We employ high-resolution cosmological zoom-in simulations focusing on a high-sigma peak and an average cosmological field at z ~ 6–12 in order to investigate the influence of environment and baryonic feedback on galaxy evolution in the reionization epoch. Strong feedback, e.g., galactic winds, caused by elevated star formation rates (SFRs) is expected to play an important role in this evolution. We compare different outflow prescriptions: (i) constant wind velocity (CW), (ii) variable wind scaling with galaxy properties (VW), and (iii) no outflows (NW). The overdensity leads to accelerated evolution of dark matter and baryonic structures, absent from the "normal" region, and to shallow galaxy stellar mass functions at the low-mass end. Although CW shows little dependence on the environment, the more physically motivated VW model does exhibit this effect. In addition, VW can reproduce the observed specific SFR (sSFR) and the sSFR–stellar mass relation, which CW and NW fail to satisfy simultaneously. Winds also differ substantially in affecting the state of the intergalactic medium (IGM). The difference lies in the volume-filling factor of hot, high-metallicity gas, which is near unity for CW, while such gas remains confined in massive filaments for VW, and locked up in galaxies for NW. Such gas is nearly absent from the normal region. Although all wind models suffer from deficiencies, the VW model seems to be promising in correlating the outflow properties with those of host galaxies. Further constraints on the state of the IGM at high z are needed to separate different wind models.

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Published in The Astrophysical Journal, v. 829, no. 2, 71, p. 1-21.

© 2016. The American Astronomical Society. All rights reserved.

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This work has been partially supported by the NSF grant AST-080776, the HST/STScI grant AR-12639.01-A, and JSPS KAKENHI grant #16H02163 (to I.S.). R.S. is partially supported by NSF grant AST-1208891. I.S. is grateful for support from International Joint Research Promotion Program at Osaka University. J.H.C. acknowledges support from NASA ATP NNX11AE09G, NSF AST-1009799, and Caltech/JPL SURP Project No. 1515294 through the UT Austin (P.I. Paul Shapiro). E.R.D. thanks DFG for support under SFB 956. Support for HST/STScI grant was provided by NASA through a grant from the STScI, which is operated by the AURA, Inc., under NASA contract NAS5-26555.