The Three-Dimensional Structure of the Small Magellanic Cloud

Subramanian, Smitha; Subramaniam, Annapurni

doi:10.1088/0004-637x/744/2/128

Cited by 121 publications

(164 citation statements)

References 51 publications

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“…8-10. The 3D structure of the SMC was shown to be complex (Subramanian & Subramaniam 2012), with a spread in depth of about 14 kpc, and an inclination along the main axis with the north-eastern portion towards the observer. The five clusters studied in this work follow this dispersion, in particular for West Halo clusters, where we found distances between ∼54 and 63 kpc, revealing that more statistics on this region are needed in order to better describe the 3D structure of the SMC.…”

Section: The Age-metallicity Relation and Spatial Distributionmentioning

confidence: 98%

Self-consistent physical parameters for five intermediate-age SMC stellar clusters from CMD modelling

Dias

Kerber

Barbuy

et al. 2014

A&A

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Context. Stellar clusters in the Small Magellanic Cloud (SMC) are useful probes for studying the chemical and dynamical evolution of this neighbouring dwarf galaxy, enabling inspection of a large period covering over 10 Gyr. Aims. The main goals of this work are the derivation of age, metallicity, distance modulus, reddening, core radius, and central density profiles for six sample clusters, in order to place them in the context of the Small Cloud evolution. The studied clusters are AM 3, HW 1, HW 34, HW 40, Lindsay 2, and Lindsay 3; HW 1, HW 34, and Lindsay 2 are studied for the first time. Methods. Optical colour-magnitude diagrams (V, B − V CMDs) and radial density profiles were built from images obtained with the 4.1 m Southern Astrophysical Research (SOAR) telescope, reaching V ∼ 23. The determination of structural parameters were carried out by applying King profile fitting. The other parameters were derived in a self-consistent way by means of isochrone fitting, which uses likelihood statistics to identify the synthetic CMDs that best reproduce the observed ones. Membership probabilities were determined comparing the cluster and control field CMDs. Completeness and photometric uncertainties were obtained by performing artificial star tests. Results. The results confirm that these clusters (except HW 34, identified as a field fluctuation) are intermediate-age clusters, with ages between 1.2 Gyr (Lindsay 3) and ∼5.0 Gyr (HW 1). In particular HW 1, Lindsay 2 and Lindsay 3 are located in a region that we called West Halo, where studies of ages and metallicity gradients are still lacking. Moreover, Lindsay 2 was identified as a moderately metal-poor cluster with [Fe/H] = −1.4 ± 0.2 dex, lower than expected from the age-metallicity relation by Pagel & Tautvaisiene (1998). We also found distances varying from ∼53 kpc to 66 kpc, compatible with the large depth of the SMC.

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Section: The Age-metallicity Relation and Spatial Distributionmentioning

confidence: 98%

Self-consistent physical parameters for five intermediate-age SMC stellar clusters from CMD modelling

Dias

Kerber

Barbuy

et al. 2014

A&A

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“…The Small Magellanic Cloud (SMC), in particular, has an intriguing structure with a large extent along the line of sight (e.g. Subramanian & Subramaniam 2012;Nidever et al 2013;de Grijs & Bono 2015, and references therein) and a morphology that clearly depends on stellar population age (e.g. Cioni et al 2000a;Zaritsky et al 2000;Dobbie et al 2014;Subramanian & Subramaniam 2015;Deb et al 2015;Rubele et al 2015).…”

