Origin of the cold H I gas in Shell-91

Determine whether the cold H I gas within the boundaries of H I Shell-91 formed through stellar-feedback-driven shell expansion or pre-existed before the expansion.

Background

Cold H I clumps are observed both within Shell-91 and outside its apparent boundaries, where some appear to trace the larger-scale MB-Loop I structure. This morphology suggests that at least part of the cold gas may have existed before the shell expanded, while other material may have condensed as a result of feedback. The observations do not resolve the relative origins of these cold-gas components.

References

In addition, the origin of the cold H i gas within shell boundaries remains uncertain.

— A Detailed GASKAP-HI View of Shells and Loops in the Magellanic Bridge  (2609.18160 - Kim et al., 16 Sep 2026) in Section “Discussion,” subsection “Small-scale: cold gas within Shell-91”