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Astron. Astrophys. 352, 469-478 (1999)


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Resonances and the morphology of spirals in N-body simulations

P.A. Patsis 1,2 and D.E. Kaufmann 3

1 Research Center for Astronomy, Academy of Athens, 14 Anagnostopoulou St., 10673, Athens, Greece
2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
3 Computer Sciences Corporation, 7700 Hubble Drive, Lanham-Seabrook, MD 20706, USA

Received 7 June 1999 / Accepted 11 October 1999

Abstract

We find, by means of N -body simulations, non-linear spiral modes that last from four to seven pattern rotations and secure a grand-design morphology to the models. Their dynamical behavior includes the termination of the strong , symmetric, logarithmic stellar spirals inside their 4:1 resonance radius, as foreseen from the orbital theory and from SPH gasdynamical models. The spiral modes start along the [FORMULA] curve and have weak extensions beyond the 4:1 resonance. Strong, bisymmetric logarithmic spirals end at about 2-3 exponential disk scale lengths. A central oval distortion is always present in the models. In many cases we have more than one dominant mode existing over different distance intervals. For each of these spiral modes we find the regions of resonances as determined by its pattern speed. We observe that the dynamics of the mode are locally influenced by the presence of the resonances.

Key words: galaxies: kinematics and dynamics – galaxies: spiral – galaxies: structure

Send offprint requests to: P.A. Patsis (patsis@mpia-hd.mpg.de)

© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999

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