The reionization of carbon

Kristian Finlator, Robert Thompson, Shuiyao Huang, Romeel Davé, E. Zackrisson, B. D. Oppenheimer

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Observations suggest that C II was more abundant than C IV in the intergalactic medium towards the end of the hydrogen reionization epoch (z ˜ 6). This transition provides a unique opportunity to study the enrichment history of intergalactic gas and the growth of the ionizing ultraviolet background (UVB) at early times. We study how carbon absorption evolves from z = 10 to 5 using a cosmological hydrodynamic simulation that includes a self-consistent multifrequency UVB as well as a well-constrained model for galactic outflows to disperse metals. Our predicted UVB is within ˜2-4 times of that from Haardt & Madau, which is fair agreement given the uncertainties. Nonetheless, we use a calibration in post-processing to account for Lyman α forest measurements while preserving the predicted spectral slope and inhomogeneity. The UVB fluctuates spatially in such a way that it always exceeds the volume average in regions where metals are found. This implies both that a spatially uniform UVB is a poor approximation and that metal absorption is not sensitive to the epoch when H II regions overlap globally even at column densities of 1012 cm-2. We find, consistent with observations, that the C II mass fraction drops to low redshift while C IV rises owing the combined effects of a growing UVB and continued addition of carbon in low-density regions. This is mimicked in absorption statistics, which broadly agree with observations at z = 6-3 while predicting that the absorber column density distributions rise steeply to the lowest observable columns. Our model reproduces the large observed scatter in the number of low-ionization absorbers per sightline, implying that the scatter does not indicate a partially neutral Universe at z ˜ 6.
Original languageEnglish
Pages (from-to)2526-2539
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - 29 Jul 2015

Keywords / Materials (for Non-textual outputs)

  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift
  • intergalactic medium
  • quasars: absorption lines
  • cosmology: theory


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