Interaction between collisionless galactic discs and non-axisymmetric dark matter haloes

Abstract

Using N -body simulations (N ∼ 10 6 − 10 7 ), we examine how a non-axisymmetric dark halo affects the dynamical evolution of the structure in collisionless (stellar) discs. We demonstrate how the model parameters such as mass of the halo, initial conditions in the disc and the halo axes ratio affect morphology and kinematics of the stellar discs. We show that a non-axisymmetric halo can generate a large-scale spiral density pattern in the embedded stellar disc. The pattern is observed in the disc for many periods of its revolution, even if the disc is gravitationally over-stable. The growth of the spiral arms is not accompanied by significant dynamical heating of the disc, irrelevant to its initial parameters. We also investigate transformation of the dark halo's shape driven by the long-lived spiral pattern in the disc . We show that the analysis of the velocity field in the stellar disc and in the spiral pattern gives us a possibility to figure out the spatial orientation of the triaxial-shaped dark halo and to measure the triaxiality.

Dark matter in galaxies

“…Of special interest is the possibility to explain the appearance and support of a regular spiral structure of galaxies due to the disk interplay with a non-axially symmetric halo. Numerical simulations clearly showed how non-axially symmetric gravitational potential of a massive halo in the disk plain leads to the formation of two-arms spiral pattern in the gaseous [164] and stellar [165]. disks.…”

“…But, despite indirect evidences for triaxial density distribution in halos, its form and ellipticity for individual galaxies have been poorly known so far, and moreover sometimes estimates of halo form are contradictory. Some papers, for example [164][165][166][167][168][169][170], studied different aspects of the effect of a non-axially symmetric gravitational potential on the dynamics of galactic disks. In particular, it was noted that the triaxia halo form complicates interpretation of the galaxy rotation curve and velocity field, especially if the dark halo dominates even in the inner galaxy (for example, in low surface brightness galaxies) [169,171].…”

“…The lack of central symmetry in dark matter distribution, prolateness or triaxiality of halo discussed in Section 5, pose question on the influence of such features on the galactic disk dynamics [166,266,267]. Different aspects of the non-axial symmetry of gravitational potential on the disk dynamics were considered in papers [164,165,169,170,268]. The halo triaxiality was invoked to explain gas velocity field in galaxies, in particular, in LSB-galaxies [169,171].…”

New Features of Parallel Implementation of N-Body Problems on GPU

“…, V c is the circular velocity in the disk equatorial plane (z = 0). In Eqs (1), (2) we neglect the gravitational interaction between dark matter halo, stellar bulge and gaseous component [9,16,17]. According to this model iterative procedure of the disk initial conditions generation is described in Ref.…”

Dark matter in galaxies

“…²ÂÊÎËÚÐÞÏ ÂÔÒÇÍÕÂÏ ÄÎËâÐËâ ÐÇÑÔÇÔËÏ-ÏÇÕÓËÚÐÑÔÕË ÅÓÂÄËÕÂÙËÑÐÐÑÅÑ ÒÑÕÇÐÙËÂΠРAEËÐÂÏËÍÖ AEËÔÍ ÒÑÔÄâÜÇÐÞ ÓÂÃÑÕÞ [172,173,177,178,276].…”