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Paper: Lensing Surveys of the Milky Way
Volume: 317, Milky Way Surveys: The Structure and Evolution of Our Galaxy
Page: 165
Authors: Evans, N.W.
Abstract: At just 10 years of age, microlensing is the youngest technique in Galactic astronomy, but it uniquely has the power to probe directly the mass distribution rather than the light distribution. Microlensing has already made fundamental contributions to our knowledge of the Galaxy, for example, by demonstrating that the interior of the Milky Way is overwhelmingly baryon-dominated and by showing that dark haloes are not made up of failed stars or red dwarfs. Large-scale microlensing surveys of the Milky Way provide powerful constraints on the mass distribution in the bulge, bar and the spiral arms. As is natural in such a young subject, there are a number of perplexing puzzles. First, there is substantial variation in the optical depth results reported by the differing microlensing surveys of the inner Galaxy. Secondly, almost all the surveys find that the optical depth towards the Galactic bulge is much large than even a barred, baryon-dominated Galaxy can explain. Thirdly, the microlensing results towards the Large Magellanic Cloud permit no straightforward explanation. All this suggests that systematic effects in the experiments are still not fully understood. The role of neural networks in providing automatic lightcurve classification is discussed and the results of re-processing some microlensing events is given.
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