Determine the physical origin of the EON protrusion

Determine whether the approximately 4 pc-long EON protrusion is produced by hot-gas outflow and stellar feedback from the extended Orion nebula shell or is instead a pre-existing density structure in the surrounding interstellar medium.

Background

The H I observations reveal an elongated structure extending roughly 4 pc from the EON shell. Its morphology and kinematics suggest that it may be associated with gas escaping from the shell, but its lack of a clear velocity gradient, low dust temperature, and extension beyond the [C II] structure also support an interpretation as pre-existing material.

The authors do not resolve whether the protrusion is generated by stellar feedback or is an unrelated or pre-existing structure. The conclusions explicitly retain both possibilities.