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

Choi, Yumi; Nidever, David L.; Olsen, Knut; Besla, Gurtina; Blum, Robert; Zaritsky, Dennis; Cioni, M. R. L.; Marel, Roeland P. van der; Bell, Eric F.; Johnson, L. Clifton; Vivas, A. Katherina; Walker, A. R.; Boer, T. J. L. de; Noel, Noelia E. D.; Monachesi, Antonela; Gallart, Carme; Monelli, M.; Stringfellow, Guy S.; Massana, Pol; Martínez–Delgado, David; Muñoz, Ricardo R.

doi:10.3847/1538-4357/aaed1f

Cited by 40 publications

(30 citation statements)

References 91 publications

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“…emanating symmetrically from the bar. This residual feature is largely coincident with the ring-like overdensity uncovered by Choi et al (2018a). Through modeling the LMC stellar density with a disk and bar component, their residuals revealed a structure akin to ours composed of stars older than ∼1 Gyr.…”

Section: Metallicity Gradientssupporting

confidence: 56%

“…The history of the Large and Small Magellanic Clouds is fraught with complex interactions and, being our nearest example of such a system, provides us with a vital laboratory for detailed study of interacting dwarf irregulars. The Large Magellanic Cloud (LMC) is generally well described by a planar, inclined disk, yet it still displays a host of deviations from this simple picture; it has long been observed to display one dominant spiral arm (see, e.g., de Vaucouleurs 1955;de Vaucouleurs & Freeman 1972) as well as an off-centered stellar bar (e.g., Zhao & Evans 2000;Nikolaev et al 2004) and shell/ ring-like features (e.g., de Vaucouleurs 1955;Irwin 1991;Choi et al 2018a). In a broad sense, the young stellar populations of the LMC exhibit a clumpy structure, largely congregating centrally around the bar and spiral arm, with little evidence for them residing in the outer regions (see, e.g., Moni Bidin et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Magellanic Mayhem: Metallicities and Motions

Grady

Belokurov

Evans

2021

ApJ

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We assemble a catalog of Magellanic Cloud red giants from Data Release 2 of the Gaia mission and, utilizing machine-learning methods, obtain photometric metallicity estimates for them. In doing so, we are able to chemically map the entirety of the Magellanic System at once. Our maps reveal a plethora of substructure within our red giant sample, with the Large Magellanic Cloud (LMC) bar and spiral arm being readily apparent. We uncover a curious spiral-like feature in the southern portion of the LMC disk, hosting relatively metal-rich giants and likely a by-product of historic encounters with the Small Magellanic Cloud (SMC). Modeling the LMC as an inclined thin disk, we find a shallow metallicity gradient of −0.048 ± 0.001 dex kpc −1 out to ∼12°from the center of the dwarf. We see evidence that the SMC is disrupting, with its outer isodensity contours displaying the S-shape symptomatic of tidal stripping. On studying the proper motions of the SMC giants, we observe a population of them being violently dragged toward the larger Cloud. The perturbed stars predominantly lie in front of the SMC, and we interpret that they exist as a tidal tail of the dwarf, trailing in its motion and undergoing severe disruption from the LMC. We find the metallicity structure in the Magellanic Bridge region to be complex, with evidence for a composite nature in this stellar population, consisting of both LMC and SMC debris.Unified Astronomy Thesaurus concepts: Galaxies (573); Local Group (929); Large Magellanic Cloud (903); Small Magellanic Cloud (1468)

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Section: Metallicity Gradientssupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Magellanic Mayhem: Metallicities and Motions

Grady

Belokurov

Evans

2021

ApJ

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“…The arms are well traced by stellar populations younger than a few million years, while old stellar populations instead show external features that may be associated with a ring-like structure (e.g. Choi et al 2018). The long-term stability of the prominent spiral arm was studied by Ruiz-Lara et al (2020) using deep optical photometry to derive the star formation history throughout the galaxy.…”

Section: Spiral Arms In the Large Magellanic Cloudmentioning

confidence: 99%

Gaia Early Data Release 3

Luri

Chemin

Clementini³

et al. 2021

A&A

104

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Context. This work is part of the Gaia Data Processing and Analysis Consortium papers published with the Gaia Early Data Release 3 (EDR3). It is one of the demonstration papers aiming to highlight the improvements and quality of the newly published data by applying them to a scientific case. Aims. We use the Gaia EDR3 data to study the structure and kinematics of the Magellanic Clouds. The large distance to the Clouds is a challenge for the Gaia astrometry. The Clouds lie at the very limits of the usability of the Gaia data, which makes the Clouds an excellent case study for evaluating the quality and properties of the Gaia data. Methods. The basis of our work are two samples selected to provide a representation as clean as possible of the stars of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The selection used criteria based on position, parallax, and proper motions to remove foreground contamination from the Milky Way, and allowed the separation of the stars of both Clouds. From these two samples we defined a series of subsamples based on cuts in the colour-magnitude diagram; these subsamples were used to select stars in a common evolutionary phase and can also be used as approximate proxies of a selection by age. Results. We compared the Gaia Data Release 2 and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insightsinto features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones.

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“…The observed number count map itself already shows some interesting structures. We investigate the LMC disk structure for various stellar populations, such as RC and young MS, by modeling their observed star count map as a 2D projection of a tilted elliptical disk model in a separate paper (Choi et al 2018).…”

Section: Selection Of Rc Starsmentioning

confidence: 99%

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

Choi

Nidever

Olsen

et al. 2018

ApJ

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124

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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 deg 2 area with ∼10 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 • and line-ofnodes position angle θ = 149.23 +6.43 −8.35 degrees with random errors of ±0.49 • . 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 ρ ∼7 • 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 • 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.

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

Cited by 40 publications

References 91 publications

Magellanic Mayhem: Metallicities and Motions

Magellanic Mayhem: Metallicities and Motions

Gaia Early Data Release 3

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

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