Chaos in elliptical galaxies
Abstract
We investigated stellar orbits in a self--consistent and strongly triaxial model elliptical galaxy obtained from a cold collapse. We obtained the six Lyapunov characteristic exponents for 596 orbits and we found that for 39% of the orbits the two largest exponents have positive values, while for 17% of them only the largest exponent has a positive value. We dubbed the former fully chaotic orbits and the latter partially chaotic orbits, a distinction to which not much importance has been given thus far, as all orbits with at least one positive exponent are usually regarded as chaotic. Nevertheless, we found that partially chaotic orbits have a distribution similar to the one of regular orbits and not to that of the fully chaotic ones. That is, fully chaotic orbits contribute to the more spherical component of the galaxy, while partially chaotic and regular orbits are together responsible for the triaxial form. This result is reasonable, because partially chaotic orbits obey a second integral, or pseudo integral, besides the energy (or, alternatively, they fulfil a resonance relationship). In brief, all the Lyapunov exponents (and not just the largest one) should be computed and partially and fully chaotic orbits should be distinguished in dynamical studies of stellar systems.
- Publication:
-
Boletin de la Asociacion Argentina de Astronomia La Plata Argentina
- Pub Date:
- 2002
- Bibcode:
- 2002BAAA...45...69M