Gravitational lensing how to see the dark
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Gravitational Lensing: How to See the Dark. J. E. Bjorkman University of Toledo Department of Physics & Astronomy. The Dark Between the Light. Dark 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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Gravitational Lensing: How to See the Dark

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Gravitational lensing how to see the dark

Gravitational Lensing: How to See the Dark

J. E. BjorkmanUniversity of Toledo

Department of Physics & Astronomy

The dark between the light

The Dark Between the Light

Dark matter

Dark Matter

  • How do we know its there?

  • Answer: It affects the motion of everything we can see.

    • Cluster Simulation

    • Rotation Velocities

Galactic rotation curves

Galactic Rotation Curves

Missing mass in our galaxy

Missing Mass in our Galaxy

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.

Where is the dark

Where is the Dark?

Gravity bends light einstien

Gravity Bends Light (Einstien)

Gravitational lenses

Gravitational Lenses

Gravitational lensing how to see the dark

Einstein tells Eddington gravity bends starlight.

Eclipse astrometry

Eclipse Astrometry

  • How do we know the stars moved?

Relativity verified

Relativity Verified

Discovery of a gravitational lens

Discovery of a Gravitational Lens

Galaxies as lenses

Galaxies as Lenses

A lensing simulation

A Lensing Simulation

A lens gallery

A Lens Gallery

Galaxy clusters as lenses

Galaxy Clusters as Lenses

Measuring the dark

Measuring the Dark

  • 0.5% of Universe is luminous

  • 99.5% of Universe is dark matter

Stellar lenses orion behind a black hole

“Stellar Lenses”Orion behind a Black Hole

Gravitational microlenses

Gravitational 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!

Microlensing searches

Microlensing 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

Ogling the stars

Ogling the Stars

Agape at m31

AGAPE at M31

Looking through a lens

Looking Through a Lens

A lens in motion

A Lens in Motion

What you really see

What You Really See

Looking for lenses in haystacks

Looking for Lenses in Haystacks

Frequency of events

Frequency of Events

How big is the lens how close did it get

How Big is the Lens? How Close did it get?

What are they

What are They?

Follow up monitoring

Follow-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)

Looking through bifocals binary stars as lenses

Looking Through BifocalsBinary Stars as Lenses

Binary stars as lenses

Binary Stars as Lenses

Looking for planets

Looking for Planets

The planet search

The Planet Search

Micolensing results

Micolensing 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

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