Constraining IGM enrichment and metallicity with the C IV forest correlation function

The distribution and abundance of metals in the diffuse intergalactic medium (IGM) have implications for galaxy formation and evolution models, and has been argued to be sensitive to the Universe's reionization history. However, reduced sensitivity in the near-IR implies that probing IGM metals at z > 4 is currently out of reach with the traditional method of detecting individual absorbers. We present a new technique based on clustering analysis that enables the detection of these weak IGM absorbers. We investigate the two-point correlation function (2PCF) of the C IV forest as a probe of IGM metallicity and enrichment topology by simulating the z = 4.5 IGM with models of inhomogeneous metal distributions. The 2PCF of the C IV forest demonstrates a clear peak at a characteristic separation corresponding to the doublet separation of the C IV line.The peak amplitude scales quadratically with metallicity, while enrichment topology affects both the shape and amplitude of the 2PCF. For models consistent with the distribution of metals at z similar to 3, we find that we can constrain [C/H] to within 0.2 dex, log M-min to within 0.4 dex, and R to within 15 per cent. We show that CGM absorbers can be reliably identified and masked, thus recovering the underlying IGM signal. The auto-correlation of the metal-line forest presents a compelling avenue to constrain the IGM metallicity and enrichment topology with high precision at z > 4, thereby pushing such measurements into the Epoch of Reionization.

Automated summary

The distribution and abundance of metals in the diffuse intergalactic medium play a crucial role in galaxy formation and evolution models, and are sensitive to the reionization history of the Universe. A new technique based on clustering analysis allows for the detection of weak absorbers in the intergalactic medium. The two-point correlation function of the C IV forest can be used to probe the metallicity and enrichment topology, providing precise measurements at high redshifts.