Are there Machos in the Halo

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Are there Machos in the Halo?

• Irvine
• March 2007
• Kim Griest, UCSD

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• Surveys monitor millions of stars for years to
  find rare lensing events
• Bulge gt stars, remnants, planets, etc.
• LMC/SMC/M31 gt DM

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Test of systematic error due to
contamination, selection bias compare A B
criteria Criteria A tighter cuts, with less
contamination Criteria B looser cuts, with
more contamination
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The number of non-Macho events is predicted to be
much smaller than the 13-17 events observed
(using standard LMC and Milky Way stellar
populations.)
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• Masses 0.1 - 1.0 Msun preferred
• Halo fraction 8 - 40 preferred
• Total mass in Machos 8-10 1010 Msun (MW
  disk6 1010 Msun, and MW halo has 4-6 1011
  Msun)
• Optical depth 1.20.4-0.3 10-7

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• Main conclusion Machos as main component of
  Dark Matter are ruled out
• But found significant extra microlensing

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But these results need correcting

• Recently EROS (Glicenstein 2004) found that event
  LMC-23 bumped again after 7 years gt variable
  star, not lensing.
• LMC-23 contributed 8 of optical depth (and halo
  fraction) (6 for set B), so all our optical
  depths and halo fractions should be reduced at
  least 8.
• gt best f 18.5, and tau1.1 10-7 (Griest
  Thomas), or f16, tau1 10-7 (Bennett)
• More worrying are there more events like this?

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LMC-23
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What does extra LMC microlensing mean?
1. If events are in MW halo gt - significant
portion of DM - problem exists What are
they? -- stellar mass but cant 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? NT
solitons? 2. If events are LMC self lensing gt
- current LMC models wrong? -
lens stars should be seen? 3. Contamination in
MACHO dataset?
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The number of non-Macho events is predicted to be
much smaller than the 13-17 events observed
(using standard LMC and Milky Way stellar
populations.)
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LMC in neutral H looks like a face-on disk.
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Much written on LMC self lensing since
Sahu/Wu/Gould 1994

• MACHO used Gyuk, Dalal, Griest 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)

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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

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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 gt tau much smaller gt no need for either
  Machos in dark halo or extra LMC self lensing!

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Wrong!

• Found events by running only on our selected
  events, but calculated efficiencies without
  including effect of our selection gt badly
  miscalculated efficiencies.
• Analyzed only 22000 lightcurves out of 11.9
  million
• Also used very weak statistics gt much lower eff,
  and many false positives (2 out of 22000) gt
  probably would not even work if applied to all
  11.9 million lightcurves
• Rejected good microlensing, misidentified SN
• Conclusion BEL analysis is meaningless neural
  nets may be useful, but have yet to be applied
  correctly. Contamination possible, but certainly
  not shown yet. Results of MACHO LMC5.7 stand
  after small correction for LMC-23.

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What do to? Other experiments!
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EROS collaboration 4 events in 50 LMC fields
and 4 events in 10 SMC fields Interpreted as
limit on Halo dark matter
LMC Events
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LMC Limits on Macho Dark Matter

• MACHO plus original EROS Objects with 10-7 lt m lt
  10-3 Msun make up less than 25 of DM. Objects
  with 3.5 10-7 lt m lt 4.5 10-5 make up less than
  10 of DM
• EROS reanalysis (Tisserand et al. 2006) took 7
  million out of 33 million brightest stars
  assumed no blending found no events gt tault0.36
  10-7, flt 7 (95CL). (CONFLICTS WITH MACHO
  RESULT)

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• M31 microlensing is the new frontier (and site of
  new controversies!)
• At least 4 groups have returned results (but
  situation not clarified!)
• Key idea was to use M31 inclination and near/far
  asymmetry if Macho halo, many more events
  should appear on far side of M31

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De Jong, et al. AA, 446,855, 2006
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MEGA M31 Microlensing Found 4
events Measure Macho halo fraction f0.29
0.30 -0.13 .01lt m lt 1 Msun gt M31 halo DM
consistent With MACHO LMC result!
BUT POINT-AGAPE M31 have 3 events say flt.25
(.6) for .0001ltmlt.1 (.1ltmlt1 Msun)
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More recently reversal!

• POINT/AGAPE has 6 events model M31 say more
  than self-lensing halo fraction f gt20 for .5
  ltmlt1 Msun, or fgt8 for m.01Msun (95 CL) plus
  likely binary event on far side. (Calachi Novati,
  et al. AA, 2005)
• MEGA has 14 events, still large asymmetry, but
  more careful modeling says asymmetry may be from
  extinction limit flt30, best fit f0 or f10
  depending on model now say might be consistent
  with self-lensing. (de Jong, et al. AA 446, 855
  (2006)
• Separate POINT/AGAPE search has 5 good events 4
  on far side, 1 on near no conclusions
• Difference may depend on bulge M/L4 or 8?
• Also new reanalysis of MEGA (Ingrosso et al. AA
  Oct 2006) says only extreme M31 models compatible
  with f0.

