The inhomogeneous reionization times of present-day galaxies

Aubert, Dominique, Deparis, Nicolas, Ocvirk, Pierre, Shapiro, Paul R, Iliev, Ilian T, Yepes, Gustavo, Gottlöber, Stefan, Hoffman, Yehuda and Teyssier, Romain (2018) The inhomogeneous reionization times of present-day galaxies. The Astrophysical Journal, 856 (2). pp. 1-6. ISSN 2041-8213

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Abstract

Today's galaxies experienced cosmic reionization at different times in different locations. For the first time, reionization (50% ionized) redshifts, z R , at the location of their progenitors are derived from new, fully coupled radiation-hydrodynamics simulation of galaxy formation and reionization at z > 6, matched to N-body simulation to z = 0. Constrained initial conditions were chosen to form the well-known structures of the local universe, including the Local Group and Virgo, in a (91 Mpc)3 volume large enough to model both global and local reionization. Reionization simulation CoDa I-AMR, by CPU-GPU code EMMA, used (2048)3 particles and (2048)3 initial cells, adaptively refined, while N-body simulation CoDa I-DM2048, by Gadget2, used (2048)3 particles, to find reionization times for all galaxies at z = 0 with masses M(z = 0) ≥ 108 M ⊙. Galaxies with $M(z=0)\gtrsim {10}^{11}\,{M}_{\odot }$ reionized earlier than the universe as a whole, by up to ~500 Myr, with significant scatter. For Milky Way–like galaxies, z R ranged from 8 to 15. Galaxies with $M(z=0)\lesssim {10}^{11}\,{M}_{\odot }$ typically reionized as late or later than globally averaged 50% reionization at $\langle {z}_{R}\rangle =7.8$, in neighborhoods where reionization was completed by external radiation. The spread of reionization times within galaxies was sometimes as large as the galaxy-to-galaxy scatter. The Milky Way and M31 reionized earlier than global reionization but later than typical for their mass, neither dominated by external radiation. Their most-massive progenitors at z > 6 had z R =9.8 (MW) and 11 (M31), while their total masses had z R = 8.2 (both).

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Astronomy Centre
Subjects: Q Science > QB Astronomy
Depositing User: Billy Wichaidit
Date Deposited: 06 Jun 2018 14:55
Last Modified: 02 Jul 2019 15:32
URI: http://sro.sussex.ac.uk/id/eprint/76363

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Project NameSussex Project NumberFunderFunder Ref
Astronomy rolling grantG0278STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/I000976/1
UnsetUnsetSTFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/F002858/1