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Astron. Astrophys. 334, 829-839 (1998)

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Vertical orbital structure around the Lagrangian points in barred galaxies

Link with the secular evolution of galaxies

Mercè Ollé 1, 2 and Daniel Pfenniger 1

1 Geneva Observatory, CH-1290 Sauverny, Switzerland
2 ETSEIB, Departament Matemàtica Aplica I, Diagonal 647, Barcelona, Spain

Received 21 August 1997 / Accepted 19 March 1998

Abstract

The stability of the Lagrangian points and the vertical periodic orbits around them is examined in the context of barred galaxies. A transition from stability to complex instability appears for the points [FORMULA] and [FORMULA] when the strength of the bar is sufficiently large. The Hopf-like bifurcation associated to such a transition is inverse and its effects on the central family of periodic orbits and neighbouring orbits are described. This instability can play an important role for barred galaxies secularly increasing the strength of their bar, because a sudden full destabilization of matter around these Lagrangian points must occur. This effect is demonstrated with a sample of trajectories diffusing away from the corotation circle several [FORMULA] radially, and several kpc out the galaxy plane.

Key words: celestial mechanics, stellar dynamics – galaxies: evolution – galaxies: kinematics and dynamics – galaxies: spiral – galaxies: structure

Send offprint requests to: Daniel.Pfenniger@obs.unige.ch

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© European Southern Observatory (ESO) 1998

Online publication: June 2, 1998

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