The environment of Quasars at the Cosmic Dawn

17-21 February 2025

Quasars at cosmic dawn are expected to reside in some of the most prominent galaxy overdensities of the cosmic web in the first Gyr of the Universe. After decades-long efforts, only recently observational support for such massive structures has emerged. The goal of this “team research” proposal is to bring together experts in the study of the quasar environment at cosmic dawn both from observational and theoretical perspectives. We will compare the predictions from semi-analytical models with observational constraints for different galaxy selections (based on stellar mass, star formation rates, expected luminosity in different bands or emission lines). We will gauge the number of galactic companions in the fields of high-z quasar hosts as a function of distance from the quasar; test the variance within the quasar population; infer the ultimate evolutionary path for these overdensities; and stress-test models on their demography. Only a tight synergy between observations and models can deliver the expected breakthrough in our understanding of the quasar environment at cosmic dawn.


  • Roberto Decarli (INAF-OAS, Bologna)
  • Fabio Fontanot (INAF-OA, Trieste)


  • TBA