DYNAMICAL HISTORY OF LY-ALPHA CLOUDS

The clustering properties of Ly alpha lines are analyzed using interme diate-resolution (similar to 1 Angstrom) spectra of 67 QSOs compiled f rom the literature. The pair velocity correlation function indicates a weak excess in velocity intervals up to 600 km s(-1). The z-integrate d probability distribution of interline spacings confirms the excess i n the low velocity intervals. The dependence of pair velocity correlat ion on redshift and equivalent width are investigated. The cross-corre lation properties of Ly alpha clouds with metal-line redshifts are ana lyzed. No tendency of Ly alpha lines to cluster around metal-line syst ems is found. Dependence of the cross-correlation on redshift and equi valent width of Ly alpha clouds is investigated. Various implications of the results are discussed.