per cent of the total cosmic star-formation-rate density<sup>17</sup> at redshifts between about five and six.