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

Nitya Kallivayalil, Roeland P. Van Der Marel, Jay Anderson, Gurtina Besla, Charles Alcock

Research output: Contribution to journalArticlepeer-review


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 10 12 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.

Original languageEnglish (US)
Pages (from-to)93-98
Number of pages6
JournalProceedings of the International Astronomical Union
Issue numberS256
StatePublished - Jul 2008


  • Astrometry
  • Galaxies: interactions
  • Galaxies: kinematics and dynamics
  • Magellanic Clouds

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science


Dive into the research topics of 'New analysis of the proper motions of the Magellanic Clouds using HST/WFPC2'. Together they form a unique fingerprint.

Cite this