HI and metal absorption lines during the Epoch of Reionization

In this work, we study the epoch of Reionization (EoR) with metal absorption lines in quasar spectra at high redshift, using high resolution hydrodynamical simulations (an improved version of GADGET-3). For this purpose, we set up the physical conditions of the intergalactic medium (IGM) at the redshift of the EoR, and we post-process the simulations to implement a uniform UV ionizing background for quasars and galaxies (Haardt-Madau 2012), the metal ions with CLOUDY 8.1 and HI self-shielding prescription (Rahmati et al. 2013). We use Voigt profile fitting to compute the column densities of the ions from the synthetic spectra and obtain a statistical distribution of the absorbers. This procedure allows us to study the evolution of the state of the IGM at high redshift, compute the cosmological mass density of CIV and HI and other ions. Our simulations produce absorbers properties that are in good agreement with observations in the literature, especially for the high ionization species.

Furthermore, we are able to reproduce an observed example of an LAE galaxy-CIV absorber pair at z=5.7, proving a physical insight into such systems beyond the limit of current observations. Finally, we vary of the uniform UVB at z~6, and compare directly with observations of different metal ions, in order to constrain the ionizing background at the tail of Reionization.