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arXiv · 2503.00155

Late-time growth weakly affects the significance of high-redshift massive galaxies

Qianran Xia·Dragan Huterer·Nhat-Minh Nguyen
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Abstract

Recent observations by the James Webb Space Telescope have revealed massive galaxies at very high redshift ($z\simeq 7-15$). The question of whether the existence of such galaxies is expected in the corresponding JWST surveys has received a lot of attention, though the answer straddles areas of cosmology and complex astrophysical details of high-redshift galaxy formation. The growth rate of density fluctuations determines the amplitude of overdensities that collapse to form galaxies. Late-time modifications of growth, combined with measurements at both $z\sim 1$ from large-scale structure and $z\sim 1000$ from the cosmic microwave background, affect the predictions for the abundance of first galaxies in the universe. In this paper, we point out that the late-time growth rate of structure affects the statistical significance of high-redshift, high-mass objects very weakly. Consequently, if the existence and abundance of these objects are confirmed to be unexpected, the variations in the late-time growth history are unlikely to explain these anomalies.

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Qianran Xia, Dragan Huterer, Nhat-Minh Nguyen. 2025-02-28. Late-time growth weakly affects the significance of high-redshift massive galaxies. https://doi.org/10.33232/001c.137793

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