The z ~ 3 epoch represents a putative turning point in the evolution of the progenitors of galaxy clusters, when the accretion of cold baryons onto the largest dark matter halos becomes inefficient due to the warming intrahalo medium. Nevertheless, the diffuse intrahalo gas at this epoch is far from being as uniformly hot as the intracluster medium (ICM) of their descendant structures in the contemporary universe. The near-ubiquitous detection of giant Lyman-alpha nebulae in protoclusters indeed points to the presence of significant quantities of colder gas coexisting with the incipient hot ICM. This cold/warm gas can be traced either directly through Lyman alpha emission or, farther away from excitation sources, as absorption in the spectrum of background sources. Here I will discuss it both from a theoretical perspective and observationally, through a VLT/MUSE follow-up of the NICE protocluster sample.
Contact local & organization: Emanuele DADDI
DAp