Abstract
We use observations of spatially aligned CII, CIV, SiII, SiIV, and OI absorbers to probe the slope and intensity of the ultraviolet background (UVB) at z ~ 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 multifrequency radiative transfer; a soft, spatially uniform UVB; and a hard, spatially uniform 'quasars-only' model. When considering our paired high-ionization absorbers (CIV/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, whereas two more (CII/C IV and OI/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.
Original language | English (US) |
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Pages (from-to) | 4717-4727 |
Number of pages | 11 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 475 |
Issue number | 4 |
DOIs | |
State | Published - Apr 21 2018 |
Keywords
- Cosmology: theory
- Galaxies: evolution
- Galaxies: formation
- Galaxies: high-redshift
- Intergalactic medium
- Quasars: absorption lines
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science