Orbital dynamics of three-dimensional bars: II. Investigation of the parameter space

Academy of Athens, Athínai, Attica, Greece
Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.11). 07/2002; DOI: 10.1046/j.1365-8711.2002.05469.x
Source: arXiv

ABSTRACT We investigate the orbital structure in a class of 3D models of barred galaxies. We consider different values of the pattern speed, of the strength of the bar and of the parameters of the central bulge of the galactic model. The morphology of the stable orbits in the bar region is associated with the degree of folding of the x1-characteristic. This folding is larger for lower values of the pattern speed. The elongation of rectangular-like orbits belonging to x1 and to x1-originated families depends mainly on the pattern speed. The detailed investigation of the trees of bifurcating families in the various models shows that major building blocks of 3D bars can be supplied by families initially introduced as unstable in the system, but becoming stable at another energy interval. In some models without radial and vertical 2:1 resonances we find, except for the x1 and x1-originated families, also families related to the z-axis orbits, which support the bar. Bifurcations of the x2 family can build a secondary 3D bar along the minor axis of the main bar. This is favoured in the slow rotating bar case. Comment: 11 pages, 20 figures, 1 table, to appear in MNRAS

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Available from: Charalampos Skokos, Aug 05, 2013
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    • "Hamiltonian systems or symplectic mappings), in which new and more complicated phenomena are expected in higher dimensions. Hamiltonian systems with n≥2 degrees of freedom have been studied extensively in the context of celestial mechanics, especially with regard to problems of galactic dynamics [1] [2] [3] [4] [5] . "
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    ABSTRACT: In this paper, we first present numerical methods that allow us to compute accurately periodic orbits in high dimensional mappings and demonstrate the effectiveness of our methods by computing orbits of various stability types. We then use a terminology for the different stability types, which is perfectly suited for systems with many degrees of freedom, since it clearly reflects the configuration of the eigenvalues of the corresponding monodromy matrix on the complex plane. Studying the distribution of these eigenvalues over the points of an unstable periodic orbit, we attempt to find connections between local dynamics and the global morphology of the orbit.
    " Proceedings of the 4th GRACM Congress on Computational Mechanics", ed. Tsahalis D. T.; 01/2002
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    ABSTRACT: In this series of papers we investigate the orbital structure of 3D models representing barred galaxies. In the present introductory paper we use a fiducial case to describe all families of periodic orbits that may play a role in the morphology of three-dimensional bars. We show that, in a 3D bar, the backbone of the orbital structure is not just the x1 family, as in 2D models, but a tree of 2D and 3D families bifurcating from x1. Besides the main tree we have also found another group of families of lesser importance around the radial 3:1 resonance. The families of this group bifurcate from x1 and influence the dynamics of the system only locally. We also find that 3D orbits elongated along the bar minor axis can be formed by bifurcations of the planar x2 family. They can support 3D bar-like structures along the minor axis of the main bar. Banana-like orbits around the stable Lagrangian points build a forest of 2D and 3D families as well. The importance of the 3D x1-tree families at the outer parts of the bar depends critically on whether they are introduced in the system as bifurcations in $z$ or in $\dot{z}$. Comment: 16 pages, 22 figures, 3 tables, to appear in MNRAS
    Monthly Notices of the Royal Astronomical Society 07/2002; DOI:10.1046/j.1365-8711.2002.05468.x · 5.11 Impact Factor
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    ABSTRACT: Boxy edge-on profiles can be accounted for not only in models of barred galaxies, but also in models of normal (non-barred) galaxies. Thus, the presence of a bar is not a sine qua non condition for the appearance of this feature, as often assumed. We show that a `boxy' or a `peanut' structure in the central parts of a model is due to the presence of vertical resonances at which stable families of periodic orbits bifurcate from the planar x1 family. The orbits of these families reach in their projections on the equatorial plane a maximum distance from the center, beyond which they increase their mean radii by increasing only their deviations from the equatorial plane. The resulting orbital profiles are `stair-type' and constitute the backbone for the observed boxy structures in edge-on views of $N$-body models and, we believe, in edge-on views of disc galaxies. Since the existence of vertical resonances is independent of barred or spiral perturbations in the disc, `boxy' profiles may appear also in almost axisymmetric cases. Comment: 5 pages, 4 figures, to appear in MNRAS
    Monthly Notices of the Royal Astronomical Society 10/2002; DOI:10.1046/j.1365-8711.2002.05686.x · 5.11 Impact Factor
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