Strong Clustering in the Low-Redshift Ly alpha Forest

Abstract

The two-point correlation function, ξ, of Lyα forest is found to be large, ξ = 1.8^+1.6^_-1.2_, greater than 90% confidence level, on the scale of 250-500 km s^-1^ for a sample of absorbers (0 < z < 1.3) assembled from Hubble Space Telescope Key Project Observations. This correlation function is stronger than at high redshift (z > 1.7) where ~ ξ ~ 0.2 for velocities greater than 250 km s^-1^.