Doughty, CaitlinFinlator, KristianOppenheimer, Benjamin D.Dave, RomeelZackrisson, Erik2018-05-152018-05-152018Doughty, 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): 4717–47270035-8711http://dx.doi.org/10.1093/mnras/sty156http://hdl.handle.net/10566/3667We 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.enThis is the pre-print version of the article published online at: http://dx.doi.org/10.1093/mnras/sty156GalaxiesEvolutionFormationHigh-redshiftIntergalactic mediumQuasarsArticle