| Abstract : | In the present work we have analysed the effect of the dark haloes on the orbital and escape dynamics of stars in barred galaxies. For that, a 3D gravitational model composed by central nucleus, strong bar, disc and dark halo has been developed and then studied from the point of view of escape phenomena in an open Hamiltonian system. In addition this model is further investigated for the following dark halo profiles viz. oblate and NFW. Then the nature of the stellar orbits is visualized in the plane of the bar. Further Poincaré surface section maps in both the x - y and x - p_x (p_x is the momentum along x - direction) planes for different escape energy values have been plotted to visualise the chaotic and regular domains of motion. Finally the variation of chaos with the mass, size, circular velocity and the nature of the dark haloes via the maximal Lyapunov exponent values has been investigated. We found that oblate dark haloes along with strong bars are preferred to justify the formations of full-fledged spiral arms and extended dark matter distributions in the giant spiral galaxies than the NFW dark haloes, only if they host central SMBHs. Again, in the absence of central SMBHs, the same dark halo and bar combination well justify the formations of less prominent spiral arms and dark matter dominated cores in the dwarf and LSB galaxies. Further for the NFW dark haloes along with strong bars more central violences or chaotic stellar feedbacks are required to form escaping stellar patterns in form of spiral arms. The NFW dark haloes are found preferred for the galaxies with highly energetic massive centres than usual barred galaxies and existence of double stellar bars may invoke such enormous energies in the centres. |
