The Reionization of Carbon

Abstract

Observations suggest that CII was more abundant than CIV in the intergalactic medium towards the end of the hydrogen reionization epoch. This transition provides a unique opportunity to study the enrichment history of intergalactic gas and the growth of the ionizing background (UVB) at early times. We study how carbon absorption evolves from z=10-5 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 that of Haardt & Madau (2012), which is fair agreement given the uncertainties. Nonetheless, we use a calibration in post-processing to account for Lyman-alpha 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 densites 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=6.

16 pages, 14 figures, accepted to MNRAS

References in corpus (9)

• Cosmological Simulations of Intergalactic Medium Enrichment from Galactic Outflows
• Mass, Metal, and Energy Feedback in Cosmological Simulations
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• Radiative recombination data for modelling dynamic finite-density plasmas
• A downturn in intergalactic CIV as redshift 6 is approached
• Intergalactic CIV absorption at redshifts 5.4 to 6
• Large-scale environment of z~5.7 CIV absorption systems I: projected distribution of galaxies
• How to Search for Islands of Neutral Hydrogen in the $z\sim 5.5$ IGM
• Low-mass galaxy formation and the ionizing photon budget during reionization

Cited by in corpus (13)

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• Epoch of Reionisation 21cm Forecasting From MCMC-Constrained Semi-Numerical Models
• The evolution of the Si IV content in the Universe from the epoch of reionization to cosmic noon
• Constraining the reionization history using deep learning from 21cm tomography with the Square Kilometre Array
• The Minimum Halo Mass for Star Formation at z = 6 - 8
• Examining the Decline in the C IV Content of the Universe over 4.3 < z < 6.3 using the E-XQR-30 Sample
• The comoving mass density of MgII from $z\sim 2$ to $5.5$
• Simulated metal and HI absorption lines at the conclusion of Reionization
• Aligned metal absorbers and the ultraviolet background at the end of reionization
• Metal enrichment signatures of the first stars on high-z DLAs
• Probing the Metal Enrichment of the Intergalactic Medium at $z=5-6$ Using the Hubble Space Telescope
• Theoretical study of an LAE-CIV absorption pair at z = 5.7