Aligned metal absorbers and the ultraviolet background at the end of reionization
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford University Press
Abstract
We use observations of spatially-aligned C ii, C iv, Si ii, Si iv, and O i absorbers to probe the
slope and intensity of the ultraviolet background (UVB) at z ∼ 6. We accom- plish this by comparing
observations with predictions from a cosmological hydrody- namic simulation using three trial UVBs
applied in post-processing: a spectrally soft, fluctuating UVB calculated using multi-frequency
radiative transfer; a soft, spatially- uniform UVB; and a hard, spatially-uniform “quasars-only”
model. When considering our paired high-ionization absorbers (Civ/Siiv), the observed statistics
strongly prefer the hard, spatially-uniform UVB. This echoes recent findings that cosmological sim-
ulations generically underproduce strong C iv absorbers at z > 5. A single low/high ionization pair
(Si ii/Si iv), by contrast, shows a preference for the HM12 UVB, while two more (C ii/C iv and O
i/C iv) show no preference for any of the three UVBs. Despite this, future observations of specific
absorbers, particularly Si iv/C iv, with next-generation telescopes probing to lower column
densities should yield tighter con-
ts on the UVB.
Description
Keywords
Galaxies, Evolution, Formation, High-redshift, Intergalactic medium, Quasars
Citation
Doughty, C. et al. (2018). Aligned metal absorbers and the ultraviolet background at the end of reionization. Monthly Notices of the Royal Astronomical Society, 475(4): 4717–4727