CPC Seminar: Hydrodynamical simulations of the first stars in the cold and fuzzy dark matter cosmologies

  • May 1, 2023, 2:00 pm US/Central
  • Curia II
  • Mihir Kulkarni, University of Toledo
  • Host: Dylan Temples, dtemples@fnal.gov


In the standard model of cosmology with cold dark matter (CDM), the first stars are expected to form in dark matter minihalos of mass 10^5-10^7 Msun. The formation of the first stars can be delayed depending on the feedback processes and environment. We provide a fit for the minimum dark matter halo mass required to form the first stars as a function of the Lyman-Werner radiation, baryon-dark matter streaming velocity, and redshift using a large statistical sample that can be used in the analytic models of first stars and galaxies. Fuzzy dark matter (FDM) is a proposed modification for the standard CDM model motivated by small-scale discrepancies in low-mass galaxies. Composed of ultra-light (mass ∼10^−22  eV) axions that have their quantum effects manifest on the astrophysical scales, this is one of a class of candidates that predicts that the first collapsed objects form in relatively massive dark matter halos. This implies that the formation history of the first stars and galaxies would be very different,  potentially placing strong constraints on such models. I will describe our numerical simulations of the formation of the first stars in an FDM  cosmology, following the collapse in a representative volume all the way down to primordial protostar formation including a primordial non-equilibrium chemical network and cooling for the first time. We find two novel results: first, the large-scale collapse results in a very thin and flat gas “pancake”; second, despite the very different cosmology, this pancake fragments until it forms protostellar objects indistinguishable from those in CDM. Combined, these results indicate that the first generation of stars in this model are also likely to be massive and, because of the sheet morphology, do not self-regulate,  resulting in a massive Pop III starburst. These predictions provide a potential smoking gun signature of FDM and similar dark matter candidates.