Galaxy protoclusters, the progenitors of today’s massive galaxy clusters, assemble over the first few billion years of cosmic history. They are notoriously hard to identify as their members are spread over megaparsec scales, diluted by unrelated field galaxies, and only stand out as modest density contrasts at high redshift. Simulations face a different problem: the computational cost of realistic galaxy physics has traditionally limited run volumes, forcing a choice between well-resolved but narrow simulations and large, statistical samples with only simplified galaxy models. I use the large-volume hydrodynamical simulation MillenniumTNG, which combines a big enough box for a statistical cluster sample with full hydrodynamics and access to the mean field, to model realistic galaxy populations without a long chain of assumptions and test how reliably different observational selection methods recover protoclusters and their eventual cluster masses. I then compare these predictions to multi-wavelength observations of protocluster candidates selected around biased tracers such as quasars, assessing how likely these structures are to collapse into galaxy clusters, and what mass they are likely to reach.
Local contact: Thierry FOGLIZZO
Organisation: Jérôme Guilet