The Proper Motion of the Large Magellanic Cloud: A Reanalysis

Abstract

We have determined the proper motion (PM) of the Large Magellanic Cloud (LMC) relative to four background quasi-stellar objects, combining data from two previous studies made by our group, and new observations carried out in four epochs not included the original investigations. The new observations provided a significant increase in the time base and in the number of frames, relative to what was available in our previous studies. We have derived a total LMC PM of $μ$ = ($+2.0\pm$0.1) mas yr$^{-1}$, with a position angle of $θ$ = (62.4$\pm$3.1)$^\circ$. Our new values agree well with most results obtained by other authors, and we believe we have clarified the large discrepancy between previous results from our group. Using published values of the radial velocity for the center of the LMC, in combination with the transverse velocity vector derived from our measured PM, we have calculated the absolute space velocity of the LMC. This value, along with some assumptions regarding the mass distribution of the Galaxy, has in turn been used to calculate the mass of the Milky Way. Our measured PM also indicates that the LMC is not a member of a proposed stream of galaxies with similar orbits around our galaxy.