The SEDIGISM survey: Molecular cloud morphology

Abstract

The Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium (SEDIGISM) survey has produced high (spatial and spectral) resolution 13CO (2−1) maps of the Milky Way. It has allowed us to investigate the molecular interstellar medium in the inner Galaxy at an unprecedented level of detail and characterise it into molecular clouds (MCs). In a previous paper, we classified the SEDIGISM clouds into four morphologies. However, how the properties of the clouds vary for these four morphologies is not well understood. Here, we use the morphological classification of SEDIGISM clouds to find connections between the cloud morphologies, their integrated properties, and their location on scaling relation diagrams. We observe that ring-like clouds show the most peculiar properties, having, on average, higher masses, sizes, aspect ratios, and velocity dispersions, compared to other morphologies. We speculate that this is related to the physical mechanisms that regulate their formation and evolution; for example, turbulence from stellar feedback can often result in the creation of bubble-like structures. We also see a trend of morphology with the virial parameter, whereby ring-like, elongated, clumpy, and concentrated clouds have virial parameters in decreasing order. Our findings provide a foundation for a better understanding of MC behaviour, based on their measurable properties.