Asymmetric Warps in Disk Galaxies: Dependence on Dark Matter Halo

The warps in many spiral galaxies are now known to be asymmetric. Recent observations have revealed that asymmetry in warps may be the norm rather than exception. However there exists no generic mechanism to generate these asymmetries in warps. We have derived the dispersion relation in a compact form for the S-shaped warps and the bowl-shaped distribution (described by m=1 and m=0 mode respectively ) in galactic disk embedded in a dark matter halo. We then performed the numerical modal analysis and used the linear and time-dependent superposition principle to generate asymmetric warps in the disk. We show that a rich variety of possible asymmetries in the z-distribution of the spiral galaxies can naturally arise due to a dynamical wave interference between the first two bending modes (i.e. m=0 and m=1 ) in the disk. The resulting values of the asymmetry index agree well with the recent observations. For details, see Saha, K. & Jog, C.J. 2006, A & A, 446, 897. We then study the dependence of the asymmetry index on the dark matter halo parameters. We show that the asymmetric warps are more pronounced when the dark matter content within the optical disk is lower as in early-type galaxies, and vice-versa. Thus we find that by studying the values of the asymmetry index ( which is easy to measure ) in disk galaxies it is possible to