Several collaborations (Alcock et al. 1993, Aubourg et al. 1993) are searching for galactic dark matter through the use of gravitational microlensing (Paczynski 1986) towards the Magellanic Clouds. Events have been observed, for which location and mass cannot be determined independently. The current results do not yet yield a coherent explanation: half of the halo of the Milky Way in 0.5 objects (Alcock et al. 1997) would require a puzzling star formation history, whereas traditional models of the LMC do not predict a self-lensing optical depth high enough to account for all the observed events (Gould 1995). The only events with additional information all seem to be located in the Clouds themselves (Bennett et al. 1996, Palanque-Delabrouille et al. 1998, Afonso et al. 1999), which makes it worthwhile to re-examine the experimental constraints on the Clouds kinematics and explore more thoroughly models of the LMC . After reviewing the observational constraints on the LMC kinematics (Sect. 1), we show, in Sect. 2, the existence of an age bias: the stars used to derive these constraints are on average both younger and slower than the majority of the LMC objects. We then use a Monte Carlo simulation to show that a maximum velocity dispersion of 60 km s-1 reproduces the kinematic observations (Sect. 3) and the microlensing results (Sect. 4).
© European Southern Observatory (ESO) 1999
Online publication: October 14, 1999