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Arxiv: The FLAMINGO simulation view of cluster progenitors observed in the epoch of reionization with JWST Published: 2/27/2024 9:00:00 PM Updated: 7/24/2024 3:59:10 PM

Paper abstract: Motivated by the recent JWST discovery of galaxy overdensities during theEpoch of Reionzation, we examine the physical properties of high-zprotoclusters and their evolution using the FLAMINGO simulation suite. Weinvestigate the impact of the apertures used to define protoclusters, becausethe heterogeneous apertures used in the literature have limited ourunderstanding of the population. Our results are insensitive to theuncertainties of the subgrid models at a given resolution, whereas furtherinvestigation into the dependence on numerical resolution is needed. Whenconsidering galaxies more massive than M_\ast\,{~eq}\,10^8\,{\rm M_\odot},the FLAMINGO simulations predict a dominant contribution from progenitorssimilar to those of the Coma cluster to the cosmic star-formation rate densityduring the reionization epoch. Our results indicate the onset of suppression ofstar formation in the protocluster environments as early as z\,{~eq}\,5.The galaxy number density profiles are similar to NFW at z\,{<~}\,1while showing a steeper slope at earlier times before the formation of thecore. Different from most previous simulations, the predicted star-formationhistory for individual protoclusters is in good agreement with observations. Wedemonstrate that, depending on the aperture, the integrated physical propertiesincluding the total (dark matter and baryonic) mass can be biased by a factorof 2 to 5 at z\,{=}\,5.5--7, and by an order of magnitude atz\,{<~}\,4. This correction suffices to remove the{~eq}\,3\,\sigma tensions with the number density of structures found inrecent JWST observations.