Supershells in the Multi-Phase Milky Way: Insights from HI Synthesis Imaging and CO Surveys

TL;DR

This study uses high-resolution HI and CO data to analyze the complex multi-phase structure of Galactic supershells, revealing detailed substructures and exploring their formation mechanisms.

Contribution

It provides new parsec-scale observations of supershell walls, highlighting the role of interactions and in-situ formation in creating observed substructures.

Findings

Detection of dense-tipped fingers and molecular clouds in shell walls

Evidence supporting both cloud interaction and in-situ formation processes

Identification of potential instabilities influencing structure evolution

Abstract

We present new parsec-scale resolution data from a multi-phase study of the ISM in the walls of Galactic supershells. HI synthesis images and CO survey data reveal a wealth of substructure, including dense-tipped fingers and extended molecular clouds embedded in shell walls. We briefly consider formation scenarios for these features, and suggest that both the interaction of an expanding shell with pre-existing dense clouds, as well as in-situ formation of CNM and molecular gas, are likely to be relevant. Future work will also examine the role of instabilities in structure formation and breakup, and will investigate the presence of high-altitude gas associated with supershells and chimneys.