Tidally Induced Offset Disks in Magellanic Spiral Galaxies

TL;DR

This study uses simulations to show that interactions between dwarf galaxies can cause long-lasting asymmetries and offset bars in Magellanic spiral galaxies, explaining observed features like in the LMC.

Contribution

It demonstrates that dwarf-dwarf interactions can produce offset bars and asymmetries lasting for nearly 2 Gyrs, clarifying the origin of Magellanic galaxy features.

Findings

Disk asymmetries persist for nearly 2 Gyrs.

The bar center coincides with the dynamical center.

Offset bars can be explained by past interactions.

Abstract

Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar, and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations we consider a dwarf-dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate here the relation between the dynamical, stellar and gaseous disk center and the bar. In all our simulations the bar center always coincides with the dynamical center, while the stellar disk becomes highly asymmetric during the encounter causing the photometric center of the Magellanic galaxy disk to become mismatched with both the bar and the dynamical center. The disk asymmetries persist for almost 2 Gyrs, the time that it takes for the disk to be re-centered with the bar, and well after the companion has passed. This explains the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, these results, once applied to the LMC, suggest that the dynamical center should reside in the bar center instead of the HI center as previously assumed, pointing to a variation in the current estimate of the north component of the LMC proper motion.