Kim Griest

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• Gallart, Stetson, Hardy, Pont, & Zinn (2004), search for a stellar population in a deep surface brightness CMD, and found no evidence for any stellar halo • However, Minniti, et al (2003), and Alves (2004) found RVs for 43 RR Lyaes and discovered an old and hot stellar halo! But they say it is too small to account for all the extra microlensing • But the structure of the LMC is being questioned: van der Marel,et al (2002) says the LMC disk is not circular, but Nikolaev, et al. (2004) disagree, saying it is warped. Both say it does not probably affect self lensing much (e.g. Mancinit etal 2003 agree), but it does show the LMC is still not well understood. • Summary: no clear answer yet
Contamination? • Contamination was studied by MACHO; selection criteria: A: 13 events, tight cuts, less contamination., lower effs B: 17 events, loose cuts, more contam., higher effs tau(A) =1.1e-7, tau(B)=1.3e-7. 17% difference estimates contamination systematics • But Belokurov, Evans, & LeDu used neural net to reanalyze MACHO LMC data. Say data set is badly contaminated; find only 6 or 7 microlensing events => tau much smaller => no need for either Machos in dark halo or extra LMC self lensing!
Page 1 and 2: Microlensing and Dark Matter August
Page 4 and 5: Executive Summary • Basic Result:
Page 7: LMC in neutral H looks like a face-
Page 10: •Masses 0.1 - 1.0 Msun preferred
Page 13 and 14: The number of non-Macho events is p
Page 15 and 16: LMC-23
Page 17: Much written on LMC self lensing si
Page 21 and 22: What do to? Other experiments!
Page 24 and 25: Combined MACHO and EROS limits on s
Page 26 and 27: LMC Limits on Macho Dark Matter •
Page 28 and 29: MEGA: M31 Microlensing Found 4 even
Page 30 and 31: Other M31 results • WeCAPP (Wende
Page 32 and 33: BULGE Microlensing: three collabora
Page 35 and 36: 34 candidate events probably from t
Page 37: Conclusion • The mystery of LMC/M

Kim Griest

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