The<scp>thesan</scp>project: ionizing escape fractions of reionization-era galaxies

A fundamental requirement for reionizing the Universe is that a sufficient fraction of ionizing photons emitted by galaxies successfully escapes into intergalactic medium. However, due to scarcity high-redshift observational data, sources driving reionization remain uncertain. In this work we calculate escape fractions ($f_{\rm esc}$) reionization-era from state-of-the-art THESAN simulations, which combine an accurate radiation-hydrodynamic solver AREPO-RT with well-tested IllustrisTNG galaxy formation model self-consistently simulate both small-scale physics and large-scale throughout large patch universe ($L_{\rm box} = 95.5\,\rm cMpc$). This allows numerous massive haloes ($M_{\rm halo} \gtrsim 10^{10}\,{\rm M_{\odot}}$), are often statistically underrepresented in previous studies but believed be important achieve rapid reionization. We find low-mass stars} \lesssim 10^7\,{\rm M_{\odot}}$) main drivers above $z 7$, while high-mass 10^8\,{\rm dominate escaped photon budget at lower redshifts. The variation halo decreases higher-mass haloes, can understood more settled galactic structure, SFR stability, sightlines within each significantly contributing flux. show dust capable reducing galaxies, impact on global $f_{\rm esc}$ depends model. Finally, AGN unimportant their than stellar ones being located near centres gravitational potential wells.