%0 Journal Article
%T The clustering properties of the Lyman-alpha clouds
%A S. Cristiani
%A S. D'Odorico
%A V. D'Odorico
%A A. Fontana
%A E. Giallongo
%A S. Savaglio
%J Physics
%D 1996
%I arXiv
%R 10.1093/mnras/285.1.209
%X We analyze the clustering properties of a high-resolution (~10 km/s) sample of about 1600 Lyman-alpha lines in the spectra of 15 quasars, obtained in the framework of an ESO key-programme with the addition of literature data. The two-point correlation function in the velocity space shows a significant signal on small velocity scales (Delta v < 300 km/s) with amplitude and significance increasing with increasing column density. The correlation scale at z~3 turns out to be 200 - 300 h_{50}^{-1} kpc. A trend of increasing correlation with decreasing redshift is apparent. The existence of over- and under-densities on scales of a few tens of Megaparsec is confirmed with a high confidence level and a number of possible structures are identified. The present observations are found to be consistent with models of gravitationally induced correlations. A continuity scenario between Lyman-alpha and metal systems emerges, with a suggested physical association between the Lyman-$\alpha$ clouds with log N_{HI} > 14 and the halos of protogalactic systems.
%U http://arxiv.org/abs/astro-ph/9610006v1