Large-scale structure in the Lyman-alpha forest II: analysis of a group of ten QSOs
Abstract
The spatial distribution of Ly-alpha forest absorption systems towards ten QSOs has been 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 have employed 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 Ly-alpha absorption. We find evidence for large-scale structure in the distribution of Ly-alpha forest absorption at the > 99 per cent confidence level. In individual spectra we find overdense Ly-alpha absorption on scales of up to 1200 km s-1. There is also strong evidence for correlated absorption across line of sight pairs separated by < 3 h-1 proper Mpc (q0 = 0.5). For larger separations the cross-correlation signal becomes progressively less significant.
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