TY - JOUR
T1 - ArtIST
T2 - Fast radiative transfer for large-scale simulations of the epoch of reionization
AU - Molaro, Margherita
AU - Davé, Romeel
AU - Hassan, Sultan
AU - Santos, Mario G.
AU - Finlator, Kristian
N1 - Funding Information:
Our simulations were run on the following computing facilities: the Pumba Astrophysics Computing Cluster, hosted at the University of the Western Cape (UWC), which was generously funded by UWC’s Office of the Deputy Vice Chancellor; and the ilify cloud computing facility, hosted at the University of Cape Town (UCT) as a partnership between UCT, UWC, the University of Stellenbosch, Sol Plaatje University, the Cape Peninsula University of Technology, and the South African Radio Astronomy Observatory. The ilifu facility is supported by contributions from the Inter-University Institute for Data Intensive Astronomy (IDIA - a partnership between UCT, UWC, and the University of Pretoria), the Computational Biology division at UCT, and the Data Intensive Research Initiative of South Africa (DIRISA). The Technicolor simulations used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. RD acknowledges support from the Wolfson Research Merit Award programme of the UK Royal Society. We thank the anonymous referee for the very useful feedback on our draft, which helped us improve our paper.
Publisher Copyright:
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2019/11/11
Y1 - 2019/11/11
N2 - We introduce the ‘Asymmetric Radiative Transfer In Shells Technique’ (ARTIST), a new method for photon propagation on large scales that explicitly conserves photons, propagates photons at the speed of light, approximately accounts for photon directionality, and closely reproduces results of more detailed radiative transfer (RT) methods. Crucially, it is computationally fast enough to evolve the large cosmological volumes required to predict the 21cm power spectrum on scales that will be probed by future experiments targeting the epoch of reionization (EoR). Most seminumerical models aimed at predicting the EoR 21cm signal on these scales use an excursion set formalism (ESF) to model the gas ionization, which achieves computational viability by making a number of approximations. While ARTIST is still roughly two orders of magnitude slower than ESF, it does allow to model the EoR without the need for such approximations. This is particularly important when considering a wide range of reionization scenarios for which ARTIST would help limit the assumptions made. By implementing our RT method within the seminumerical code SIMFAST21, we show that ARTIST predicts a significantly different evolution for the EoR ionization field compared to the code’s native ESF. In particular, ARTIST predicts up to a factor of two difference in the power spectra, depending on the physical parameters assumed. Its application to large-scale EoR simulations will therefore allow more physically motivated constraints to be obtained for key EoR parameters. In particular, it will remove the need for the artificial rescaling of the escape fraction.
AB - We introduce the ‘Asymmetric Radiative Transfer In Shells Technique’ (ARTIST), a new method for photon propagation on large scales that explicitly conserves photons, propagates photons at the speed of light, approximately accounts for photon directionality, and closely reproduces results of more detailed radiative transfer (RT) methods. Crucially, it is computationally fast enough to evolve the large cosmological volumes required to predict the 21cm power spectrum on scales that will be probed by future experiments targeting the epoch of reionization (EoR). Most seminumerical models aimed at predicting the EoR 21cm signal on these scales use an excursion set formalism (ESF) to model the gas ionization, which achieves computational viability by making a number of approximations. While ARTIST is still roughly two orders of magnitude slower than ESF, it does allow to model the EoR without the need for such approximations. This is particularly important when considering a wide range of reionization scenarios for which ARTIST would help limit the assumptions made. By implementing our RT method within the seminumerical code SIMFAST21, we show that ARTIST predicts a significantly different evolution for the EoR ionization field compared to the code’s native ESF. In particular, ARTIST predicts up to a factor of two difference in the power spectra, depending on the physical parameters assumed. Its application to large-scale EoR simulations will therefore allow more physically motivated constraints to be obtained for key EoR parameters. In particular, it will remove the need for the artificial rescaling of the escape fraction.
KW - First stars
KW - Radiative transfer – dark ages
KW - Reionization
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U2 - 10.1093/mnras/stz2171
DO - 10.1093/mnras/stz2171
M3 - Article
AN - SCOPUS:85075253393
VL - 489
SP - 5594
EP - 5611
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -