Book Description

We use cosmological hydrodynamic simulations to study the impact ofoutflows and radiative feedback on high-redshift galaxies. For outflows, we consider simulations that assume (i) no winds, (ii) a c̀̀onstant-wind"model in which the mass-loading factor and outflow speed areconstant, and (iii) m̀̀omentum-driven" winds in which both parametersvary smoothly with mass. In order to treat radiative feedback, wedevelop a moment-based radiative transfer technique that operates inboth post-processing and coupled radiative hydrodynamic modes. We first ask how outflows impact the broadband spectral energydistributions (SEDs) of six observed reionization-epoch galaxies. Simulations reproduce five regardless of the outflow prescription, while the sixth suggests an unusually bursty star formation history. We conclude that (i) simulations broadly account for available constraintson reionization-epoch galaxies, (ii) individual SEDs do not constrainoutflows, and (iii) SED comparisons efficiently isolate objects thatchallenge simulations. We next study how outflows impact the galaxy mass metallicity relation(MZR). Momentum-driven outflows uniquely reproduce observations at z=2. In this scenario, galaxies obey two equilibria: (i) The rate at which agalaxy processes gas into stars and outflows tracks its inflow rate; and(ii) The gas enrichment rate owing to star formation balances the dilutionrate owing to inflows. Combining these conditions indicates that the MZRis dominated by the (instantaneous) variation of outflows with mass, withmore-massive galaxies driving less gas into outflows per unit stellar massformed. Turning to radiative feedback, we use post-processing simulations to studythe topology of reionization. Reionization begins in overdensities andthen l̀̀eaks" directly into voids, with filaments reionizing last owing totheir high density and low emissivity. This result conflicts withprevious findings that voids ionize last. We argue that it owes to theuniqely-biased emissivity field produced by our star formation prescriptions, which have previously been shown to reproduce numerous post-reionizationconstraints. Finally, preliminary results from coupled radiative hydrodynamicsimulations indicate that reionization suppresses the star formation ratedensity by at most 10--20% by z=5. This is much less than previousestimates, which we attribute to our unique reionization topology althoughconfirmation will have to await more detailed modeling.