Off-centred dark matter halo leading to strong central disc lopsidedness

Abstract

There is increasing evidence now from simulations and observations that the centre of dark matter halo in a Milky Way type galaxy could be off-centred by a few 100 pc w.r.t. the galactic disc. We study the effect of such an offset halo on the orbits and kinematics in the central few kpc of the disc. The equations of motion in the disc plane can be written in terms of the disc and halo potentials when these two are concentric and a perturbation term due to the offset halo. This perturbation potential shows an m=1 azimuthal variation, or is lopsided, and its magnitude increases at small radii. On solving these equations, we find that the perturbed orbit shows a large deviation of ~ 40 % in radius at R = 1.5 kpc, and also strong kinematical lopsidedness. Thus even a small halo offset of 350 pc can induce surprisingly strong spatial and kinematical lopsidedness in the central region within ~ 3 kpc radius. Further, the disc would remain lopsided for several Gyr, as long as the halo offset lasts. This would have important implications for the dynamical evolution of this region.

6 pages, 6 figures, Submitted to MNRAS

References in corpus (8)

• The behaviour of dark matter associated with 4 bright cluster galaxies in the 10kpc core of Abell 3827
• Lopsided Spiral Galaxies
• Global lopsided instability in a purely stellar galactic disc
• Spatial and Kinematical Lopsidedness of Atomic Hydrogen in the Ursa Major Group of Galaxies
• Self-consistent massive disks in triaxial dark matter halos
• Measurement of non-axisymmetry in centres of advanced mergers of galaxies
• Angular momentum transport and evolution of lopsided galaxies
• The Galactic Center compared with nuclei of nearby galaxies

Cited by in corpus (2)

• Genesis of morpho-kinematic lopsidedness in minor merger of galaxies
• Identifying lopsidedness in spiral galaxies using a Deep Convolutional Neural Network