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1. The Large Magellanic Cloud stellar content with SMASH: I. Assessing the stability of the Magellanic spiral arms

   https://doi.org/10.1051/0004-6361/202038392  

   Ruiz-Lara, T. ; Gallart, C. ; Monelli, M. ; Nidever, D. ; Dorta, A. ; Choi, Y. ; Olsen, K. ; Besla, G. ; Bernard, E. J. ; Cassisi, S. ; et al ( July 2020 , Astronomy & Astrophysics)

   The Large Magellanic Cloud (LMC) is the closest and most studied example of an irregular galaxy. Among its principal defining morphological features, its off-centred bar and single spiral arm stand out, defining a whole family of galaxies known as the Magellanic spirals (Sm). These structures are thought to be triggered by tidal interactions and possibly maintained via gas accretion. However, it is still unknown whether they are long-lived stable structures. In this work, by combining photometry that reaches down to the oldest main sequence turn-off in the colour-magnitude diagrams (CMD, up to a distance of ∼4.4 kpc from the LMC centre) from the SMASH survey and CMD fitting techniques, we find compelling evidence supporting the long-term stability of the LMC spiral arm, dating the origin of this structure to more than 2 Gyr ago. The evidence suggests that the close encounter between the LMC and the Small Magellanic Cloud (SMC) that produced the gaseous Magellanic Stream and its Leading Arm also triggered the formation of the LMC’s spiral arm. Given the mass difference between the Clouds and the notable consequences of this interaction, we can speculate that this should have been one of their closest encounters. These results set important constraints on the timing of LMC-SMC collisions, as well as on the physics behind star formation induced by tidal encounters. 

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2. The intrinsic reddening of the Magellanic Clouds as traced by background galaxies – II. The Small Magellanic Cloud

   https://doi.org/10.1093/mnras/staa2786  

   Bell, Cameron P ; Cioni, Maria-Rosa L ; Wright, A H ; Rubele, Stefano ; Nidever, David L ; Tatton, Ben L ; van Loon, Jacco Th ; Zaritsky, Dennis ; Choi, Yumi ; Choudhury, Samyaday ; et al ( October 2020 , Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We present a map of the total intrinsic reddening across ≃34 deg2 of the Small Magellanic Cloud (SMC) derived using optical (ugriz) and near-infrared (IR; YJKs) spectral energy distributions (SEDs) of background galaxies. The reddening map is created using a subsample of 29 274 galaxies with low levels of intrinsic reddening based on the lephare χ2 minimization SED-fitting routine. We find statistically significant enhanced levels of reddening associated with the main body of the SMC compared with regions in the outskirts [ΔE(B − V) ≃ 0.3 mag]. A comparison with literature reddening maps of the SMC shows that, after correcting for differences in the volume of the SMC sampled, there is good agreement between our results and maps created using young stars. In contrast, we find significant discrepancies between our results and maps created using old stars or based on longer wavelength far-IR dust emission that could stem from biased samples in the former and uncertainties in the far-IR emissivity and the optical properties of the dust grains in the latter. This study represents one of the first large-scale categorizations of extragalactic sources behind the SMC and as such we provide the lephare outputs for our full sample of ∼500 000 sources. 

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3. The intrinsic reddening of the Magellanic Clouds as traced by background galaxies – III. The Large Magellanic Cloud

   https://doi.org/10.1093/mnras/stac1545  

   Bell, Cameron P ; Cioni, Maria-Rosa L ; Wright, Angus H ; Nidever, David L ; Chiang, I-Da ; Choudhury, Samyaday ; Groenewegen, Martin A ; Pennock, Clara M ; Choi, Yumi ; de Grijs, Richard ; et al ( June 2021 , Monthly Notices of the Royal Astronomical Society)

   We present a map of the total intrinsic reddening across ≃ 90 deg2 of the Large Magellanic Cloud (LMC) derived using optical (ugriz) and near-infrared (IR; YJKs) spectral energy distributions (SEDs) of background galaxies. The reddening map is created from a sample of 222,752 early-type galaxies based on the lephare χ2 minimization SED-fitting routine. We find excellent agreement between the regions of enhanced intrinsic reddening across the central (4 × 4 deg2) region of the LMC and the morphology of the low-level pervasive dust emission as traced by far-IR emission. In addition, we are able to distinguish smaller, isolated enhancements that are coincident with known star-forming regions and the clustering of young stars observed in morphology maps. The level of reddening associated with the molecular ridge south of 30 Doradus is, however, smaller than in the literature reddening maps. The reduced number of galaxies detected in this region, due to high extinction and crowding, may bias our results towards lower reddening values. Our map is consistent with maps derived from red clump stars and from the analysis of the star formation history across the LMC. This study represents one of the first large-scale categorisations of extragalactic sources behind the LMC and as such we provide the lephare outputs for our full sample of ∼ 2.5 million sources. 

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4. H α Distances to the Leading Arm of the Magellanic Stream

   https://doi.org/10.3847/1538-4357/ab6ef9  

   Antwi-Danso, Jacqueline ; Barger, Kathleen A. ; Haffner, L. Matthew ( March 2020 , The Astrophysical Journal)

   null (Ed.)
5. The Magellanic Edges Survey I: Description and first results

   https://doi.org/10.1093/mnras/staa2048  

   Cullinane, L R ; Mackey, A D ; Da Costa, G S ; Koposov, S E ; Belokurov, V ; Erkal, D ; Koch, A ; Kunder, A ; Nataf, D M ( September 2020 , Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We present an overview of, and first science results from, the Magellanic Edges Survey (MagES), an ongoing spectroscopic survey mapping the kinematics of red clump and red giant branch stars in the highly substructured periphery of the Magellanic Clouds. In conjunction with Gaia astrometry, MagES yields a sample of ~7000 stars with individual 3D velocities that probes larger galactocentric radii than most previous studies. We outline our target selection, observation strategy, data reduction, and analysis procedures, and present results for two fields in the northern outskirts (>10° on-sky from the centre) of the Large Magellanic Cloud (LMC). One field, located in the vicinity of an arm-like overdensity, displays apparent signatures of perturbation away from an equilibrium disc model. This includes a large radial velocity dispersion in the LMC disc plane, and an asymmetric line-of-sight velocity distribution indicative of motions vertically out of the disc plane for some stars. The second field reveals 3D kinematics consistent with an equilibrium disc, and yields Vcirc = 87.7 ± 8.0 km s−1 at a radial distance of ~10.5 kpc from the LMC centre. This leads to an enclosed mass estimate for the LMC at this radius of (1.8 ± 0.3) × 1010 M⊙. 

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