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Calachi Novati, et al. AA 443 911 (2005)
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Other M31 results

• WeCAPP (Wendelstein Calar Alto Pixellensing
  project) found 2 events toward M31. Say favor
  M31 halo lenses, but evidence very weak (in my
  opinion).
• Nainital group found one M31 event (on far side),
  no conclusions.

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New Result Spitzer Infrared satellite parallax

• Cant tell distance to invisible lens, but if
  could view same event simultaneously far from
  Earth, then you could
• Combined groundSpitzer of OGLE-2005-SMC-1, finds
  vproj 230 km/s

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New Result Spitzer Infrared satellite parallax

• Combined groundSpitzer of OGLE-2005-SMC-1, finds
  vproj 230 km/s
• Disk lens gt 50km/s, Halo lens gt 300 km/s, SMC
  lens gt 2000 km/s
• Likelihood ratio Halo/SMC 20!
• BUT mass is wrong to be MACHO event! This binary
  lens seems to have mass 7 and 3 Msun gt black
  holes! MACHO wanted 1/2 Msun lenses

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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 can 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.
• Spitzer IR satellite project proposal to get
  more parallax events (Gould et al). Hope to get
  LMC event.
• Theoretically Macho DM consistent with
  Omega_baryon 0.04, but causes
  problems with star and galaxy formation, or
  requires very exotic objects.

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Executive Summary

• Basic Result Searches done and show bulk of DM
  cannot be in compact objects with masses between
  Mars mass and 100 Msun
• Conflicting results on whether ANY halo DM can
  exist in this form 2 collaborations say yes, 2
  say no, and new Spitzer SMC measurement says yes
• IF measurable amount of Macho halo DM exists, it
  would be a major new component of MW (and M31) gt
  important consequences for galaxy formation and
  evolution

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Conclusion

• The mystery of LMC/M31 microlensing is still
  unsolved, and more work is needed
• If you want an inventory of all compact objects,
  independent of luminosity, microlensing is the
  way to go, i.e. Microlensing has a bright future
  for finding dark objects

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• BULGE Microlensing
• Three collaborations
• returned results OGLE,
• EROS, MACHO.
• MACHO results
• 50 million stars over 7 year
• gt450 events, 60 on clump giants (less blended)
• 40 binary events, parallax, extended source,
  lensing of variable stars, etc.

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Location of all 500 MACHO events. (b,l)(0,0)
is Galactic center Many of these Are blended.
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Microlensing lightcurves have well specified
shapes depending on 3 parameters Maximum
magnification Amax, event duration that, and
time of peak. Blended lightcurves look very
similar, but have different values for Amax and
that
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Are events all microlensing? Microlensing is
uniformly distributed in impact parameter, umin
1/Amax K-S test shows probability of 2.5 for
these 258 events. Deviation is from blending.
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Microlensing should be randomly distributed in
Color-Magnitude
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Select clump giants from color-magnitude diagram
62 events
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For 60 clump giant events probability is 81. So
these are unblended microlensing
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62 Clump giant events. Circle size is
proportional to event duration.
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• Optical depth 2.18 .45-.38
• 10-6
• Agrees with models (e.g. Gould and Han 1.63 10-6)
• Also agrees with EROS and OGLE gt no more bulge
  problem

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34 candidate events probably from the recently
discovered Sagittarius dwarf galaxy
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Planet Microlensing
MPF
Source Star
Planet
Magnification
Lens Star
Lensed Images
Magnification
Planets with Gravitational microlensing (Mao and
Paczynski, 1991). The foreground lens star
distorts and magnifies images of the background
star for months, and lensing planet modifies
light curve for 1 day.
(Slides c/o Dave Bennett and Scot Gaudi)
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Extraction of Exoplanet Signal
Time-series photometry is combined to uncover
light curves of background source stars being
lensed by foreground stars in the disk and bulge.
Twice Earth Earth Half Earth No Planet
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3.5
Magnification by stellar lens
3
Magnification
2.5
Magnification
2.5
Deviation Due to Planet
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Offset from peak gives projected separation
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1.5
9.2
9.4
9.6
9.8
-20
-10
0
10
20
Days
Days
Detailed fitting to the photometry yields the
parameters of the detected planets.
Planets are revealed as short-duration deviations
from the smooth, symmetric magnification of the
source due to the primary star.
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Results Limits on Cool Jupiters

• Analysis of PLANET data
• 1995-1999
• 43 Events
• No viable detections
• Quantified efficiencies
• Upper limits on G-M dwarfs
• lt33 have cool Jupiters (MMJ with 1.5-4AU)
• lt50 have Jupiter analogs (MMJ with a5.2 AU)

