The VMC survey: XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae

Maria-Rosa L. Cioni; Kenji Bekki; Léo Girardi; Richard De Grijs; Mike J. Irwin; Valentin D. Ivanov; Marcella Marconi; Joana M. Oliveira; Andrés E. Piatti; Vincenzo Ripepi; Jacco Th Van Loon

doi:10.1051/0004-6361/201527004

The VMC survey: XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae

Maria-Rosa L. Cioni, Kenji Bekki, Léo Girardi, Richard De Grijs, Mike J. Irwin, Valentin D. Ivanov, Marcella Marconi, Joana M. Oliveira, Andrés E. Piatti, Vincenzo Ripepi, Jacco Th Van Loon

Research output: Contribution to journal › Article › peer-review

25 Citations (Scopus)

Abstract

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 deg² 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_αcos(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_αcos(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_αcos(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.

Original language	English
Article number	A77
Number of pages	16
Journal	Astronomy and Astrophysics
Volume	586
DOIs	https://doi.org/10.1051/0004-6361/201527004
Publication status	Published - 1 Feb 2016
Externally published	Yes

Keywords

Globular clusters: individual: 47 Tucanae
Magellanic Clouds
Proper motions
Surveys

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10.1051/0004-6361/201527004

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Cioni, M.-R. L., Bekki, K., Girardi, L., De Grijs, R., Irwin, M. J., Ivanov, V. D., Marconi, M., Oliveira, J. M., Piatti, A. E., Ripepi, V., & Van Loon, J. T. (2016). The VMC survey: XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae. Astronomy and Astrophysics, 586, Article A77. https://doi.org/10.1051/0004-6361/201527004

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title = "The VMC survey: XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae",

abstract = "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 deg2 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 Ks-band observations for stars as faint as Ks = 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 (μαcos(δ), μδ) = (+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 (μαcos(δ), μδ) = (+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 (μαcos(δ), μδ) = (+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.",

keywords = "Globular clusters: individual: 47 Tucanae, Magellanic Clouds, Proper motions, Surveys",

author = "Cioni, {Maria-Rosa L.} and Kenji Bekki and L{\'e}o Girardi and {De Grijs}, Richard and Irwin, {Mike J.} and Ivanov, {Valentin D.} and Marcella Marconi and Oliveira, {Joana M.} and Piatti, {Andr{\'e}s E.} and Vincenzo Ripepi and {Van Loon}, {Jacco Th}",

year = "2016",

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doi = "10.1051/0004-6361/201527004",

language = "English",

volume = "586",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

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TY - JOUR

T1 - The VMC survey

T2 - XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae

AU - Cioni, Maria-Rosa L.

AU - Bekki, Kenji

AU - Girardi, Léo

AU - De Grijs, Richard

AU - Irwin, Mike J.

AU - Ivanov, Valentin D.

AU - Marconi, Marcella

AU - Oliveira, Joana M.

AU - Piatti, Andrés E.

AU - Ripepi, Vincenzo

AU - Van Loon, Jacco Th

PY - 2016/2/1

Y1 - 2016/2/1

N2 - 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 deg2 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 Ks-band observations for stars as faint as Ks = 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 (μαcos(δ), μδ) = (+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 (μαcos(δ), μδ) = (+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 (μαcos(δ), μδ) = (+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.

AB - 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 deg2 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 Ks-band observations for stars as faint as Ks = 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 (μαcos(δ), μδ) = (+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 (μαcos(δ), μδ) = (+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 (μαcos(δ), μδ) = (+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.

KW - Globular clusters: individual: 47 Tucanae

KW - Magellanic Clouds

KW - Proper motions

KW - Surveys

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U2 - 10.1051/0004-6361/201527004

DO - 10.1051/0004-6361/201527004

M3 - Article

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SN - 0004-6361

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JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A77

ER -

The VMC survey: XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae

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