Jc. Charlton et al., COMPETITION BETWEEN PRESSURE AND GRAVITY CONFINEMENT IN LY-ALPHA FOREST OBSERVATIONS, The Astrophysical journal, 430(1), 1994, pp. 120000029-120000032
A break in the distribution function of Lyalpha clouds (at a typical r
edshift of 2.5) has been reported by Petit-jean et al. (1993). This fe
ature is what would be expected from a transition between pressure con
finement and gravity confinement (as predicted in Charlton, Salpeter,
& Hogan 1993). The column density at which the feature occurs has been
used to determine the external confining pressure, approximately 10 c
m-3 K, which could be due to a hot, intergalactic medium. For models t
hat provide a good fit to the data, the contribution of the gas in clo
uds to OMEGA is small. The specific shape of the distribution function
at the transition (predicted by models to have a nonmonotonic slope)
can serve as a diagnostic of the distribution of dark matter around Ly
alpha forest clouds, and the present data already eliminate certain mo
dels.