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New Proper Motions of the Small Magellanic Cloud Using HST and Implications for Milky Way Mass

Published online by Cambridge University Press:  02 August 2018

P. Zivick
Affiliation:
Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; [email protected]
N. Kallivayalil
Affiliation:
Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; [email protected]
S. Linden
Affiliation:
Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; [email protected]
T. Fritz
Affiliation:
Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; [email protected]
G. Besla
Affiliation:
Steward Observatory, University of Arizona, Tucson, AZ, 85721, USA
R. P. van der Marel
Affiliation:
Space Telescope Science Institute, Baltimore, MD 21218, USA
S. Kozłowski
Affiliation:
Warsaw University Observatory, 00-478 Warszawa, Poland
M. C. Geha
Affiliation:
Yale Center for Astronomy & Astrophysics, New Haven, CT 06511, USA
C. S. Kochanek
Affiliation:
Department of Astronomy, The Ohio State University, Columbus, OH 43210, USA
J. Anderson
Affiliation:
Space Telescope Science Institute, Baltimore, MD 21218, USA
C. R. Alcock
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
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Abstract

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As new work on the proper motions (PMs) of the Large Magellanic Cloud (LMC) has come out, our view of the history of the Magellanic Clouds has evolved. We now believe they are on their first infall into the Milky Way (MW), having been tidally bound at the start of infall (though not necessarily now). Combining these observations with initial PMs of the Small Magellanic Cloud (SMC) suggests a new formation mechanism of the Magellanic Stream through the stripping of material from the SMC. However, large uncertainties remain in the exact mass of the LMC. We present a measurement of the systemic proper motions of the SMC from astrometry with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), covering a ~3 year baseline of 30 fields with background QSOs. We find these motions to be μW = −0.82 ± 0.06 mas/yr and μN = −1.23 ± 0.07 mas/yr. Combining these measurements with previous efforts in studying the Clouds will help constrain their interactions with each other and the MW, including the mass of the LMC and the MW, as well as provide new insight into the internal dynamics of the SMC.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2018 

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