Astraeus VII: the environmental-dependent assembly of galaxies in the Epoch of Reionization

ABSTRACT Using the astraeus (seminumerical rAdiative tranSfer coupling of galaxy formaTion and Reionization in N-body dark matter simUlationS) framework, we explore impact environmental density radiative feedback on assembly galaxies their host haloes during Epoch Reionization. The framework allows us to study evolution with masses ($10^{8.2}\,\rm M_\odot \lt M_{\rm h}\lt 10^{13}\,\rm M_\odot$) a wide variety environment [−0.5 < log (1 + δ) 1.3 averaged over (2 cMpc)3]. We find that: (i) there exists mass- redshift- dependent ‘characteristic’ [${\rm log}\, (1+\delta _a(M_{\rm h}, z)) = 0.021\times (M_{\rm h}/\rm M_\odot)^{0.16} 0.07 z -1.12$, up $z$ ∼ 10] at which are most efficient accreting matter, e.g rate $0.2{{\ \rm per\ cent}}$ mass every Myr 5; (ii) number minor major mergers contributions increases halo all redshifts is mostly independent environment; (iii) 5 contribute slightly more (by $\sim 10{{\ cent}}$) while for stellar assembly, dominate contribution from $M_{\rm h}\lesssim 10^{11.5}\rm\, M_\odot$ galaxies; (iv) quenches star formation low-mass ($M_{\rm 10^{9.5}\rm\, over-dense environments [log(1 > 0.5]; dominated by branch, this yields histories biased towards older ages slower redshift evolution.