Revealing the Character of Orbits in a Binary System Consisting of a Primary Galaxy and a Satellite Companion
Abstract
In this article, we present a galactic gravitational model of three degrees of freedom (3D), in order to study and reveal the character of the orbits of the stars, in a binary stellar system composed of a primary quiet or active galaxy and a small satellite companion galaxy. Our main dynamical analysis will be focused on the behaviour of the primary galaxy. We investigate in detail the regular or chaotic nature of motion, in two different cases: (i) the timeindependent model in both 2D and 3D dynamical systems and (ii) the timeevolving 3D model. For the description of the structure of the 2D system, we use the classical method of the Poincaré (x, p_{x} ), y = 0, p_{y} < 0 phase plane. In order to study the structure of the phase space of the 3D system, we take sections in the plane y = 0 of the 3D orbits, whose initial conditions differ from the plane parent periodic orbits, only by the z component. The set of the fourdimensional points in the (x, p_{x} , z, p_{z} ) phase space is projected on the (z, p_{z} ) plane. The maximum Lyapunov characteristic exponent is used in order to make an estimation of the chaoticity of our galactic system, in both 2D and 3D dynamical models. Our numerical calculations indicate that the percentage of the chaotic orbits increases when the primary galaxy has a dense and massive nucleus. The presence of the dense galactic core also increases the stellar velocities near the center of the galaxy. Moreover, for small values of the distance R between the two bodies, lowenergy stars display chaotic motion, near the central region of the galaxy, while for larger values of the distance R, the motion in active galaxies is entirely regular for lowenergy stars. Our simulations suggest that in galaxies with a satellite companion, the chaotic nature of motion is not only a result of the galactic interaction between the primary galaxy and its companion, but also a result caused by the presence of the dense nucleus in the core of the primary galaxy. Theoretical arguments are presented in order to support and interpret the numerically derived outcomes. Furthermore, we follow the 3D evolution of the primary galaxy, when mass is transported adiabatically from the disk to the nucleus. Our numerical results are in satisfactory agreement with observational data obtained from the M51type binary stellar systems. A comparison between the present research and similar and earlier work is also made.
 Publication:

Publications of the Astronomical Society of Australia
 Pub Date:
 February 2013
 DOI:
 10.1017/pasa.2012.012
 arXiv:
 arXiv:1303.0881
 Bibcode:
 2013PASA...30...12Z
 Keywords:

 galaxies: interactions;
 galaxies: kinematics and dynamics;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 Published in Publications of the Astronomical Society of Australia (PASA) journal. arXiv admin note: previous paper with related context: arXiv:1204.5204