(Albrow et al 2001, Gaudi et al 2002)
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First Planet DetectionOGLE-2004-BLG-235/MOA-2004-
BLG-53

• Jointly discovered by OGLE and MOA
• Caustic-crossing event
• Unambiguous
• Additional constraints
• Primary
• Planet

(Bond et al 2004)
The technique works!
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Second Planet DetectionOGLE-2005-BLG-071

• Jointly discovered by OGLE ?FUN (also PLANET
  MOA)
• High-magnification event
• Very high S/N detection
• Discovered real-time
• HST dataLCMCMCBayesian
• May yield mass measurement
• Primary
• Planet

(Udalski et al 2005, Gaudi et al, in prep)
Cool Jupiters, while uncommon, are not rare
(frequency 5-10)
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Third Planet DetectionOGLE-2005-BLG-390

• Discovered by PLANET (also OGLE MOA)
• Classical planetary event
• Giant source resolved
• Additional constraints
• Very low-mass planet
• Primary
• Planet
• RV

(Beaulieu et al 2006)
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Fourth Planet DetectionOGLE-2005-BLG-169

• Very High-Magnification Event
• Maximum Magnification 700!

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Fourth Planet DetectionOGLE-2005-BLG-169

• Very High-Magnification Event
• Maximum Magnification 700!
• Dense coverage on falling side of peak
• Sampling of 10 seconds
• Low-amplitude anomaly
• Highly significant
• Present in multiple datasets
• Present in different reductions
• Not seen in reference stars
• Not correlated with seeing, background, etc.
• Planetary fits yield mass ratios 10-6 -10-5
• Primary
• Planet

gt Cool Neptune-mass planets are common
(frequency 40)
f .37.3-.21, and fgt16 (90CL) (Gould et al
astroph0306327)
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Current Inventory of Planets

• RV Surveys
• 164 Planets
• Transit Surveys
• 6 Planets
• Microlensing Surveys
• 4 Planets
• Pulsar Timing
• 4 Planets

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Whats Next?

• Current setup (alert/follow-up) saturated
• Nearly all of the useable bulge monitored
• Many events cannot be monitored
• Monitoring one event at a time too inefficient

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MPF Science Team
Mission Parameters
PI D. Bennett (Notre Dame) Science Team J.
Anderson (Rice), J.-P. Beaulieu (IAP), I. Bond
(Massey), M. Brown (Caltech), E. Cheng (CcA), K.
Cook (LLNL), S. Friedman (STScI), P. Garnavich
(Notre Dame), S. Gaudi (CfA), R. Gilliland
(STScI), A. Gould (Ohio State), K. Griest (UCSD),
J. Jenkins (Seti Inst.), R. Kimble (GSFC), D. Lin
(UCSC), J. Lunine (Arizona), J. Mather (GSFC),
D. Minniti (Catolica), B. Paczynski (Princeton),
S. Peale (UCSB), B. Rauscher (GSFC), M. Rich
(UCLA), K. Sahu (STScI), M. Shao (JPL), J.
Schneider (Paris Obs.), A. Udalski (Warsaw), N.
Woolf (Arizona) and P. Yock (Auckland)

• 1.1 meter aperture
• 0.65 deg2 FOV
• 35 2K by 2K HgCdTd detectors
• 3 IR bands (600-1700 nm)
• Geosynchronus orbit
• Monitor 200,000,000 bulge stars in 4 fields for 4
  years
• 400M cost (Discovery)

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Planet Detection Sensitivity

• Sensitivity to all Solar System-like planets
• Except for Mercury Pluto
• most sensitive technique for a ? 1 AU
• Good sensitivity to outer habitable zone
  (Mars-like orbits) where detection by TPF is
  easiest
• Mass sensitivity is 1000 ? better than vrad
• Assumes ??2 ? 80 detection threshold
• Can find moons and free planets

Updated from Bennett Rhie (2002) ApJ 574, 985
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Predicted Discoveries

• Expected MPF planet detections if each lens
  system has a solar system analog planetary
  system with the same star-planet separations and
  mass ratios as our own planetary system.

