Length-scales and Dynamics of Carina's Western Wall

TL;DR

This study analyzes the turbulent dynamics of the Carina Nebula's Western Wall PDR using high-resolution ALMA data, revealing large-scale turbulence driven by shocks and identifying key length-scales influenced by gravity and turbulence interplay.

Contribution

It provides new insights into the turbulence driving mechanisms and length-scales in a PDR, highlighting the role of shocks and the interplay between gravity and turbulence.

Findings

Turbulence is driven at large scales.

Shocks dominate the turbulence structure.

Length-scales of 0.02-0.03 pc are significant.

Abstract

We present a variety of analyses of the turbulent dynamics of the boundary of a photo-dissociation region (PDR) in the Carina Nebula using high resolution ALMA observations. Using Principal Component Analysis we suggest that the turbulence in this molecular cloud is driven at large scales. Analysis of the centroid velocity structure functions indicate that the turbulence is dominated by shocks rather than local (in k-space) transport of energy. We further find that length-scales in the range 0.02 - 0.03 pc are important in the dynamics of this cloud and this finding is supported by analysis of the dominant emission structure length-scale. These length-scales are well resolved by the observational data and we conclude that the apparent importance of this range of scales is physical in origin. Given that it is also well within the range strongly influenced by ambipolar diffusion, we conclude that it is not primarily a product of turbulence alone, but is more likely to be a result of the interplay between gravity and turbulence. Finally, through comparison of these results with previous observations of H2 emission from the Western Wall we demonstrate that observations of a PDR can be used to probe the internal structure of the undisturbed portion of a molecular cloud.