Low Surface Brightness Imaging of the Magellanic System: Imprints of Tidal Interactions between the Clouds in the Stellar Periphery

TL;DR

This study uses deep optical imaging and simulations to analyze the stellar substructures in the outskirts of the Magellanic Clouds, revealing that interactions with the SMC shape their asymmetric features and providing insights into their interaction history.

Contribution

It combines low-cost wide-field imaging with detailed simulations to demonstrate that dwarf-dwarf interactions create persistent asymmetric stellar structures in galaxy pairs.

Findings

Stellar arcs and spiral arms are present in the LMC's northern periphery.

Repeated interactions with the SMC explain the observed asymmetries.

Asymmetric structures can persist for 1-2 Gyr after dwarf mergers.

Abstract

We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in the northern periphery, with no comparable counterparts in the South. We compare these data to detailed simulations of the LMC disk outskirts, following interactions with its low mass companion, the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field. The simulations are used to assess the origin of the northern structures, including also the low density stellar arc recently identified in the DES data by Mackey et al. 2015 at ~ 15 degrees. We conclude that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to constrain the LMC's interaction history with and impact parameter of the SMC. More generally, we find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for 1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are driven by dwarf-dwarf interactions.