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The inhomogeneous reionization times of present-day galaxies

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journal contribution
posted on 2023-06-09, 13:39 authored by Dominique Aubert, Nicolas Deparis, Pierre Ocvirk, Paul R Shapiro, Ilian IlievIlian Iliev, Gustavo Yepes, Stefan Gottlöber, Yehuda Hoffman, Romain Teyssier
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).

Funding

Astronomy rolling grant; G0278; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/I000976/1

STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/F002858/1

History

Publication status

  • Published

File Version

  • Published version

Journal

The Astrophysical Journal

ISSN

2041-8213

Publisher

American Astronomical Society

Issue

2

Volume

856

Page range

1-6

Department affiliated with

  • Physics and Astronomy Publications

Research groups affiliated with

  • Astronomy Centre Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2018-06-06

First Open Access (FOA) Date

2018-06-06

First Compliant Deposit (FCD) Date

2018-06-06

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