Project: Multiscale simulations of Cosmic Reionization

Prace Call: 17th
ID: 2018184382, Leader: Ilian Iliev
Affiliation: University of Sussex, GB
Research Field: Universe Sciences
Collaborators: Hannah Ross University of Sussex UK , Peter Thomas University of Sussex UK , Garrelt Mellema Stockholm University SE , Azizah Hosein University of Sussex UK , Kyungjin Ahn Chosun University KR , Anastasia Fialkov The Harvard Smithsonian Center for Astrophysics USA , Paul Shapiro The University of Texas at Austin USA , Jenny Sorce Lyon University FR , Gustavo Yepes Universidad Autonoma de Madrid ES , Stefan Gottloeber Leibniz Institut fuer Astrophysik Potsdam (AIP) DE , Sergey Pillipenko Lebedev Physical Institute of the RAS RU , Taha Dawoodbhoy The University of Texas at Austin USA , Raghunath Ghara Stockholm University SE , Michele Bianco University of Sussex UK , Rajesh Mondal University of Sussex UK , Keri Dixon New York University Abu Dhabi AE
Resource Awarded: 20.8 Mil. core hours on Marconi - Broadwell


The first billion years of cosmic evolution are one of the last largely uncharted territories in astrophysics. During this key period the cosmic web of structures we see today first started taking shape and the very first stars and galaxies formed. The radiation from these first galaxies started the process of cosmic reionization, which eventually ionized and heated the entire universe, in which state it remains today. This process had profound effects on the formation of cosmic structures and has left a lasting impression on them. This reionization process is inherently multi-scale. It is generally believed to be driven by stellar radiation from low-mass galaxies, which cluster on large scales and collectively create very large ionized patches whose eventual overlap completes the process. The star formation inside such galaxies is strongly affected by complex radiative and hydrodynamic feedback effects, including ionizing and non-ionizing UV radiation, shock waves, gas cooling and heating, stellar winds and enrichment by heavy elements. Understanding the nature of the first galaxies and how they affect the progress, properties and duration of the cosmic reionization requires detailed modelling of these complex interactions.The aim of this project is to combine a unique set of simulations of cosmic reionization covering the full range of relevant scales, from very small, sub-galactic scales, for studying the detailed physics of radiative feedback, all the way to very large cosmological volumes at which the direct observations will be done. These simulations will be bases on state-of-the-art numerical tools, including Adaptive Mesh Refinement (AMR) techniques for achieving very large dynamic range in radiative hydrodynamics calculations (RAMSES-RT code), and a massively-parallel, highly numerically efficient radiative transfer method for accurate modelling at large scales (C2-Ray). We will complement the numerical simulations with semi-analytical galaxy formation modelling to explore the large parameter space available, to improve the treatment of reionizing sources in large-scale radiative transfer simulations as well as to derive detailed observational features of the first galaxies in different observational bands. The questions we will address are: 1) how does the radiative feedback from the First Stars hosted in cosmological minihaloes and dwarf galaxies affect the formation of early structures and subsequent star formation?; 2) how much does high-redshift galaxy formation differ from that at present day? What are the observational signatures of the first galaxies? 3) how important is the recently pointed out effect of local modulation of the star formation in minihaloes due to differential supersonic drift velocities between baryons and dark matter?; 4) how does the metal enrichment and the transition from Pop III (metal-free) to Pop II stars occur locally and how is this reflected in the metallicity distribution of the observed dwarf galaxies and globular clusters? and 5) how do alternative dark matter models affect reionization and do they have any unique observational signatures? and 6) How are these feedback effects imprinted on large-scale observational features?