A new analytical formalism self-consistently predicts both the ionized fraction x_i(z) and photoionization rate Gamma_HI(z), achieving percent-level accuracy in x_i and 20-30% accuracy in Gamma_HI versus radiative transfer simulations at z less than or equal to 6.
Cosmic Dawn (CoDa): the First Radiation-Hydrodynamics Simulation of Reionization and Galaxy Formation in the Local Universe
6 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Cosmic reionization by starlight from early galaxies affected their evolution, thereby impacting reionization, itself. Star formation suppression, for example, may explain the observed underabundance of Local Group dwarfs relative to N-body predictions for Cold Dark Matter. Reionization modelling requires simulating volumes large enough [~(100Mpc)^3] to sample reionization "patchiness", while resolving millions of galaxy sources above ~10^8 Msun , combining gravitational and gas dynamics with radiative transfer. Modelling the Local Group requires initial cosmological density fluctuations pre-selected to form the well-known structures of the local universe today. Cosmic Dawn ("CoDa") is the first such fully-coupled, radiation-hydrodynamics simulation of reionization of the local universe. Our new hybrid CPU-GPU code, RAMSES-CUDATON, performs hundreds of radiative transfer and ionization rate-solver timesteps on the GPUs for each hydro-gravity timestep on the CPUs. CoDa simulated (91Mpc)^3 with 4096^3 particles and cells, to redshift 4.23, on ORNL supercomputer Titan, utilizing 8192 cores and 8192 GPUs. Global reionization ended slightly later than observed. However, a simple temporal rescaling which brings the evolution of ionized fraction into agreement with observations also reconciles ionizing flux density, cosmic star formation history, CMB electron scattering optical depth and galaxy UV luminosity function with their observed values. Photoionization heating suppressed the star formation of haloes below ~2 x 10^9 Msun , decreasing the abun- dance of faint galaxies around MAB_1600 = [-10,-12]. For most of reionization, star formation was dominated by haloes between 10^10 - 10^11 Msun , so low-mass halo suppression was not reflected by a distinct feature in the global star formation history. (Abridged)
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Using lensed JWST data behind Abell S1063, the UVLF at z~6-11 is fit with gradual quadratic turnover, yielding no evidence for turnover to M_UV=-13.5 at z=6, exclusion limits on turnover models, and lower bounds showing faint galaxies contribute >50% of UV luminosity density and ~64% of ionizing pho
Simulations show recombination-weighted clumping is systematically lower than density-based measures, density-only prescriptions overpredict rates by 1.29-1.84 depending on redshift, and a new phase-space clumping factor isolates thermal and ionization effects at fixed density.
The Lumina simulation shows that explicit light-cone integrations produce a CMB optical depth 7% higher than volume-weighted ionization histories, with the excess accumulating near redshift 8 and mass-weighted estimates capturing most of the difference.
Simulations of high-redshift galaxies show the 1719 Å UV index reliably traces stellar metallicity while others are more sensitive to star formation history.
An updated linear halo bias fit calibrated on high-redshift simulations reduces systematic offsets in early-universe clustering predictions to under 1%.
citing papers explorer
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A self-consistent analytical model for both the photoionization rate and reionization history
A new analytical formalism self-consistently predicts both the ionized fraction x_i(z) and photoionization rate Gamma_HI(z), achieving percent-level accuracy in x_i and 20-30% accuracy in Gamma_HI versus radiative transfer simulations at z less than or equal to 6.
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Tilting at the Turnover: Modeling the Faint-End of the UV Luminosity Function Behind Abell s1063 with JWST
Using lensed JWST data behind Abell S1063, the UVLF at z~6-11 is fit with gradual quadratic turnover, yielding no evidence for turnover to M_UV=-13.5 at z=6, exclusion limits on turnover models, and lower bounds showing faint galaxies contribute >50% of UV luminosity density and ~64% of ionizing pho
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The Lumina Project: Intergalactic Clumping and Recombination Sinks
Simulations show recombination-weighted clumping is systematically lower than density-based measures, density-only prescriptions overpredict rates by 1.29-1.84 depending on redshift, and a new phase-space clumping factor isolates thermal and ionization effects at fixed density.
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The Lumina Project: CMB Optical Depth Fluctuations from Patchy Reionization
The Lumina simulation shows that explicit light-cone integrations produce a CMB optical depth 7% higher than volume-weighted ionization histories, with the excess accumulating near redshift 8 and mass-weighted estimates capturing most of the difference.
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First Light And Reionization Epoch Simulations (FLARES) XXI: The UV Indices of Galaxies in the Early Universe
Simulations of high-redshift galaxies show the 1719 Å UV index reliably traces stellar metallicity while others are more sensitive to star formation history.
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An Improved Fit for Linear Halo Bias at High Redshift
An updated linear halo bias fit calibrated on high-redshift simulations reduces systematic offsets in early-universe clustering predictions to under 1%.