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Paper   IPM / P / 7923
School of Physics
  Title:   Galactic MACHO Budget: Problems and Possible Solution with the Abundant Brown Dwarfs
  Author(s):  S. Rahvar
  Status:   In Proceedings
  Proceeding: Proceedings of XI Regional Conference on Mathematical Physics, 3-6 May 2004, p12-14, Tehran, Iran
  Year:  2004
  Pages:   12-14
  Supported by:  IPM
The gravitational microlensing experiments in the direction of Large Magellanic Cloud (LMC) predict a large amount of white dwarfs ( ∼ 20 %) filling the galactic halo. The main contradiction of this result with the other astrophysical observations is (i) the predicted white dwarfs are not observed at the galactic halo and (ii) the evidence of the existence of white dwarfs is the heavy metals whose signature have not been detected. To interpret the microlensing results and resolving the mentioned problems, we use the hypothesis of spatially varying mass function of MACHOs, proposed by Kerins and Evans(hereafter KE). However the KE model is npt compatible with the duration distribution of the events. To have a better parameters for the model, we do a likelihood analysis and show that in contrast to the abundant brown dwarfs of the halo, heavy MACHOs reveal themselves frequently as the microlensing events.

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