2<zobs<4 quasars stacked spectrum

Metal absorption lines are revealed in 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 as being associated with relatively strong Ly{alpha} absorbers (those with flux fluctuations -1.0<{delta}Ly{alpha}<-0.6 and with a neutral hydrogen column density of ~1015^-16^/cm^2^) over the absorber redshift range of 2<zabs<4.

The column densities of these species decrease toward higher redshift and for weaker Ly{alpha} absorbers. From modeling the column densities of various species, we find that the column density pattern suggests contributions from multiple gas components, both in the circumgalactic medium (CGM) and the intergalactic medium (IGM). While the low-ionization species (e.g., C II, Si II, and Mg II) can be explained by high-density, cool gas (T~104 K) from the CGM, the high-ionization species may reside in low-density or high- temperature gas in the IGM.