Metal Lines Associated with the Lyman-alpha Forest from eBOSS Data

Understand

We investigate the metal species associated with the Ly$\alpha$ forest in the eBOSS quasar spectra.

• Metal absorption lines are revealed in the stacked spectra from cross-correlating the selected Ly$\alpha$ absorbers in the forest and the flux fluctuation field.
• Up to 13 metal species are identified associated with relatively strong Ly$\alpha$ absorbers (those with flux fluctuation $-1.0<\delta_{\rm Ly\alpha}<-0.6$ and with neutral hydrogen column density of ~ $10^{15-16}$ $\rm cm^{-2}$) over absorber redshift range of $2<z_{\rm abs}<4$.
• The column densities of these species decrease toward higher redshift and for weaker Ly$\alpha$ absorbers.