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ABSTRACT We present the Sherwood–Relics simulations, a new suite of large cosmological hydrodynamical simulations aimed at modelling the intergalactic medium (IGM) during and after the cosmic reionization of hydrogen. The suite consists of over 200 simulations that cover a wide range of astrophysical and cosmological parameters. It also includes simulations that use a new lightweight hybrid scheme for treating radiative transfer effects. This scheme follows the spatial variations in the ionizing radiation field, as well as the associated fluctuations in IGM temperature and pressure smoothing. It is computationally much cheaper than full radiation hydrodynamics simulations, and circumvents the difficult task of calibrating a galaxy formation model to observational constraints on cosmic reionization. Using this hybrid technique, we study the spatial fluctuations in IGM properties that are seeded by patchy cosmic reionization. We investigate the relevant physical processes and assess their impact on the z > 4 Lyman-α forest. Our main findings are: (i) consistent with previous studies patchy reionization causes large-scale temperature fluctuations that persist well after the end of reionization, (ii) these increase the Lyman-α forest flux power spectrum on large scales, and (iii) result in a spatially varying pressure smoothing that correlates well with the local reionization redshift. (iv) Structures evaporated or puffed up by photoheating cause notable features in the Lyman-α forest, such as flat-bottom or double-dip absorption profiles.
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Inhomogeneous He ii reionization in hydrodynamic simulations
ABSTRACT The reionization of the second electron of helium shapes the physical state of intergalactic gas at redshifts between 2 ≲ z ≲ 5. Because performing full in situ radiative transfer in hydrodynamic simulations is computationally expensive for large volumes, the physics of He ii reionization is often approximated by a uniform ultraviolet background model that does not capture the spatial inhomogeneity of reionization. We have devised a model that implements the effects of He ii reionization using semi-analytic calculations of the thermal state of intergalactic gas – a way to bypass a full radiative transfer simulation while still realizing the physics of He ii reionization that affects observables such as the Lyman α forest. Here, we present a publicly available code that flexibly models inhomogeneous He ii reionization in simulations at a negligible computational cost. Because many of the parameters of He ii reionization are uncertain, our model is customizable from a set of free parameters. We show results from this code in mp-gadget, where this model is implemented. We demonstrate the resulting temperature evolution and temperature–density relation of intergalactic gas – consistent with recent measurements and previous radiative transfer simulations. We show that the impact of He ii reionization gives rise to subtle signatures in the 1D statistics of the Lyman α forest at the level of several percent, in agreement with previous findings. The flexible nature of these simulations is ideal for studies of He ii reionization and future observations of the He ii Lyman α forest.
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- Award ID(s):
- 1817256
- PAR ID:
- 10289364
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 496
- Issue:
- 4
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 4372 to 4382
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/staa1850
