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New analysis of the proper motions of the Magellanic Clouds using HST/WFPC2

Published online by Cambridge University Press:  01 July 2008

Nitya Kallivayalil ,
Roeland P. van der Marel ,
Jay Anderson ,
Gurtina Besla  and
Charles Alcock
Nitya Kallivayalil
Affiliation:
Pappalardo Fellow, MIT Kavli Inst. for Astrophysics & Space Research, 70 Vassar Street, Cambridge, MA, 02139, USA; email: [email protected]
Roeland P. van der Marel
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Jay Anderson
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Gurtina Besla
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Charles Alcock
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
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Abstract

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In HST Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the Magellanic Clouds centered on background quasars. We used these data to determine the proper motions of the LMC and SMC to better than 5% and 15% respectively. The results had a number of unexpected implications for the Milky Way-LMC-SMC system. The implied three-dimensional velocities were larger than previously believed and close to the escape velocity in a standard 1012 M⊙ Milky Way dark halo, implying that the Clouds may be on their first passage. Also, the relative velocity between the LMC and SMC was larger than expected, leaving open the possibility that the Clouds may not be bound to each other. To further verify and refine our results we requested an additional epoch of data in Cycle 16 which is being executed with WFPC2/PC due to the failure of ACS. We present the results of an ongoing analysis of these WFPC2 data which indicate good consistency with the two-epoch results.

Keywords

astrometrygalaxies: interactionsgalaxies: kinematics and dynamicsMagellanic Clouds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S256: The Magellanic System: Stars, Gas, and Galaxies , July 2008 , pp. 93 - 98
Copyright
Copyright © International Astronomical Union 2009

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