  Absorption lines in the Lyman-alpha forest can be thought of as peaks in
neutral hydrogen density along lines of sight. The column density distribution
(the number density of absorption lines as a function of column density) is
then a statistic of density peaks, which contains information about the
underlying power spectrum. In particular, we show that the slope of the
distribution provides a measure of power on scales smaller than those probed by
studies of present-day large scale structure.

Astrophysics