Source: FLARES can make z≈7 quenched galaxies, but too few

Turner et al., “The Nature of High-Redshift Massive Quiescent Galaxies—Searching for RUBIES-UDS-QG-z7 in FLARES” (2025 preprint; subsequently published) directly tests Weibel et al.’s spectroscopic z=7.29 system. The authors identify two lookalikes in FLARES when comparing simulated observable light and stellar histories, so an early quenched galaxy is possible within their ΛCDM simulation. However, models strongly underpredict the rate implied by the one observed object, by about two orders of magnitude.

The simulated systems grow in bursts and their black-hole activity heats or expels gas, rapidly stopping star formation. Adjusting how AGN feedback works, perhaps allowing faster-than-Eddington accretion, and modeling systematic differences may bring abundances closer. Their derived properties are sensitive to synthetic spectral-model choices; matches of a few objects and disagreement in frequency are separate claims. Follow-up ALMA detected remaining cold gas, another empirical check on complete-gas-expulsion scenarios.

Use this as the named counterpoint to both “nothing to explain” and “ΛCDM cannot produce these objects” at the open question.