The Structure of Reionization in Hierarchical Galaxy Formation Models

Abstract

Understanding the epoch of reionization and the properties of the first galaxies represents an important goal for modern cosmology. The structure of reionization, and hence the observed power spectrum of redshifted 21cm fluctuations are known to be sensitive to the astrophysical properties of the galaxies that drove reionization. Thus, detailed measurements of the 21cm power spectrum and its evolution could lead to measurements of the properties of early galaxies that are otherwise inaccessible. In this paper, we make predictions for the ionised structure during reionization and the 21cm power spectrum based on detailed models of galaxy formation. We combine the semi-analytic GALFORM model implemented within the Millennium-II dark matter simulation, with a semi-numerical scheme to describe the resulting ionization structure. Using these models we show that the details of SNe and radiative feedback affect the structure and distribution of ionised regions, and hence the slope and amplitude of the 21 cm power spectrum. These results indicate that forthcoming measurements of the 21cm power-spectrum could be used to uncover details of early galaxy formation. We find that the strength of SNe feedback is the dominant effect governing the evolution of structure during reionization. In particular we show SNe feedback to be more important than radiative feedback, the presence of which we find does not influence either the total stellar mass or overall ionising photon budget. Thus, if SNe feedback is effective at suppressing star formation in high redshift galaxies, we find that photoionization feedback does not lead to self-regulation of the reionization process as has been thought.

14 pages, 11 figures, Accepted to MNRAS. Updated version with substantial additions, including implementation of the reionization model within the Millennium-II simulation and self consistent treatment of radiative feedback

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Cited by in corpus (16)

• Semi-analytic forecasts for JWST - I. UV luminosity functions at z = 4 - 10
• Dark-ages reionization and galaxy formation simulation - III. Modelling galaxy formation and the epoch of reionization
• The accuracy of semi-numerical reionization models in comparison with radiative transfer simulations
• Studying topological structure in the epoch of reionization with 3D-Minkowski functionals of 21cm line fluctuations
• Dark-ages reionization & galaxy formation simulation V: morphology and statistical signatures of reionization
• The spatial distribution of neutral hydrogen as traced by low HI mass galaxies
• The cross-power spectrum between 21cm emission and galaxies in hierarchical galaxy formation models
• High resolution simulations of the reionization of an isolated Milky Way - M31 galaxy pair
• The clustering and halo occupation distribution of Lyman-break galaxies at $z\sim 4$
• Cornering Extended Starobinsky Inflation with CMB and SKA
• Two-dimensional Topology of Cosmological Reionization
• Variation in the escape fraction of ionising photons from galaxies and the redshifted 21-cm power spectrum during reionization
• A hybrid multi resolution scheme to efficiently model the structure of reionization on the largest scales
• Accelerating HI density predictions during the Epoch of Reionization using a GPR-based emulator on N-body simulations
• Probing the Inflaton Potential with SKA
• Galaxy Formation & Dark Matter Modelling in the Era of the Square Kilometre Array