Microlensing by the Halo MACHOs with Spatially Varying Mass Function

Abstract

The main aim of microlensing experiments is to evaluate the mean mass of massive compact halo objects (MACHOs) and the mass fraction of the Galactic halo made by this type of dark matter. Statistical analysis shows that by considering a Dirac-Delta mass function (MF) for the MACHOs, their mean mass is about that of a white dwarf star. This result is, however, in discrepancy with other observations such as those of non-observed expected white dwarfs in the Galactic halo which give rise to metal abundance, polluting the interstellar medium by their evolution. Here we use the hypothesis of the spatially varying MF of MACHOs, proposed by Kerins and Evans to interpret microlensing events. In this model, massive lenses with a lower population contribute to the microlensing events more frequently than do dominant brown dwarfs. This effect causes the mean mass of the observed lenses to be larger than the mean mass of all the lenses. A likelihood analysis is performed to find the best parameters of the spatially varying MF that are compatible with the duration distribution of Large Magellanic Cloud microlensing candidates of the MACHO experiment.

arXiv comment7 pages, 4 figure

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Cited by in corpus (5)

• Photometric Confirmation of MACHO Large Magellanic Cloud Microlensing Events
• The contribution of red dwarfs and white dwarfs to the halo dark matter
• The contribution of Oxygen-Neon white dwarfs to the MACHO content of the Galactic Halo
• Identification of the Microlens in Event MACHO-LMC-20
• Constraining Galactic Models Through Parallax and Astrometry of Microlensing Events