PROPER MOTION OF THE LARGE MAGELLANIC CLOUD AND THE MASS OF THE GALAXY .1. OBSERVATIONAL RESULTS

We have measured the proper motion of the Large Magellanic Cloud (LMC) using 21 plates taken with the CTIO 4 m telescope and covering an epo ch span of 14 yr. The plates were centered on the globular cluster NGC 2257, lying on the northeast periphery of the Cloud. Proper motions w ere determined for 251 LMC members, chosen on the basis of the photome try of Stryker [ApJS, 55, 127 (1984)], using 92 galaxies as a referenc e frame. The measured mean absolute proper motion of the LMC stars in our region is mu(alpha) = O.120'' +/- 0.028'' century-1, mu(delta) = 0 .026'' +/- 0.027'' century-1. After correcting for the rotation of the LMC and the effects of solar motion, this proper motion combined with the radial velocity of the LMC implies a galactocentric coordinate ra dial velocity for the Cloud of 48 +/- 41 km s-1 and a total galactocen tric transverse velocity of 215 +/- 48 km s-1.