2000MNRAS.311..657L

The spatial distribution of Lyα forest absorption systems towards 10 QSOs is analysed to search for large-scale structure over the redshift range 2.2<z<3.4. The QSOs form a closely spaced group on the sky and are concentrated within a 1-deg² field. We employ a technique based on the first and second moments of the transmission probability density function which is capable of identifying and assessing the significance of regions of over- or underdense Lyα absorption. We find evidence for large-scale structure in the distribution of Lyα forest absorption at the >99per cent confidence level. In individual spectra we find overdense Lyα absorption on scales of up to 1200km.s^–1. There is also strong evidence for correlated absorption across line-of-sight pairs separated by <3h^–1 proper Mpc (q₀=0.5). For larger separations the cross-correlation signal becomes progressively less significant.