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URN: urn:nbn:de:bsz:16-opus-6322
URL: http://www.ub.uni-heidelberg.de/archiv/632
Hinweis zum Urheberrecht.
A new approach to the problem of modes in mestel disks
Über einen neuen Zugang zum Problem von Moden in Mestelscheiben
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Dokument 1.ps (16.432 KB)
SWD-Schlagwörter:
Stellardynamik, Spiralnebel
Freie Schlagwörter (Deutsch):
Scheibengalaxien, Mestelscheibe, Spiralstruktur
Freie Schlagwörter (Englisch):
stellar dynamics, mestel disk, disk galaxies, spiral structure
PACS - Klassifikation:
98.62.Hr
Institut:
ZAH: Astronomisches Rechen-Institut
Fakultät:
Fakultät für Physik und Astronomie
DDC-Sachgruppe:
Physik
Dokumentart:
Dissertation
Hauptberichter:
Fuchs, Burkhard (Prof. Dr.)
Sprache:
Englisch
Tag der mündlichen Prüfung:
17.05.2000
Erstellungsjahr:
2000
Publikationsdatum:
14.06.2000
Kurzfassung in Deutsch:
In this work I examine the modes admitted by the Mestel
disk, a disk with a globally flat rotation curve. In contrast to
previous analyses of this problem by Zang (1976) and Read (1997), I
approximate the orbits to obtain almost closed expressions for the
kernel of the integral equation governing the behaviour of the modes.
I investigate the modes admitted by both the self-consistent and a
cut-out Mestel disk, the difference being that in the latter case a
part of the matter in the disk is immobilized. This breaks the
self-similarity and produces a pronouncedly different picture. While
the expressions for the kernel in the self-consistent disk are quite
managable (though still beyond the reach of analytic techniques), the
kernels for cut-out disks tends to rather complicated indeed.
In general, my approximation reproduces the results of the previous
works remarkably well. Due to the sheer size of the terms, examining
the solution behaviour in the approximation does not save computing
time compared to Zang's method at least for the cut-out disks. The
more handy expressions in the self-consistent disk, on the other hand,
allow an intuitive understanding of most of the properties of neutral
(nonrotating, nongrowing) modes there.
Also,
non-axisymmetric modes of finite growth rate and pattern speed
in the self-consistent
disk become almost treatable. I can prove that there are no such
modes above the velocity dispersions at which the neutral modes
appear, and that any modes that exist below these thresholds cannot
possess a bounded Mellin transform. Unfortunately, I still cannot
prove the
existence of such modes.
