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OATS-UNI/TS SEMINAR
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Speaker: Elena D'Onghia (Harvard-Center for Astrophys., Cambridge, USA)
Title: Self-Perpetuating Spiral Arms in Disk Galaxies
Date: Wednesday, May 16th, 2012
Time: 11:30
Venue: Villa Bazzoni
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Abstract:
The precise nature of spiral structure in galaxies remains uncertain.
Recent studies suggest that spiral arms result from interactions between
disks and satellite galaxies. Instead, leaving aside the grand bisymmetric
spirals, here we consider the possibility that the multi-armed spiral
features originate from density inhomogeneities orbiting within disks.
Using high-resolution N-body simulations, we follow the motions of stars
under the influence of gravity, and show that mass concentrations with
properties similar to those of giant molecular clouds can induce the
development of spiral arms through a process termed swing amplification.
However, unlike in earlier work, we demonstrate that the eventual response
of the disk can be highly non-linear, significantly modifying the
formation and longevity of the resulting patterns. Contrary to
expectations, ragged spiral structures can survive at least in a
statistical sense long after the original perturbing influence has been
removed. Our findings thus motivate a new interpretation of many
phenomena, including disk heating, radial migration, and galaxy pattern
speeds.
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Contact: Marisa Girardi (DAUT)