The Inhomogeneous Reionization Times of Present-day Galaxies
[2];
[3];
[4];
[7]
- Univ. de Strasbourg (France)
- Univ. of Texas, Austin, TX (United States)
- Univ. of Sussex, Falmer, Brighton (United Kingdom)
- Univ. Autonoma de Madrid, Cantoblanco (Spain)
- Leibniz-Inst. für Astrophysik Potsdam (AIP), Potsdam (Germany)
- Hebrew Univ., Jerusalem (Israel)
- Univ. of Zurich (Switzerland)
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. Finally, 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).
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- OSTI ID:
- 1565710
- Journal Information:
- The Astrophysical Journal. Letters (Online), Vol. 856, Issue 2; ISSN 2041-8213
- Publisher:
- Institute of Physics (IOP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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