Section: Introductionmentioning

confidence: 99%

The VMC survey

Cioni

Bekki

Girardi

et al. 2016

A&A

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Aims. In this study we use multi-epoch near-infrared observations from the VISTA survey of the Magellanic Cloud system (VMC) to measure the proper motions of different stellar populations in a tile of 1.5 deg 2 in size in the direction of the Galactic globular cluster 47 Tuc. We obtain the proper motion of the cluster itself, of the Small Magellanic Cloud (SMC), and of the field Milky Way stars. Methods. Stars of the three main stellar components are selected according to their spatial distributions and their distributions in colour−magnitude diagrams. Their average coordinate displacement is computed from the difference between multiple K s -band observations for stars as faint as K s = 19 mag. Proper motions are derived from the slope of the best-fitting line among ten VMC epochs over a time baseline of ∼1 yr. Background galaxies are used to calibrate the absolute astrometric reference frame. Results. The resulting absolute proper motion of 47 Tuc is (μ α cos(δ), μ δ ) = (+7.26 ± 0.03, −1.25 ± 0.03) mas yr −1 . This measurement refers to about 35 000 sources distributed between 10 and 60 from the cluster centre. For the SMC we obtain (μ α cos(δ), μ δ ) = (+1.16 ± 0.07, −0.81 ± 0.07) mas yr −1 from about 5250 red clump and red giant branch stars. The absolute proper motion of the Milky Way population in the line of sight (l = 305.9, b = −44.9) of this VISTA tile is (μ α cos(δ), μ δ ) = (+10.22 ± 0.14, −1.27 ± 0.12) mas yr −1 and has been calculated from about 4000 sources. Systematic uncertainties associated with the astrometric reference system are 0.18 mas yr −1 . Thanks to the proper motion we detect 47 Tuc stars beyond its tidal radius.

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“…These results suggest that the stellar component follows a spheroidal distribution, whereas the gas is rotating in a disc-like structure. Furthermore, the SMC presents a significant line-of-sight depth, ranging from ∼6−14 kpc in the inner parts (Crowl et al 2001;Subramanian & Subramaniam 2012) to ∼23 kpc in the eastern parts along the Magellanic bridge (Nidever et al 2013). It is possible to find stars ∼12 kpc closer than the bulk of SMC stars in the direction of the bridge.…”

Section: Introductionmentioning

confidence: 99%

SMC west halo: a slice of the galaxy that is being tidally stripped?

Dias

Kerber

Barbuy

et al. 2016

A&A

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Context. The evolution and structure of the Magellanic Clouds is currently under debate. The classical scenario in which both the Large and Small Magellanic Clouds (LMC, SMC) are orbiting the Milky Way has been challenged by an alternative in which the LMC and SMC are in their first close passage to our Galaxy. The clouds are close enough to us to allow spatially resolved observation of their stars, and detailed studies of stellar populations in the galaxies are expected to be able to constrain the proposed scenarios. In particular, the west halo (WH) of the SMC was recently characterized with radial trends in age and metallicity that indicate tidal disruption. Aims. We intend to increase the sample of star clusters in the west halo of the SMC with homogeneous age, metallicity, and distance derivations to allow a better determination of age and metallicity gradients in this region. Positions are compared with the orbital plane of the SMC from models. Methods. Comparisons of observed and synthetic V(B − V) colour-magnitude diagrams were used to derive age, metallicity, distance, and reddening for star clusters in the SMC west halo. Observations were carried out using the 4.1 m SOAR telescope. Photometric completeness was determined through artificial star tests, and the members were selected by statistical comparison with a control field. Results. We derived an age of 1.23 ± 0.07 Gyr and [Fe/H] = −0.87 ± 0.07 for the reference cluster NGC 152, compatible with literature parameters. Age and metallicity gradients are confirmed in the WH: 2.6 ± 0.6 Gyr/• and −0.19 ± 0.09 dex/ • , respectively. The age-metallicity relation for the WH has a low dispersion in metallicity and is compatible with a burst model of chemical enrichment. All WH clusters seem to follow the same stellar distribution predicted by dynamical models, with the exception of AM-3, which should belong to the counter-bridge. Brück 6 is the youngest cluster in our sample. It is only 130 ± 40 Myr old and may have been formed during the tidal interaction of SMC-LMC that created the WH and the Magellanic bridge. Conclusions. We suggest that it is crucial to split the SMC cluster population into groups: main body, wing and bridge, counter-bridge, and WH. This is the way to analyse the complex star formation and dynamical history of our neighbour. In particular, we show that the WH has clear age and metallicity gradients and an age-metallicity relation that is also compatible with the dynamical model that claims a tidal influence of the LMC on the SMC.

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The Three-Dimensional Structure of the Small Magellanic Cloud

Cited by 121 publications

References 51 publications

Self-consistent physical parameters for five intermediate-age SMC stellar clusters from CMD modelling

Self-consistent physical parameters for five intermediate-age SMC stellar clusters from CMD modelling

The VMC survey

SMC west halo: a slice of the galaxy that is being tidally stripped?

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