PROPER MOTION OF THE MAGELLANIC CLOUDS USING SPM

Absolute proper motions are determined for stars and galaxies to V = 17.5 over a 450 square-degree area that includes the Magellanic Clouds, using photographic and CCD observations of the Yale/San Juan Southern Proper Motion program. Multiple, local relative proper motion measures were combined in an overlap solution using photometrically selected galactic disk stars to define a global relative system that is then transformed to absolute using external galaxies and Hipparcos stars to tie into the ICRS. The resulting catalog is used to derive the mean absolute proper motions of the Magellanic Clouds: (mu(alpha) cos delta, mu(delta))(LMC) = (+1.88, +0.37) +/- (0.27, 0.27) mas yr(-1) and (mu(alpha) cos delta, mu(delta))(SMC) = (+1.05, 1.03) +/- (0.30, 0.29) mas yr(-1), based on best-measured samples of 3822 LMC stars and 964 SMC stars. A dominant portion of the formal errors is due to the estimated uncertainty in the inertial system of the Hipparcos Catalog. A more precise determination was made for the proper motion of the SMC relative to the LMC; (mu(alpha) cos delta, mu(delta))(SMC-LMC) = (-0.91, -1.49) +/- (0.16, 0.15) mas yr(-1). This differential value is used to estimate of the total velocity difference of the two clouds to within +/- 54 km s(-1). The absolute proper motion results are consistent with the Clouds' orbits being marginally bound to the Milky Way, albeit on an elongated orbit.