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Session 65 - New Views of the Magellanic Clouds - II.
Oral session, Wednesday, June 12
Historical Society,

[65.04] The Mass of the Large Magellanic Cloud

W. E. Kunkel (OCIW), S. Demers (U. de Montréal), M. J. Irwin (RGO)

Our ongoing survey for cool carbon stars in the outer halo of the Large and Small Magellanic Clouds (LMC, SMC) has resulted in the discovery of several hundred previously unidentified carbon stars. Spectra and radial velocities were obtained, at a resolution of 2.5 Åat the du Pont telescope. This dataset provides an excellent kinematic probe of the dynamics of the LMC-SMC-Galaxy interaction. In this presentation we will discuss the results we have obtained for the rotation curve of the Large Magellanic Cloud out to a radius of 10 degrees.

Our main conclusions are that: \beginitemize \item beyond 5 degrees the rotation amplitude declines slowly, with a maximum value obtained for radius of 4--5 degrees; \item there are strong indications of perturbations in the velocity field in the inner parts of the SW of the LMC and the outer regions to the NE; \item the velocity dispersion with respect to a circular rotation curve is roughly constant as a function of radius; \item the kinematic line of nodes is approximately constant for all toroidal zones between 4--8 degrees radius for transverse velocities in the range 150--300 km/s. \enditemize

Assuming circular rotation and an inclination between 27--33 degrees, implies that the total mass in the LMC out to a radius of 10 degrees is \approx 6 \times 10^9M_ødot and the majority of this mass is located within the inner 5 degrees. This suggests that the mass:to:light ratio of the LMC is \approx4 and that the LMC does not possess a massive dark halo.

Program listing for Wednesday