The O BELISK simulation: Galaxies contribute more than AGN to H※ i reionization of protoclusters

Maxime Trebitsch, Yohan Dubois, Marta Volonteri, Hugo Pfister, Corentin Cadiou, Harley Katz, Joakim Rosdahl, Taysun Kimm, Christophe Pichon, Ricarda S. Beckmann, Julien Devriendt, Adrianne Slyz

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21 Citations (Scopus)


We present the OBELISK project, a cosmological radiation-hydrodynamics simulation that follows the assembly and reionization of a protocluster progenitor during the first two billion years after the big bang, down to z = 3.5. The simulation resolves haloes down to the atomic cooling limit and tracks the contribution of different sources of ionization: stars, active galactic nuclei, and collisions. The OBELISK project is specifically designed to study the coevolution of high-redshift galaxies and quasars in an environment favouring black hole growth. In this paper, we establish the relative contribution of these two sources of radiation to reionization and their respective role in establishing and maintaining the high-redshift ionizing background. Our volume is typical of an overdense region of the Universe and displays star formation rate and black hole accretion rate densities similar to those of high-redshift protoclusters. We find that hydrogen reionization happens inside-out, is completed by z ∼ 6 in our overdensity, and is predominantly driven by galaxies, while accreting black holes only play a role at z ∼ 4.

Original languageEnglish
Article numberA154
JournalAstronomy and Astrophysics
Publication statusPublished - 2021 Sept 1

Bibliographical note

Funding Information:
Strategy EXC-2181/1 - 390900948 (the Heidelberg STRUCTURES Cluster of Excellence). HP is indebted to the Danish National Research Foundation (DNRF132) and the Hong Kong government (GRF grant HKU27305119) for support. TK was supported in part by the Yonsei University Future-leading Research Initiative (RMS2-2019-22-0216) and in part by the National Research Foundation of Korea (No. 2017R1A5A1070354 and No. 2018R1C1B5036146). CC has received partial funding from the Institut Lagrange Paris (ILP) and is supported by the European Union’s Horizon 2020 research and innovation programme (under grant agreement No. 818085 GMGalaxies). This work has made use of the Horizon Cluster hosted by Institut d’Astrophysique de Paris; we thank Stéphane Rouberol for running smoothly this cluster for us. We acknowledge PRACE for awarding us access to Joliot Curie at GENCI@CEA, France, which was used to run most of the simulations presented in this work. Additionally, this work was granted access to the HPC resources of CINES under allocations A0040406955 and A0040407637 made by GENCI. This work has made extensive use of the Yt analysis package Turk et al. (2011) and NASA’s Astrophysics Data System, as well as the Matplotlib Hunter (2007), Numpy/Scipy Jones et al. (2001) and IPython Perez & Granger (2007) packages.

Funding Information:
Acknowledgements. We would like to thank the referee for their useful comments which have strongly improved the readability of this paper. We would like to thank Rebekka Bieri, Jérémy Blaizot, Sam Geen, Mélanie Habouzit, Sandrine Lescaudron and Pierre Ocvirk for helpful comments and stimulating discussions on this work, and over the inception of the Obelisk project in general. This work made use of v2.2.1 of the Binary Population and Spectral Synthesis (Bpass) models as described in Eldridge et al. (2017) and Stanway & Eldridge (2018). We also used the models produced by Kulkarni (2019). MT and MV acknowledge funding from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013 Grant Agreement no. 614199, project ‘BLACK’). MT is supported by Deutsche Forschungsge-meinschaft (DFG, German Research Foundation) under Germany’s Excellence

Publisher Copyright:
© 2021 ESO.

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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