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Rotating haloes and the microlensing MACHO mass estimate
Authors:Geza Gyuk  & Evalyn Gates
Institution:S.I.S.A.A., via Beirut 2–4, 34014 Trieste, Italy,;Adler Planetarium, 1300 Lake Shore Drive, Chicago, IL 60605, USA,;Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637, USA
Abstract:We investigate the implications of a bulk rotational component of the Galactic halo velocity distribution for MACHO mass estimates. We find that for a rotating halo to yield a MACHO mass estimate significantly below that of the standard spherical case, its microlensing must be highly concentrated close to the Sun. We examine two classes of models fitting this criterion: a highly flattened 1/ r 2 halo, and a spheroid-like population the density of which falls off as 1/ r 3.5. The highly flattened 1/ r 2 models can decrease the implied average MACHO mass only marginally, and the spheroid models not at all. Generally, rotational models cannot bring the MACHO mass implied by the current microlensing data down to the substellar range.
Keywords:Galaxy: halo  dark matter  gravitational lensing  
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