Variation in the escape fraction of ionising photons from galaxies and the redshifted 21-cm power spectrum during reionization

Abstract

The observed power spectrum of redshifted 21cm fluctuations is 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 study the effect of mass and redshift dependent escape fractions of ionizing radiation on the ability of forthcoming experiments to constrain galaxy formation via the redshifted 21cm power spectrum. We use a model for reionization which combines the hierarchical galaxy formation model GALFORM implemented within the Millennium-II dark matter simulation, with a semi-numerical scheme to describe the resulting ionization structure. Using this model we show that the structure and distribution of ionised regions at fixed neutral fraction, and hence the slope and amplitude of the 21 cm power spectrum, is dependent on the variation of ionising photon escape fraction with galaxy mass and redshift. However, we find that the influence of the unknown escape fraction and its evolution is smaller than the dominant astrophysical effect provided by SNe feedback strength in high redshift galaxies. The unknown escape fraction of ionizing radiation from galaxies is therefore unlikely to prevent measurement of the properties of high redshift star formation using observations of the 21cm power spectrum.

8 pages, 5 figures, Submitted to MNRAS. arXiv admin note: substantial text overlap with arXiv:1203.3598

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Cited by in corpus (10)

• Dark-ages reionization and galaxy formation simulation - III. Modelling galaxy formation and the epoch of reionization
• The 21cm bispectrum during reionization: a tracer of the ionization topology
• Distinguishing models of reionization using future radio observations of 21-cm 1-point statistics
• Dark-ages reionization & galaxy formation simulation V: morphology and statistical signatures of reionization
• The Escape Fraction of Ionizing Photons During the Epoch of Reionization: observability with the Square Kilometre Array
• The Indirect Influence of Quasars on Reionization
• The HI mass function as a probe of photoionisation feedback on low mass galaxy formation
• Astraeus VIII: A new framework for Lyman-$\alpha$ emitters applied to different reionisation scenarios
• A hybrid multi resolution scheme to efficiently model the structure of reionization on the largest scales
• Thinking outside the halo: Tracing the large-scale distribution of diffuse cosmic metals with semi-analytic models