SMASHing THE LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk

• Main Authors: Choi, Yumi, Nidever, David L, Olsen, Knut, Besla, Gurtina, Blum, Robert D, Zaritsky, Dennis, Cioni, Maria-Rosa L, van der Marel, Roeland P, Bell, Eric F, Johnson, L. Clifton, Vivas, A. Katherina, Walker, Alistair R, de Boer, Thomas J. L, Noel, Noelia E. D, Monachesi, Antonela, Gallart, Carme, Monelli, Matteo, Stringfellow, Guy S, Massana, Pol, Martinez-Delgado, David, Munoz, Ricardo
• Format: Journal Article
• Language: English
• Published: 20-12-2018
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.1805.00481

2018 ApJ, 869, 125 We explore the stellar structure of the Large Magellanic Cloud (LMC) disk
using data from the Survey of the MAgellanic Stellar History (SMASH) and the
Dark Energy Survey. We detect a ring-like stellar overdensity in the red clump
star count map at a radius of ~6 degrees (~5.2 kpc at the LMC distance) that is
continuous over ~270 degrees in position angle and is only limited by the
current data coverage. The overdensity shows an amplitude up to 2.5 times
higher than that of the underlying smooth disk. This structure might be related
to the multiple arms found by de Vaucouleurs. We find that the overdensity
shows spatial correlation with intermediate-age star clusters, but not with
young (< 1 Gyr) main-sequence stars, indicating the stellar populations
associated with the overdensity are intermediate in age or older. Our findings
on the LMC overdensity can be explained by either of two distinct formation
mechanisms of a ring-like overdensity: (1) the overdensity formed out of an
asymmetric one-armed spiral wrapping around the LMC main body, which is induced
by repeated encounters with the Small Magellanic Cloud (SMC) over the last Gyr,
or (2) the overdensity formed very recently as a tidal response to a direct
collision with the SMC. Although the measured properties of the overdensity
alone cannot distinguish between the two candidate scenarios, the consistency
with both scenarios suggests that the ring-like overdensity is likely a product
of tidal interaction with the SMC, but not with the Milky Way halo.