SMASHing the LMC: A Tidally-induced Warp in the Outer LMC and a Large-scale Reddening Map

We present a study of the three-dimensional (3D) structure of the Large Magellanic Cloud (LMC) using ~2.2 million red clump (RC) stars selected from the Survey of the MAgellanic Stellar History. To correct for line-of-sight dust extinction, the intrinsic RC color and magnitude and their radial dependence are carefully measured by using internal nearly dust-free regions. These are then used to construct an accurate 2D reddening map (165 square degrees with ~10 arcmin resolution) of the LMC disk and the 3D spatial distribution of RC stars. An inclined disk model is fit to the 2D distance map yielding a best-fit inclination angle i = 25.86(+0.73,-1.39) degrees with random errors of +\-0.19 degrees and line-of-nodes position angle theta = 149.23(+6.43,-8.35) degrees with random errors of +/-0.49 degrees. These angles vary with galactic radius, indicating that the LMC disk is warped and twisted likely due to the repeated tidal interactions with the Small Magellanic Cloud (SMC). For the first time, our data reveal a significant warp in the southwestern part of the outer disk starting at rho ~ 7 degrees that departs from the defined LMC plane up to ~4 kpc toward the SMC, suggesting that it originated from a strong interaction with the SMC. In addition, the inner disk encompassing the off-centered bar appears to be tilted up to 5-15 degrees relative to the rest of the LMC disk. These findings on the outer warp and the tilted bar are consistent with the predictions from the Besla et al. simulation of a recent direct collision with the SMC.Comment: 25 pages, 15 figures, published in Ap

SMASHing the low surface brightness SMC

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Exploring the Very Extended Low-surface-brightness Stellar Populations of the Large Magellanic Cloud with SMASH

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SMASH 1: A Very Faint Globular Cluster Disrupting in the Outer Reaches of the LMC?

We present the discovery of a very faint stellar system, SMASH 1, that is potentially a satellite of the Large Magellanic Cloud. Found within the Survey of the Magellanic Stellar History (SMASH), SMASH 1 is a compact ({r}_{h}={9.1}_{-3.4}^{+5.9}____,____mathrm{pc}) and very low luminosity ({M}_{V}=-1.0____pm 0.9, {L}_{V}={10}^{2.3____pm 0.4}____,{L}_{____odot }) stellar system that is revealed by its sparsely populated main sequence and a handful of red giant branch candidate member stars. The photometric properties of these stars are compatible with a metal-poor ([____mathrm{Fe}/{____rm{H}}]=-2.2) and old (13 Gyr) isochrone located at a distance modulus of ~18.8, i.e., a distance of ____sim 57____,____mathrm{kpc}. Situated at 11fdg3 from the LMC in projection, its three-dimensional distance from the Cloud is ____sim 13____,____mathrm{kpc}, consistent with a connection to the LMC, whose tidal radius is at least 16____,____mathrm{kpc}. Although the nature of SMASH 1 remains uncertain, its compactness favors it being a stellar cluster and hence dark-matter free. If this is the case, its dynamical tidal radius is only ____lesssim 19____,____mathrm{pc} at this distance from the LMC, and smaller than the system's extent on the sky. Its low luminosity and apparent high ellipticity (____epsilon ={0.62}_{-0.21}^{+0.17}) with its major axis pointing toward the LMC may well be the tell-tale sign of its imminent tidal demise

Survey of the MAgellanic Stellar History -- SMASH

Over the last several years, various discoveries have drastically altered our view of the iconic Magellanic Clouds (MCs), the nearest interacting galaxy system. The best evidence is now that they are on first infall into the Milky Way, that their stellar populations extend much further than previously thought, and that they suffered a close collision that tore out both the well-known Magellanic Stream and a large amount of still undetected stellar debris. Here we propose a community DECam survey of the Clouds mapping 480 deg^2 (distributed over 2400 deg^2 at 20% filling factor) to 24th mag griz (and u$ 23) that will supplement the 5000 deg^2 Dark Energy Survey's partial coverage of the Magellanic periphery, allowing us to map the expected stellar debris and extended populations with unprecedented fidelity. We have already conducted a pilot project demonstrating that DECam will allow us to: (1) Map the stellar periphery of the MCs with old main-sequence turnoff stars to a surface brightness limit of 35 mag/arcsec^2, revealing relics of their formation and past interactions. (2) Identify the stellar component of the Magellanic Stream and Leading Arm for the first time, if they exist, making them the only Galactic halo tracers with both gaseous and stellar components. (3) Derive spatially-resolved star formation histories covering all ages out to large radii of the MCs that will further complement our understanding of their formation. The combination of this survey and DES data will allow us to uncover a multitude of stellar structure that will unveil the complex and dramatic history of these two dwarf galaxies, while enabling a broad spectrum of community-led projects