The Odd Offset between the Galactic Disk and Its Bar in NGC 3906
  We use mid-infrared 3.6 and 4.5microns imaging of NGC 3906 from the Spitzer
Survey of Stellar Structure in Galaxies (S4G) to understand the nature of an
unusual offset between its stellar bar and the photometric center of an
otherwise regular, circular outer stellar disk. We measure an offset of ~720 pc
between the center of the stellar bar and photometric center of the stellar
disk; the bar center coincides with the kinematic center of the disk determined
from previous HI observations. Although the undisturbed shape of the disk
suggests that NGC 3906 has not undergone a significant merger event in its
recent history, the most plausible explanation for the observed offset is an
interaction. Given the relatively isolated nature of NGC 3906 this interaction
could be with dark matter sub structure in the galaxy's halo or from a recent
interaction with a fast moving neighbor which remains to be identified.
Simulations aimed at reproducing the observed offset between the stellar bar /
kinematic center of the system and the photometric center of the disk are
necessary to confirm this hypothesis and constrain the interaction history of
the galaxy.
