Kim Griest

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What does extra LMC microlensing mean? 1. If events are in MW halo => - significant portion of DM - problem exists: What are they? -- stellar mass but can’t be stars (stars shine!) -- stellar remnant (white dwarfs, black holes) would need lots of early stars: no evidence for these (metal enrichment, background light, etc.) WD observed? -- primordial black holes? quark nuggets? 2. If events are LMC self lensing => - current LMC models wrong? - lens stars should be seen? 3. Contamination in MACHO dataset?
Much written on LMC self lensing since Sahu/Wu/Gould 1994 •MACHO used Gyuk, Dalal, <strong>Griest</strong> review of LMC models, valid in 2000, to predict 1-2 LMC self-lensing microlensing events. At that time no evidence of other stellar populations to do the self lensing. •HOW ABOUT RECENT EVIDENCE? •Zhao, Ibata, Lewis, & Irwin(2003) did 1300 2dF radial velocities: no evidence for any extra population over expected LMC and Galaxy Any new kinematically distinct population less than 1%. (rules out Evans & Kerrins 2000 fluffy stellar halo model)
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: LMC-23
Page 19 and 20: Contamination? • Contamination wa
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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