Spatial variations of turbulent properties of neutral hydrogen gas in the Small Magellanic Cloud using structure function analysis

TL;DR

This study analyzes the turbulence of neutral hydrogen in the Small Magellanic Cloud, finding homogeneous turbulent properties across regions and suggesting large-scale gravitational effects dominate over stellar feedback.

Contribution

It provides the first detailed structure function analysis of HI turbulence in the SMC, challenging the role of stellar feedback in turbulence variation.

Findings

No significant difference in turbulence between central and outer regions.

Turbulent properties are homogeneous across the SMC at 30 pc resolution.

Large-scale gravitational driving likely influences HI turbulence more than stellar feedback.

Abstract

We investigate spatial variations of turbulent properties in the Small Magellanic Cloud (SMC) by using neutral hydrogen HI observations. With the goal of testing the importance of stellar feedback on HI turbulence, we define central and outer SMC regions based on the star formation rate (SFR) surface density, as well as the HI integrated intensity. We use the structure function and the Velocity Channel Analysis (VCA) to calculate the power-law index (gamma) for both underlying density and velocity fields in these regions. In all cases, our results show essentially no difference in gamma between the central and outer regions. This suggests that HI turbulent properties are surprisingly homogeneous across the SMC when probed at a resolution of 30 pc. Contrary to recent suggestions from numerical simulations, we do not find a significant change in gamma due to stellar feedback as traced by the SFR surface density. This could be due to the stellar feedback being widespread over the whole of the SMC, but more likely due to a large-scale gravitational driving of turbulence. We show that the lack of difference between central and outer SMC regions can not be explained by the high optical depth HI.