Selfconsistent Modeling of Reionization in Cosmological Hydrodynamical Simulations
Abstract
The ultraviolet background (UVB) emitted by quasars and galaxies governs the ionization and thermal state of the intergalactic medium (IGM), regulates the formation of highredshift galaxies, and is thus a key quantity for modeling cosmic reionization. The vast majority of cosmological hydrodynamical simulations implement the UVB via a set of spatially uniform photoionization and photoheating rates derived from UVB synthesis models. In this paper, we show that simulations using canonical UVB rates reionize and, perhaps more importantly, spuriously heat the IGM, much earlier ($$z\sim 15$$) than they should. This problem arises because at $$z\gt 6$$, where observational constraints are nonexistent, the UVB amplitude is far too high. We introduce a new methodology to remedy this issue, and we generate selfconsistent photoionization and photoheating rates to model any chosen reionization history. Following this approach, we run a suite of hydrodynamical simulations of different reionization scenarios and explore the impact of the timing of reionization and its concomitant heat injection on the thermal state of the IGM. We present a comprehensive study of the pressure smoothing scale of IGM gas, illustrating its dependence on the details of both hydrogen and helium reionization, and argue that it plays a fundamental role in interpreting Lyα forest statistics and the thermal evolution of the IGM. The premature IGM heating we have uncovered implies that previous work has likely dramatically overestimated the impact of photoionization feedback on galaxy formation, which sets the minimum halo mass able to form stars at high redshifts. Finally, we make our new UVB photoionization and photoheating rates publicly available for use in future simulations.
 Authors:
 Max Planck Inst. for Astronomy, Heidelberg (Germany)
 Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
 Publication Date:
 Research Org.:
 Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Max Planck Inst. for Astronomy, Heidelberg (Germany)
 Sponsoring Org.:
 USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC21); USDOE Office of Science (SC), High Energy Physics (HEP) (SC25); Alexander von Humboldt Foundation (Germany); German Federal Ministry of Education and Research (BMBF)
 OSTI Identifier:
 1379770
 Grant/Contract Number:
 AC0205CH11231
 Resource Type:
 Journal Article: Accepted Manuscript
 Journal Name:
 The Astrophysical Journal (Online)
 Additional Journal Information:
 Journal Name: The Astrophysical Journal (Online); Journal Volume: 837; Journal Issue: 2; Journal ID: ISSN 15384357
 Publisher:
 Institute of Physics (IOP)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTRONOMY AND ASTROPHYSICS; early universe; evolution of galaxies; formation of galaxies; intergalactic medium; largescale structure of universe; numerical methods
Citation Formats
Oñorbe, Jose, Hennawi, Joseph F., and Lukić, Zarija. Selfconsistent Modeling of Reionization in Cosmological Hydrodynamical Simulations. United States: N. p., 2017.
Web. doi:10.3847/15384357/aa6031.
Oñorbe, Jose, Hennawi, Joseph F., & Lukić, Zarija. Selfconsistent Modeling of Reionization in Cosmological Hydrodynamical Simulations. United States. doi:10.3847/15384357/aa6031.
Oñorbe, Jose, Hennawi, Joseph F., and Lukić, Zarija. Wed .
"Selfconsistent Modeling of Reionization in Cosmological Hydrodynamical Simulations". United States.
doi:10.3847/15384357/aa6031. https://www.osti.gov/servlets/purl/1379770.
@article{osti_1379770,
title = {Selfconsistent Modeling of Reionization in Cosmological Hydrodynamical Simulations},
author = {Oñorbe, Jose and Hennawi, Joseph F. and Lukić, Zarija},
abstractNote = {The ultraviolet background (UVB) emitted by quasars and galaxies governs the ionization and thermal state of the intergalactic medium (IGM), regulates the formation of highredshift galaxies, and is thus a key quantity for modeling cosmic reionization. The vast majority of cosmological hydrodynamical simulations implement the UVB via a set of spatially uniform photoionization and photoheating rates derived from UVB synthesis models. In this paper, we show that simulations using canonical UVB rates reionize and, perhaps more importantly, spuriously heat the IGM, much earlier ($z\sim 15$) than they should. This problem arises because at $z\gt 6$, where observational constraints are nonexistent, the UVB amplitude is far too high. We introduce a new methodology to remedy this issue, and we generate selfconsistent photoionization and photoheating rates to model any chosen reionization history. Following this approach, we run a suite of hydrodynamical simulations of different reionization scenarios and explore the impact of the timing of reionization and its concomitant heat injection on the thermal state of the IGM. We present a comprehensive study of the pressure smoothing scale of IGM gas, illustrating its dependence on the details of both hydrogen and helium reionization, and argue that it plays a fundamental role in interpreting Lyα forest statistics and the thermal evolution of the IGM. The premature IGM heating we have uncovered implies that previous work has likely dramatically overestimated the impact of photoionization feedback on galaxy formation, which sets the minimum halo mass able to form stars at high redshifts. Finally, we make our new UVB photoionization and photoheating rates publicly available for use in future simulations.},
doi = {10.3847/15384357/aa6031},
journal = {The Astrophysical Journal (Online)},
number = 2,
volume = 837,
place = {United States},
year = {Wed Mar 08 00:00:00 EST 2017},
month = {Wed Mar 08 00:00:00 EST 2017}
}
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