Kim Griest

What does it mean?
• Experimentally not clear: need more M31 work
(MEGA/POINT-AGAPE, etc); Supermacho on LMC.
From space can do parallax and (if approved) can answer
question of where lenses are; eventually SIM and do
astrometric microlensing. (Measure distance to 2 or 3
LMC lenses as 10 kpc to prove Macho DM. 3 or 4 at 50
kpc proves LMC self-lensing.) Need better modeling of
M31.
• Exciting current event: Spitzer IR satellite project
approved to get parallax (Gould et al). Currently following
an SMC event. Very likely to get distance.
• Theoretically: Macho DM consistent with
Omega_baryon = 0.04, but causes problems with star and
galaxy formation, or requires very exotic objects.