Title: SMASHing THE LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk Show Chinese title

Title: SMASHing the LMC：在LMC盘中绘制环状恒星过密度的分布

Abstract: 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. Show Chinese abstract

Abstract: 我们使用来自麦哲伦星系恒星历史调查（SMASH）和暗能量调查的数据，研究了大麦哲伦云（LMC）盘的恒星结构。 我们在红团星计数图中检测到一个环状的恒星密度增强，在半径约6度（在LMC距离处约为5.2千秒差距）的位置，该增强在位置角上连续覆盖约270度，仅受限于当前数据的覆盖范围。 该密度增强的幅度高达其下方平滑盘的2.5倍。 这种结构可能与de Vaucouleurs发现的多条旋臂有关。 我们发现该密度增强与中等年龄的星团有空间相关性，但与年轻的（小于1 Gyr）主序星没有相关性，表明与该密度增强相关的恒星种群是中等年龄或更老的。 我们对LMC密度增强的发现可以通过两种不同的环状密度增强形成机制来解释：（1）该密度增强是由不对称单旋臂环绕LMC主体形成的，这由过去十亿年内与小麦哲伦云（SMC）的多次遭遇引发，或者（2）该密度增强最近由于与SMC的直接碰撞而形成。 尽管密度增强的测量特性本身无法区分这两种候选情景，但与这两种情景的一致性表明，环状密度增强很可能是与SMC潮汐相互作用的结果，而不是与银河系晕的相互作用。