A population of ultraviolet-dim protoclusters detected in absorption

Abstract

Galaxy protoclusters, which will eventually grow into the massive clusters we see in the local universe, are usually traced by locating overdensities of galaxies. Large spectroscopic surveys of distant galaxies now exist, but their sensitivity depends mainly on a galaxy's star formation activity and dust content rather than its mass. Tracers of massive protoclusters that do not rely on their galaxy constituents are therefore needed. Here we report observations of Lyman-$\alpha$ absorption in the spectra of a dense grid of background galaxies, which we use to locate a substantial number of candidate protoclusters at redshifts 2.2-2.8 via their intergalactic gas. We find that the structures producing the most absorption, most of which were previously unknown, contain surprisingly few galaxies compared to the dark matter content of their analogs in cosmological simulations. Nearly all are expected to be protoclusters, and we infer that half of their expected galaxy members are missing from our survey because they are unusually dim at rest-frame ultraviolet wavelengths. We attribute this to an unexpectedly strong and early influence of the protocluster environment on the evolution of these galaxies that reduced their star formation or increased their dust content.

Published in Nature. The version of record is available at https://www.nature.com/articles/s41586-022-04681-6 or view-only at https://rdcu.be/cPIIX

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Cited by in corpus (14)

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• Observational Evidence for Large-Scale Gas Heating in a Galaxy Protocluster at z=2.30
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• Discovering Large-Scale Structure at $2<z<5$ in the C3VO Survey
• The COSMOS-Web deep galaxy group catalog up to $z=3.7$
• Connecting the growth of galaxies to the large-scale environment in a massive node of the Cosmic Web at z~3
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• Prospects for studying the mass and gas in protoclusters with future CMB observations
• LATIS: Comparing Galaxy and IGM Tomography Maps as Tracers of Large-scale Structure and Protoclusters at $z\sim 2.5$
• The HST-Hyperion Survey: Companion Fraction and Overdensity in a z ~ 2.5 Proto-supercluster
• LATIS Data Release: $\sim 4200$ Spectra of $z\sim 2-3$ Galaxies, Redshifts, and Intergalactic Medium Tomography Maps