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
(fesc), we quantify how the contribution of star-forming galaxies
{(with halo masses Mh>108.2M⊙)} to reionization depends on the
radiative feedback model, fesc, and the environmental over-density.
Our key findings are: (i) for constant fesc models,
intermediate-mass galaxies (with halo masses of Mh≃109−11M⊙
and absolute UV magnitudes of MUV∼−15 to −20) in
intermediate-density regions drive reionization; (ii) scenarios where
fesc increases with decreasing halo mass shift the galaxy
population driving reionization to lower-mass galaxies
(Mh≲109.5M⊙) with lower luminosities (MUV≳−16)
and over-densities; (iii) reionization imprints its topology on the ionizing
emissivity of low-mass galaxies (Mh≲109M⊙) 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 fesc 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 MUV=−16) will be able to detect the galaxies providing ∼60−70% (∼10%) of reionization photons at z=7 for constant fesc models
(scenarios where fesc increases with decreasing halo mass).Comment: 14 pages, 13 figures, accepted for publication in MNRA