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SUMMARY:The origin and nature of spiral features in galactic disks - Sharo
 n Meidt van der Wel Ghent University
DTSTART:20241107T160000Z
DTEND:20241107T170000Z
UID:TALK223804@talks.cam.ac.uk
CONTACT:Jan Scholtz
DESCRIPTION:In this talk I will discuss a new view of structure formation 
 in galactic disks mediated by gravity and rotation in the regime beyond wh
 ere the Toomre criterion applies.  The description is an extension of the 
 Lin-Shu framework to the regime of 'open spiral’ waves\, well outside th
 e conventional 'tight-winding' limit.  In this regime\, structures grow re
 adily but at specific `critical’ orientations (pitch angles) that help\,
  given local conditions\, the growing wave capitalize on azimuthal gravita
 tional forcing.  From this perspective the ‘swing amplification’ of sh
 earing material patterns results from the spiral pattern’s swing through
  the critical pitch angle.  The same physical process also stimulates the 
 growth of wave modes at corotation.   In both cases\, the spiral structure
 s that go on to dominate a disk's appearance are predicted to appear on sc
 ales nearer to the Jeans length than the Toomre length.  In gas disks\, th
 is makes them consistent with the highly regular\, remarkably long filamen
 tary features newly revealed by JWST across the neutral gas disks of nearb
 y galaxies. 
LOCATION:Hoyle Lecture Theatre\, Institute of Astronomy
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