Determine when magnetic fields influence interstellar-medium evolution

Determine under which physical conditions and spatial scales magnetic fields significantly influence the structure and evolution of the interstellar medium, support clouds against gravitational contraction, or affect the fragmentation of clouds into gravitationally bound collapsing clumps.

Background

The paper describes competing evidence about the dynamical role of magnetic fields. On galactic scales, magnetic fields may largely be advected by gas motions, while stellar and nuclear feedback can reorganize them; on smaller scales, they may provide support against gravity or affect cloud fragmentation.

The unresolved issue is therefore the physical and spatial transition between magnetic fields that passively follow gas flows and fields that dynamically regulate collapse and fragmentation. Multi-scale polarization, Zeeman, and molecular-line observations with ALMA2040 and complementary facilities are proposed as a way to investigate this transition.