A Power Spectrum Description of Galactic Neutral Hydrogen

Abstract

Angular power spectra for neutral hydrogen towards l = 140°, b ≈ 0° on scales from ≈ 1° to ${{\tfrac{1}{{10}}}^{ \circ }}$ are presented. The spectra are generally well fitted by a power-law dependence on radius in the uv-plane, with an index between ≈-2.2 and ≈ -3.0. The more distant hydrogen, which corresponds to larger physical scales, tends to have a more negative index than does the nearer material. There is no preferred angular scale apparent at any velocity. For the distant hydrogen there is no obvious difference between the slope of power spectra for emission aligned perpendicular compared with that parallel to the Galactic plane.