Formation of the off-center bar in the Large Magellanic Cloud: A collision with a dark satellite ?

Abstract

Recent observations on structural properties of the Large Magellanic Cloud (LMC) based on the Deep Near-Infrared Southern Sky Survey (DENIS) and Two Micron All-Sky Survey (2MASS) have revealed that the LMC has an off-center bar even in the older stellar populations. Previous dynamical models including tidal interaction between the LMC, the Small Magellanic Cloud (SMC), and the Galaxy, however, did not reproduce so well the older off-center bar. We here show that the off-center bar can be formed if the LMC with an already existing bar can collide with a low-mass Galactic subhalo as massive as 5 * 10^8 M_sun (corresponding roughly to a few % of the LMC mass). The simulated stellar distribution after the collision appears to show an ``off-center bar'', not because the center of the bar significantly deviates from the dynamical center of the LMC, but because the underlying stellar distribution of the disk is significantly asymmetric with respect to the center of the bar. We discuss whether off-center bars observed in Magellanic-type dwarf galaxies can be formed as a result of tidal interaction with low-mass halos with no or little visible matters.