Astraeus III: The environment and physical properties of reionization sources

Anne Hutter; Pratika Dayal; Laurent Legrand; Stefan Gottlöber; Gustavo Yepes

doi:10.1093/mnras/stab877

paper

Astraeus III: The environment and physical properties of reionization sources

arXiv:2008.13215 · doi:10.1093/mnras/stab877

Abstract

In this work, we use the {\sc astraeus} (seminumerical rAdiative tranSfer coupling of galaxy formaTion and Reionization in N-body dArk mattEr simUlationS) framework which couples galaxy formation and reionization in the first billion years. Exploring a number of models for reionization feedback and the escape fraction of ionizing radiation from the galactic environment ( $f_{esc}$ ), we quantify how the contribution of star-forming galaxies {(with halo masses $M_{h} > 1 0^{8.2}$ M $_{⊙}$ )} to reionization depends on the radiative feedback model, $f_{esc}$ , and the environmental over-density. Our key findings are: (i) for constant $f_{esc}$ models, intermediate-mass galaxies (with halo masses of $M_{h} ≃ 1 0^{9 - 11}$ M $_{⊙}$ and absolute UV magnitudes of $M_{U V} \sim - 15$ to $- 20$ ) in intermediate-density regions drive reionization; (ii) scenarios where $f_{esc}$ increases with decreasing halo mass shift the galaxy population driving reionization to lower-mass galaxies ( $M_{h} ≲ 1 0^{9.5}$ M $_{⊙}$ ) with lower luminosities ( $M_{U V} ≳ - 16$ ) and over-densities; (iii) reionization imprints its topology on the ionizing emissivity of low-mass galaxies ( $M_{h} ≲ 1 0^{9}$ M $_{⊙}$ ) through radiative feedback. Low-mass galaxies experience a stronger suppression of star formation by radiative feedback and show lower ionizing emissivities in over-dense regions; (iv) a change in $f_{esc}$ with galaxy properties has the largest impact on the sources of reionization and their detectability, with the radiative feedback strength and environmental over-density playing a sub-dominant role; (v) JWST-surveys (with a limiting magnitude of $M_{U V} = - 16$ ) will be able to detect the galaxies providing $\sim 60 - 70%$ ( $\sim 10%$ ) of reionization photons at $z = 7$ for constant $f_{esc}$ models (scenarios where $f_{esc}$ increases with decreasing halo mass).

arXiv comment14 pages, 13 figures, accepted for publication in MNRAS

Astraeus III: The environment and physical properties of reionization sources

Abstract

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