http://arxiv.org/abs/1809.05813
We present further results of a survey for absorption line systems in the spectra of four high redshift quasars (5.79 $\le$ z${\textrm{em}}$ $\le$ 6.13) obtained with the ESO Very Large Telescope X-Shooter. We identify 36 $\textrm{CIV}$ and 7 $\textrm{SiIV}$ systems with a $\ge$ 5$\sigma$ significance. The highest redshift $\textrm{CIV}$ and $\textrm{SiIV}$ absorbers identified in this work are at z = 5.80738 $\pm$ 0.00017 and z = 5.77495 $\pm$ 0.00038, respectively. We compute the comoving mass density of $\textrm{SiIV}$ ($\Omega{\textrm{SiIV}}$) and find that it evolves from $\Omega_{\textrm{SiIV}}$ = 4.3$^{+2.1}{-2.1}$ $\times$10$^{-9}$ at <z> = 5.05 to $\Omega{\textrm{SiIV}}$ = 1.4$^{+0.6}{-0.4}$ $\times$10$^{-9}$ at <z> = 5.66. We also measure $\Omega{\textrm{CIV}}$ = 1.6$^{+0.4}{-0.1}$ $\times$10$^{-8}$ at <z> = 4.77 and $\Omega{\textrm{CIV}}$ = 3.4$^{+1.6}{-1.1}$ $\times$10$^{-9}$ at <z> = 5.66. We classify our $\textrm{CIV}$ absorber population by the presence of associated $\textit{low}$ and/or $\textit{high ionisation}$ systems and compute their velocity width ($\Delta$v${90}$). We find that all $\textrm{CIV}$ systems with $\Delta$v$_{90}$ > 200 kms$^{-1}$ have associated $\textit{low ionisation}$ systems. We investigate two such systems, separated by 550 physical kpc along a line of sight, and find it likely that they are both tracing a multi-phase medium where hot and cold gas is mixing at the interface between the CGM and IGM. We further discuss the \textrm{MgII} systems presented in a previous work and we identify 5 $\textrm{SiII}$, 10 $\textrm{AlII}$, 12 $\textrm{FeII}$, 1 $\textrm{CII}$, 7 $\textrm{MgI}$ and 1 $\textrm{CaII}$ associated transitions. We compute the respective comoving mass densities in the redshift range 2 to 6, as allowed by the wavelength coverage.
A. Codoreanu, E. Ryan-Weber, L. García, et. al.
Tue, 18 Sep 18
51/70
Comments: Accepted for publication in MNRAS 22 pages, 19 figures, 6 tables
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