The Observed Properties of Lyα Clouds as Signatures of Dark Matter Potential Wells

Abstract

The radial distributions of dark matter (DM) density and temperature in Lyα clouds seen in QSO spectra are discussed in the framework of a ‘minihalo’ model. Available observational data on the distribution of Lyα clouds in column density, in combination with assumptions about the hydrostatic equilibrium of DM and gas, and information provided by the equation of state of the gas, provide a reasonable basis for constraining the shapes of the DM density and temperature distributions. The analysis shows that DM density should be strongly peaked at the cloud center, while DM temperature should have a minimum in this region. In the framework of a minihalo model this work leads to the conjecture that an important process in minihalo formation may be some sort of gravitational-thermal instability in the DM gas.