Proper Motion Study of the Magellanic Clouds using SPM material
  Absolute proper motions are determined for stars and galaxies to V=17.5 over
a 450 square-degree area that encloses both Magellanic Clouds. The proper
motions are based on photographic and CCD observations of the Yale/San Juan
Southern Proper Motion program, which span over a baseline of 40 years.
Multiple, local relative proper motion measures are 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 of 1.4 million
objects is used to derive the mean absolute proper motions of the Large
Magellanic Cloud and the Small Magellanic Cloud;
$(\mu_\alpha\cos\delta,\mu_\delta)_{LMC}=(1.89,+0.39)\pm (0.27,0.27)\;\;\{mas
yr}^{-1}$ and $(\mu_\alpha\cos\delta,\mu_\delta)_{SMC}=(0.98,-1.01)\pm
(0.30,0.29)\;\;\{mas yr}^{-1}$. These mean motions are based on best-measured
samples of 3822 LMC stars and 964 SMC stars. A dominant portion (0.25 mas
yr$^{-1}$) of the formal errors is due to the estimated uncertainty in the
inertial system of the Hipparcos Catalog stars used to anchor the bright end of
our proper motion measures. A more precise determination can be made for the
proper motion of the SMC {\it relative} to the LMC;
$(\mu_{\alpha\cos\delta},\mu_\delta)_{SMC-LMC} = (-0.91,-1.49) \pm
(0.16,0.15)\;\;\{mas yr}^{-1}$. This differential value is combined with
measurements of the proper motion of the LMC taken from the literature to
produce new absolute proper-motion determinations for the SMC, as well as an
estimate of the total velocity difference of the two clouds to within $\pm$54
kms$^{-1}$.
