Cross-correlation of the Lyα and C iv forests as a probe of the intergalactic medium enrichment

The enrichment of the intergalactic medium (IGM) provides important information about the history of galaxy formation and evolution, because the amount, extent, and distribution of metals in the IGM are related to the star formation history and outflow mechanisms of galaxies. Traditional approaches that rely on the detection of discrete absorption lines are challenging to implement at high redshifts (z ≳ 5) due to the worsening detector sensitivity combined with increasing sky background in the NIR, resulting in low signal-to-noise spectra. Using mock skewers drawn from the Nyx simulations, we present the cross-correlation between the Lyα and C iv forests as a probe to constrain the enrichment topology and metallicity of the IGM. We simulate the IGM at z = 4.5 using the Nyx hydrodynamical simulation and model IGM enrichment by assuming that certain massive halos enrich the gas to some radius. We compute the two-point cross-correlation between the Lyα and C iv forests and investigate its dependence on model parameters. Using mock datasets consisting of 25 quasars with SNR/pixel of 50 at z = 4.5, we show that cross-correlation can effectively constrain the minimum halo mass log(M), the enrichment radius R, and the metallicity [C/H]. Moreover, the combination of the auto-correlation of the C iv forests and the cross-correlation between the Lyα and C iv forests substantially improves the precision of these constraints, with ≳ 2 × improvements in measurement precision.