Growing Live Disks within Cosmologically Assembling Asymmetric Halos: Washing Out the Halo Prolateness

We study the growth of galactic disks in live triaxial DM halos. The haloshave been assembled through constrained realizations method and evolved fromthe linear regime using cosmological simulations. The `seed' disks have beeninserted at redshift z=3 and increased in mass tenfold over various timeperiods, ~1-3 Gyr, with the halo responding quasi-adiabatically to thisprocess. We follow the dynamical and secular evolution of the disk-halo systemand analyze changes in the most important parameters, like 3-D DM shapes,stellar and DM radial density profiles, stellar bar development, etc. We findthat a growing disk is responsible for washing out the halo prolateness and fordiluting its flatness over a period of time comparable to the disk growth.Moreover, we find that a disk which contributes more to the overall rotationcurve in the system is also more efficient in axisymmetrizing the halo, withoutaccelerating the halo figure rotation. The observational corollary is that themaximal disks probably reside in nearly axisymmetric halos, while disks whoserotation is dominated by the halo at all radii are expected to reside in moreprolate halos. The halo shape is sensitive to the final disk mass, but isindependent of how the seed disk is introduced into the system. We also expectthat the massive disks are subject to a bar instability, while light disks havethis instability damped by the halo triaxiality. Implications to thecosmological evolution of disks embedded in asymmetric halos are discussed andso are the corollaries for the observed fraction of stellar bars. Finally, thehalo responds to the stellar bar by developing a gravitational wake -- a`ghost' bar of its own which is almost in-phase with that in the disk.