Publication Date:
2013-11-14
Description:
We use a radiation hydrodynamic simulation of the hydrogen reionization epoch to study O i absorbers at z ~ 6. The intergalactic medium (IGM) is reionized before it is enriched; hence, O i absorption originates within dark matter haloes. The predicted abundance of O i absorbers is in reasonable agreement with observations. At z = 10, 70 per cent of sightlines through atomically cooled haloes encounter a visible (N O I 〉 10 14 cm –2 ) column. Reionization ionizes and removes gas from haloes less massive than 10 8.4 M , but 20 per cent of sightlines through more massive haloes encounter visible columns even at z = 5. The mass scale of absorber host haloes is 10–100 times smaller than the haloes of Lyman-break galaxies and Lyman α emitters, hence absorption probes the dominant ionizing sources more directly. O i absorbers have neutral hydrogen columns of 10 19 –10 21 cm –2 , suggesting a close resemblance between objects selected in O i and H i absorption. Finally, the absorption in the foreground of the z = 7.085 quasar ULAS J1120+0641 cannot originate in a dark matter halo because halo gas at the observed H i column density is enriched enough to violate the upper limits on the O i column. By contrast, gas at less than one-third the cosmic mean density satisfies the constraints. Hence, the foreground absorption likely originates in the IGM.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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