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| Paper: |
Proper Motions of Dwarf Spheroidal Galaxies |
| Volume: |
92, Formation of the Galactic Halo. . . . Inside and Out |
| Page: |
532 |
| Authors: |
Schweitzer, Andrea E.; Cudworth, Kyle M. |
| Abstract: |
We have measured an absolute proper motion for the Sculptor dwarf spheroidal galaxy, a companion to the Milky Way at a distance of nearly 80 kpc. This result is based on 26 plates taken over the course of more than half a century from four different telescopes, with the zero point of the absolute proper motion set by several background galaxies. Although our measured motion is less than twice its uncertainty, the direction of Sculptor's motion is significant because it rules out motion along the Magellanic Stream but allows motion (within 3sigma ) toward the Fornax dwarf spheroidal galaxy. A new proper motion study is also in progress for the Ursa Minor dSph using plates from the Palomar 200-inch taken in the 1950's as the first epoch and more recent plates from the Kitt Peak 4-m. Because of this much superior plate material and the much larger area covered, we anticipate significantly higher precision for the absolute proper motion of UMi than for Scl. As of this conference we have the reductions to the point of deriving very preliminary membership probabilities for stars in UMi, but we are not yet ready to derive an absolute proper motion until we can deal with some remaining systematic problems in the measurements or reductions. |
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