The number of expected MPF planet discoveries as
a function of star-planet mass ratio.
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Conclusion

• The mystery of LMC/M31 microlensing is still
  unsolved, and more work is needed
• If you want an inventory of all compact objects,
  independent of luminosity, microlensing is the
  way to go, i.e. Microlensing has a bright future
  for finding dark objects

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Detection Limits
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Lensing Substructure
N. Dalal (Institute for Advanced Study) C.S.
Kochanek (Center for Astrophysics) ApJ 572 25
(2002) astro-ph/0302036
Moore et al. (1999)

• Outline
• Flux anomalies in GL systems
• a. what are they?
• b. evidence for substructure?
• 2. Comparison with CDM predictions
• 3. Implications future directions

Satellites Tidal Streams 2003
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CDM Substructure

• CDM models predict much more substructure than is
  seen in luminous satellites (Klypin et al. 1999,
  Moore et al. 1999).
• This satellite excess has been viewed as a
  problem for CDM, leading to warm dark matter,
  etc., or may indicate that feedback processes
  suppress star formation in low mass halos

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Strong galaxy lensing

• Deflection of light by foreground galaxy causes
  multiple imaging of background source

Q2237030
Simple mass models (e.g. isothermal ellipsoids)
can account for image positions, but usually FAIL
to explain image fluxes in quad lenses! More
complex models (e.g. boxy or disky) also fail to
fit image fluxes. These so-called flux
anomalies are nearly ubiquitous among quads.
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Flux anomalies - examples

• fluxes of close images obey asymptotic
  relationships for smooth mass models (e.g.
  Schneider et al. 1992)

fold relation
cusp relation
B2045265 (Fassnacht et al. 1999)
B1555375 (Marlow et al. 1999)
and plenty more examples
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laundry list of possible causes

• propagation effects (e.g. scintillation,
  absorption)
• variability
• wrong smooth model for galaxy
• stellar microlensing
• aliens tricking us
• massive (gt106 Msun) substructure

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Substructure lensing

• naturally explains frequency independence
  (equivalence principle)
• long variation timescale millennia
• predicts observed parity dependence for both
  microlensing (Schechter Wambsganss 2002) and
  subhalo lensing

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How Much Substructure?

• approximate Bayesian analysis finds 2 of
  surface density in substructure best fits data

for bsat2.5 mas, Msat2 107 Msun
Problem elliptical galaxies are not clumpy (e.g.
Conselice 2003) and observed substructure (e.g.
globular clusters, luminous satellite galaxies)
not abundant enough to account for incidence of
anomalies
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Conclusions

• Lensing is a great way to see dark objects
• In future lensing will increase in importance
  SIM, LSST, Supermacho, SNAP, MPF, and many other
  projects

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BULGE Microlensing three collaborations returned
results OGLE, EROS, MACHO
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Microlensing towards bulge

• 50 million stars over 7 year
• gt450 events, 60 on clump giants (less blended)
• 40 binary events, parallax, extended source,
  lensing of variable stars, etc.
• Optical depth 2.18 .45-.38 10-6, agrees with
  models (e.g. Gould and Han 1.63 10-6)
• Also found optical depth as a function of (b,l)
  and gradient in optical depth

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MACHO Collaboration (2000)

• Monitored 11.9 million stars for 5.7 years
• Found 13-17 events (depending on selection
  criteria)
• Careful efficiency analysis including blending
• Removed 8 Supernova behind LMC (contaminants)
• Distribution in space, CMD, Amax, consistent with
  microlensing interpretation
• Likelihood analysis to measure Macho DM, plus
  events in disk, LMC, etc.

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Low-Mass Planets Discovered by Microlensing

• 2 of the 4 planets that have been discovered by
  microlensing have masses lt 20M?

Known Sub-Neptune Mass Planets
A 5.5 M? planet discovered by microlensing
OGLE-2005-BLG-390Lb. This is the light curve of
the lowest mass planet yet detected in orbit
around a normal star by any method.
Ground-based microlensing is currently the most
powerful technique for the detection of low-mass
planets orbiting normal stars, but there are
limitations on the sensitivity that can be
achieved from the ground.
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The first planet to be discovered by
microlensing OGLE 2003-BLG-233/ MOA 2003-BLG-53
q.0039. Likely star mass of 0.4 Msun,
likely Planet mass of 1.5 M_jupiter. Second
planet found in June (OGLE-2005-BLG-071). 0.05 lt
m/M_jupiter lt 4, at distance of several kpc
very high S/N
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Are lenses DM in Galaxy or LMC Self lensing?
If events are in MW halo gt - significant
portion of DM - problem exists What are
they? -- stellar mass but cant 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.) If events are LMC self
lensing gt - current LMC models are wrong -
why are the lens stars not seen?
Lots of tests done none conclusive yet
Other lensing info?
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New Planet Detection!OGLE-2005-BLG-169

• Very High-Magnification Event
• Maximum Magnification 700!
• Dense coverage on falling side of peak
• Sampling of 10 seconds

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New Planet Detection!OGLE-2005-BLG-169

• Very High-Magnification Event
• Maximum Magnification 700!
• Dense coverage on falling side of peak
• Sampling of 10 seconds
• Low-amplitude anomaly
• Highly significant
• Present in multiple datasets
• Present in different reductions
• Not seen in reference stars
• Not correlated with seeing, background, etc.

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De Jong, et al. AA, 2006 (MEGA)
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Combined MACHO and EROS limits on short duration
small mass objects
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Limits vary according to Milky Way halo model
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