Dark Matter in the Galactic Bulge: A Microlensing Point of View
Abstract
Microlensing is one of the most promising technique to probe the density of dark matter in the Galactic Bulge. We review briefly the history of microlensing and comment on the discovery of high optical depth in the direction of the Bulge. This optical depth is several times larger than the first theoretical predictions. We will show that some of the discrepancy can be resolved by taking into account the effect of self amplification of stars into the Galactic Bar. We will also explain that the optical depth is contaminated with the contribution of faint unresolved stars. However, we emphasize that a category of sources, the bulge giants are bright enough to escape the bias due to unresolved sources. Finally we show that even if self amplification in the bar is taken into account, the optical depth to giants is hard to reproduce. We conclude by saying that in the near future this excess in the bulge optical depth should be clarified and measured with good accuracy. In particular good progress should be made when the analyze of the last observations of Bulge giants will be completed by the MACHO group. The future implementation of the image subtraction technique in the data pipelines should also help to overcome the bias in the measurement of the optical depth to turnoff stars.
Keywords
Dark Matter Impact Parameter Light Curve Optical Depth Acta AstronPreview
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