gravitational lensing: how to see the dark j. e. bjorkman university of toledo department of physics...
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Gravitational Lensing: Gravitational Lensing: How to See the DarkHow to See the Dark
J. E. BjorkmanUniversity of Toledo
Department of Physics & Astronomy
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The Dark Between the LightThe Dark Between the Light
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Dark MatterDark Matter
How do we know its there?Answer: It affects the motion of everything
we can see.– Cluster Simulation– Rotation Velocities
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Galactic Rotation CurvesGalactic Rotation Curves
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Missing Mass in our GalaxyMissing Mass in our Galaxy
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What is the Dark?What is the Dark? MACHOs (Massive Compact Halo Objects)
– low mass stars - "brown dwarves"– "almost" stars (planets, e.g. Jupiters)– black holes of less than solar mass– The VW graveyard
WIMPs (Weakly Interacting Massive Particles)– heavy neutrinos (10 to 1000 GeV)– new particles predicted by Supersymmetry - 'neutralinos' – exotic particles – e.g. axions (particles with mass < 0.1 eV)
Modified Gravity - on galactic scales.
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Where is the Dark?Where is the Dark?
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Gravity Bends Light (Einstien)Gravity Bends Light (Einstien)
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Gravitational LensesGravitational Lenses
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Einstein tells Eddington gravity bends starlight.
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Eclipse AstrometryEclipse AstrometryHow do we know the stars moved?
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Relativity VerifiedRelativity Verified
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Discovery of a Gravitational LensDiscovery of a Gravitational Lens
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Galaxies as LensesGalaxies as Lenses
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A Lensing SimulationA Lensing Simulation
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A Lens GalleryA Lens Gallery
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Galaxy Clusters as LensesGalaxy Clusters as Lenses
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Measuring the DarkMeasuring the Dark
0.5% of Universe is luminous
99.5% of Universe is dark matter
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““Stellar Lenses”Stellar Lenses”Orion behind a Black HoleOrion behind a Black Hole
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Gravitational MicrolensesGravitational Microlenses
What are microlenses?– Stellar mass (or smaller) lenses– Images are unresovled (milliarcsecond separation) – Lens focuses light– Object appears brighter (several magnitudes!)
That’s absurd!– You’ll never see one in a million years!
Answer – just look at million stars every night!
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Microlensing SearchesMicrolensing Searches
Toward the Magellanic Clouds– MACHO (MAssive CompactHalo Objects collaboration)– EROS (Experience pour la Recherche d'Objets sombres)– DUO (Disk Unseen Objects)
Toward the Galactic Bulge– OGLE (Optical Gravitational Lensing Experiment)
Toward M31:– AGAPE (Andromeda Galaxy Amplified Pixel Experiment)– MEGA
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Ogling the Ogling the StarsStars
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AGAPE at M31AGAPE at M31
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Looking Through a LensLooking Through a Lens
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A Lens in MotionA Lens in Motion
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What You Really SeeWhat You Really See
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Looking for Lenses in HaystacksLooking for Lenses in Haystacks
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Frequency of EventsFrequency of Events
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How Big is the How Big is the Lens? Lens?
How Close did it How Close did it get?get?
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What are They?What are They?
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Follow-Up MonitoringFollow-Up Monitoring
PLANET (Probing Lensing Anomalies NETwork)Garching Spectroscopic Monitoring Group GMAN (Global Microlensing Alert Network)MPS (Microlensing Planet Search Project)MOA (Microlensing Observations in Astrophysics)
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Looking Through BifocalsLooking Through BifocalsBinary Stars as LensesBinary Stars as Lenses
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Binary Stars as LensesBinary Stars as Lenses
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Looking for PlanetsLooking for Planets
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The Planet SearchThe Planet Search
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Micolensing ResultsMicolensing Results They Exist! Future surveys will detect 1/day Fewer than expected toward LMC/SMC
– 50% of halo may be Machos (M = 0.5Msun) More than expected toward Galactic center
– Masses are few 0.1 Msun– May indicate presence of bar (i.e., Milky Way is a
barred spiral) About 10% are binary events Planets
– No definite detections, yet – Fewer that 1/3 of lenses have Jupiter-mass planets at
1-4 AU