Examinando por Autor "Santos, J.F.C."

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    The VISCACHA survey - VII. Assembly history of the Magellanic Bridge and SMC Wing from star clusters
    (Oxford University Press, 2023-09-01) Oliveira, R.A.P.; Maia, F.F.S.; Barbuy, B.; Dias, B.; Santos, J.F.C.; Souza, S.O.; Kerber, L.O.; Bica, E.; Sanmartim, D.; Quint, B.; Fraga, L.; Armond, T.; Minniti, D.; Parisi, M.C.; Katime Santrich, O.J.; Angelo, M.S.; Perez-Villegas, A.; De Bórtoli, B.J.
    The formation scenario of the Magellanic Bridge during an encounter between the Large and Small Magellanic Clouds ∼200 Myr ago, as proposed by N-body models, would be imprinted in the chemical enrichment and kinematics of its stars and sites of ongoing star formation along its extension. We present an analysis of 33 Bridge star clusters using photometry obtained with the SOAR 4-m telescope equipped with adaptive optics for the VISCACHA survey. We performed a membership selection and derived self-consistent ages, metallicities, distances, and reddening values via statistical isochrone fitting, as well as tidal radii and integrated masses from structure analysis. Two groups are clearly detected: 13 well-studied clusters older than the Bridge, with 0.5-6.8 Gyr and dex, probably formed in situ. The old clusters follow the overall age and metallicity gradients of the SMC, whereas the younger ones are uniformly distributed along the Bridge. The main results are as follows: (i) we derive ages and metallicities for the first time for 9 and 18 clusters, respectively; (ii) we detect two metallicity dips in the age-metallicity relation of the Bridge at ∼200 Myr and 1.5 Gyr ago for the first time, possibly chemical signatures of the formation of the Bridge and Magellanic Stream; (iii) we estimate a minimum stellar mass for the Bridge of 3-5 × 105 M⊙; (iv) we confirm that all the young Bridge clusters at RA and 15 clusters with < Myr and -0.5 are metal-rich with dex. © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
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    The VISCACHA survey-II. Structure of star clusters in the Magellanic Clouds periphery
    (Oxford University Press, 2020-10) Santos, J.F.C.; Maia, F.F.S.; Dias, B.; Kerber, L.D.O.; Piatti, A.E.; Bica, E.; Angelo, M.S.; Minniti, D.; Pérez-Villegas, A.; Roman-Lopes, A.; Westera, P.; Fraga L.
    We provide a homogeneous set of structural parameters of 83 star clusters located at the periphery of the Small Magellanic Cloud (SMC) and the Large Magellanic Cloud (LMC). The clusters' stellar density and surface brightness profiles were built from deep, AO assisted optical images, and uniform analysis techniques. The structural parameters were obtained from King and Elson et al. model fittings. Integrated magnitudes and masses (for a subsample) are also provided. The sample contains mostly low surface brightness clusters with distances between 4.5 and 6.5 kpc and between 1 and 6.5 kpc from the LMC and SMC centres, respectively. We analysed their spatial distribution and structural properties, comparing them with those of inner clusters. Half-light and Jacobi radii were estimated, allowing an evaluation of the Roche volume tidal filling. We found that: (i) for our sample of LMC clusters, the tidal radii are, on average, larger than those of inner clusters from previous studies; (ii) the core radii dispersion tends to be greater for LMC clusters located towards the southwest, with position angles of ∼200° and about ∼5° from the LMC centre, i.e.Those LMC clusters nearer to the SMC; (iii) the core radius evolution for clusters with known age is similar to that of inner clusters; (iv) SMC clusters with galactocentric distances closer than 4 kpc are overfilling; (v) the recent Clouds collision did not leave marks on the LMC clusters' structure that our analysis could reveal. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
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    The VISCACHA survey-IV. the SMC West Halo in 8D
    (Oxford University Press, 2022-05-01) Dias, B.; Parisi, M.C.; Angelo, M.; Maia, F.; Oliveira, R.A.P.; Souza, S.O.; Kerber, L.O.; Santos, J.F.C.; Perez-Villegas, A.; Sanmartim, D.; Quint, B.; Fraga, L.; Barbuy, B.; Bica, E.; Santrich, O. J. Katime; Hernandez-Jimenez, J.A.; Geisler, D.; Minniti, D.; De Bórtoli, B.J.; Bassino, L.P.; Rocha, J.P.
    The structure of the Small Magellanic Cloud (SMC) is very complex, in particular in the periphery that suffers more from the interactions with the Large Magellanic Cloud (LMC). A wealth of observational evidence has been accumulated revealing tidal tails and bridges made up of gas, stars, and star clusters. Nevertheless, a full picture of the SMC outskirts is only recently starting to emerge with a 6D phase-space map plus age and metallicity using star clusters as tracers. In this work, we continue our analysis of another outer region of the SMC, the so-called West Halo, and combined it with the previously analysed Northern Bridge. We use both structures to define the Bridge and Counter-bridge trailing and leading tidal tails. These two structures are moving away from each other, roughly in the SMC-LMC direction. The West Halo form a ring around the SMC inner regions that goes up to the background of the Northern Bridge shaping an extended layer of the Counter-bridge. Four old Bridge clusters were identified at distances larger than 8 kpc from the SMC centre moving towards the LMC, which is consistent with the SMC-LMC closest distance of 7.5 kpc when the Magellanic Bridge was formed about 150Myr ago; this shows that the Magellanic Bridge was not formed only by pulled gas, but it also removed older stars from the SMC during its formation. We also found age and metallicity radial gradients using projected distances on sky, which are vanished when we use the real 3D distances. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.