The reionization of carbon
2015 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 447, no 3, 2526-2539 p.Article in journal (Refereed) Published
Observations suggest that CII was more abundant than CIV in the intergalactic medium towards the end of the hydrogen reionization epoch (z similar to 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 similar to 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 a 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 HII regions overlap globally even at column densities of 10(12) cm(-2). We find, consistent with observations, that the CII mass fraction drops to low redshift while CIV 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 similar to 6.
Place, publisher, year, edition, pages
2015. Vol. 447, no 3, 2526-2539 p.
galaxies: evolution, galaxies: formation, galaxies: high-redshift, intergalactic medium, quasars: absorption lines, cosmology: theory
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-116523DOI: 10.1093/mnras/stu2668ISI: 000350273200036OAI: oai:DiVA.org:su-116523DiVA: diva2:809470