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

TL;DR

This study uses numerical simulations to analyze how turbulent velocity influences the ext{HI} intensity fluctuation power spectrum in spiral galaxies, revealing different dependencies based on emission velocity range.

Contribution

It demonstrates that the ext{HI} intensity fluctuation spectrum depends on either column density or turbulent velocity, depending on the velocity range considered, clarifying observational interpretations.

Findings

Intensity fluctuation depends on column density spectrum when all emission is considered.

Fluctuation depends on turbulent velocity when emission is limited to smaller velocity ranges.

Results have implications for interpreting ext{HI} fluctuation observations in 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.