No need for MACHOs in the halo

Evalyn I. Gates, Geza Gyuk, Gilbert P. Holder, Michael S. Turner

Research output: Contribution to journalArticlepeer-review


One interpretation of the more than dozen microlensing events seen in the direction of the LMC is a halo population of 0.5 M MACHOs that accounts for about half of the mass of the Galaxy. Such an interpretation is not without its problems, and we show that LMC microlensing can be explained by a combination of dark components of the thick disk and spheroid in a viable and detailed model of the Galaxy. In our models, the total mass within 50 kpc is ∼1011 M, about 60% of the value based on halo MACHO models, and the estimate for the lens mass is lower, 0.3 M versus 0.5 M. The chemical evolution problems associated with the MACHO progenitors are not resolved. However, since the MACHO distribution does not trace the l/r2 dark halo, which extends significantly beyond 50 kpc, the total baryon mass fraction of the Galaxy is reduced considerably, which lessens the problem.

Original languageEnglish (US)
Pages (from-to)L145-L148
JournalAstrophysical Journal
Issue number2 PART II
StatePublished - 1998
Externally publishedYes


  • Dark matter
  • Galaxy: halo
  • Galaxy: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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