## 4. Multi-component model of the LMCWe model the LMC to contain several stellar populations, each associated with a different velocity dispersion which has evolved according to Eq. 9. We describe each of the ten components of our model by an ellipsoidal density profile up to a cut-off radius kpc
(Aubourg et al. 1999). The multi-component model based on these
profiles is self-consistent in the sense that it satisfies Poisson
equation and results in a flat rotation curve with the desired
of 80 km s For a given distribution of objects, one can compute the total self-lensing optical depth and the event rate . Both quantities are integrated on all deflectors and sources, considering that only main sequence stars brighter than and red giants can be potential sources, since they are the only objects bright enough to be visible in microlensing surveys. The computation of requires an estimate of the relative transverse velocity of deflector and source, for which we have assumed an horizontal velocity dispersion equal to the vertical one predicted by the model. Details of this computation can be found in (Aubourg et al. 1999). For the model described above, one obtains
and
yr Another relevant prediction of the model is the distribution of event durations, . Fig. 3 illustrates this prediction for our model, along with the distribution of observed MACHO events.
Our model thus reproduces both the total observed optical depth
towards the LMC and the observed event duration
distribution, while complying with the velocity dispersion
measurements. A self-lensing interpretation of © European Southern Observatory (ESO) 1999 Online publication: October 14, 1999 |