FORMATION OF INTERMEDIATE-SCALE STRUCTURES IN SPIRAL GALAXIES

다국어 초록 (Multilingual Abstract)

Disk galaxies abound with intermediate-scale structures such as OB star complexes, giant clouds, anddust spurs in a close geometrical association with spiral arms. Various mechanisms have been proposedas candidates for their origin, but a comprehensive theory should encompass fundamental physical agentssuch as self-gravity, magnetic elds, galactic dierential rotation, and spiral arms, all of which are knownto exist in disk galaxies. Recent numerical simulations incorporating all these physical processes showthat magneto-Jeans instability (MJI), in which magnetic tension resists the stabilizing Coriolis force ofgalaxy rotation, is much more powerful than swing-amplication or the Parker instability in forming self-gravitating intermediate-scale structures. The MJI occurring in shearing and expanding ows o spiralarms rapidly forms structures elongated along the direction perpendicular to the arms, remarkablysimilar to dust spurs seen inHST images of spiral galaxies. In highly nonlinear stages, these spursfragment to form bound clumps, possibly evolving into bright arm and interarm HI regions, suggestingthat all these intermediate-scale structures in spiral galaxies probably share a common dynamical origin.

참고문헌 (Reference)

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