Galactic Spiral Pattern beyond the Optical Size Induced by the Triaxial Dark Halo

[摘要] We suggest a possible mechanism for the formation of non-tidal gaseous structures in galactic outskirts. According to recent observations, extended spiral structures are detected beyond the optical radii R opt in numerous disk galaxies. Such features can be clearly seen in deep HI and UV images (e.g., NGC 3198, NGC 3359, NGC 2841, NGC 3198). We argue, based on our gas-dynamical simulations, that such outer spirals could form as a result of the interaction of the galactic disk with the triaxial host dark matter halo.

[关键词] galaxies kinematics and dynamics;galaxies spiral;galaxies structure