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arXiv · 1801.06193

Aligned metal absorbers and the ultraviolet background at the end of reionization

Caitlin Doughty·Kristian Finlator·Benjamin D. Oppenheimer·Romeel Davé·Erik Zackrisson
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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 $z \sim 6$. We accomplish this by comparing observations with predictions from a cosmological hydrodynamic 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 (C IV/Si IV), the observed statistics strongly prefer the hard, spatially-uniform UVB. This echoes recent findings that cosmological simulations 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 constraints on the UVB.

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Caitlin Doughty, Kristian Finlator, Benjamin D. Oppenheimer, Romeel Davé, Erik Zackrisson. 2018-01-18. Aligned metal absorbers and the ultraviolet background at the end of reionization. https://doi.org/10.1093/mnras%2Fsty156

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