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Ordered and chaotic spiral arms
Author(s) -
Patsis P.A.
Publication year - 2008
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200811077
Subject(s) - physics , spiral galaxy , chaotic , barred spiral galaxy , spiral (railway) , grand design spiral galaxy , stars , ellipse , bar (unit) , astrophysics , galaxy , azimuth , invariant (physics) , classical mechanics , elliptical galaxy , astronomy , disc galaxy , mathematical physics , mathematical analysis , mathematics , artificial intelligence , meteorology , computer science
The stellar flow at the arms of spiral galaxies is qualitatively different among different morphological types. The stars that reinforce the spiral arms can be either participating in an ordered or in a chaotic flow. Ordered flows are associated with normal (non‐barred) spiral galaxies. Typically they are described with precessing ellipses corresponding to stable periodic orbits at successive energies (Jacobi constants). On the contrary, the spiral arms in barred‐spiral systems may be supported by stars in chaotic motion. The trajectories of these stars are associated with the invariant manifolds of the unstable Lagrangian points ( L 1,2 ). Response and orbital models indicate that this kind of spirals either stop at an azimuth smaller than π /2, or present large gaps at about this angle. Chaotic spirals appear in strong bars having ( L 1,2 ) close to the ends of the bar. The arms of barred‐spiral systems with corotation away from the end of the bar can be either as in the case of normal spirals, or supported by banana‐like orbits surrounding the stable Lagrangian points ( L 4,5 ). We find also models combining ordered and chaotic flows. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)