Effect of turbulent velocity on the HI intensity fluctuation power spectrum from spiral galaxies

Abstract

We use numerical simulations to investigate effect of turbulent velocity on the power spectrum of HI intensity from external galaxies when (a) all emission is considered, (b) emission with velocity range smaller than the turbulent velocity dispersion is considered. We found that for case (a) the intensity fluctuation depends directly only on the power spectrum of the column density, whereas for case (b) it depends only on the turbulent velocity fluctuation. We discuss the implications of this result in real observations of HI fluctuations.