March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia1 GRAVITATIONAL LENSING GRAVITATIONAL LENSING History, Discovery and Future Measuring Mass of Dark Matter Vahe’ Petrosian Vahe’ Petrosian Stanford University Stanford University Yerevan, April 23, 2009

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia2 HOW? HOW? 1. Visible Ordinary Matter: Stars and Galaxies Measure light, Infer Mass Measure light, Infer Mass 2. Invisible Ordinary Matter: Hot Gas, Small Stuff X-ray Emission in Clusters of Galaxies X-ray Emission in Clusters of Galaxies 3. Dark Matter: a. How Much? b. What is it made of? b. What is it made of? WIMPS or MACHOS? WIMPS or MACHOS? Measuring Mass In the Universe Measuring Mass In the Universe

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia3 HOW? HOW? 1. Visible Ordinary Matter: Stars and Galaxies Measure light, Infer Mass Measure light, Infer Mass 2. Invisible Ordinary Matter: Hot Gas, Small Stuff X-ray Emission in Clusters of Galaxies X-ray Emission in Clusters of Galaxies 3. Dark Matter: a. b. What is it made of? WIMPS or MACHOS? WIMPS or MACHOS? Measuring Mass In the Universe Measuring Mass In the Universe

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia4 HOW? HOW? 1. Visible Ordinary Matter: Stars and Galaxies Measure light, Infer Mass Measure light, Infer Mass 2. Invisible Ordinary Matter: Hot Gas, Small Stuff X-ray Emission in Clusters of Galaxies X-ray Emission in Clusters of Galaxies 3. Dark Matter: a. b. What is it made of? WIMPS or MACHOS? WIMPS or MACHOS? Measuring Mass In the Universe Measuring Mass In the Universe

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia5 Measuring Dark Matter Newton and Einstein Measuring Dark Matter Newton and Einstein Gravitational Influence Gravitational Influence 1. On Other Matter: Motions and Orbits 1. On Other Matter: Motions and Orbits Planets, Stars, Galaxies Planets, Stars, Galaxies 2. On Light: Gravitational Lensing 2. On Light: Gravitational Lensing Arcs in Clusters of Galaxies Arcs in Clusters of Galaxies

A Brief History of Gravitational Lensing Basis: Deflection of Light By Matter NEWTON (Optics 1704) “Do not bodies act upon light… and bend it?” SOLDNER (1801) Deflection of Light Einstein (1911) based on Special Relativity March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia6

A Brief History of Gravitational Lensing EINSTEIN (1915) General Relativity March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia7

A Brief History of Gravitational Lensing EDDINGTON (1919) EDDINGTON (1919)Confirmation Double Image March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia9 EINSTEIN’s RING EINSTEIN’s RING If Source, Lens and Observer aligned If Source, Lens and Observer aligned CHOWLSON (1924) Ring Image EINSTEIN (1936); suggested by Mendel Ring Ang. Radius

Star-Star Lensing: Einstein Radius Image Magnification Star-Star Lensing: Einstein Radius Image Magnification March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia10 Magnification Probability of Alignment Einstein : Hopeless. Can scarcely approach alignment and resolve the ring.

Galaxy Lensing: ZWICKY (1937) Galaxy Lensing: ZWICKY (1937) March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia11 1. Galaxy-Galaxy 2. Galaxy-Cluster “….difference in redshifts……will immediately betray the presence of gravitational lens effect”

Revival of the Field Revival of the Field RESDAL, KILMER, LIEBS (1963) Details, Measuring Hubble Constant, Mass BARNOTHY’s (~1967) Quasars as Magnified Seifert Galaxies Several PhD Thesis ( Gunn, Petrosian, Kontowski ) Dealing with Statistical Lensing Nowadays called WEAK LENSING March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia12

OBSERVATIONS OBSERVATIONS 1. DOUBLE QUASARS Walsh, Carswell and Weymann (1979) 2. ARCS IN CLUSTERS OF GALAXIES Lynds and Petrosian (1986) Lynds and Petrosian (1986) Originally Discovered Circa 1976 March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia13

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia14 Discovery of Gravitational Lens Roger Lynds and Vahe Petrosian: circa 1976 Discovery of Gravitational Lens Roger Lynds and Vahe Petrosian: circa 1976

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia15 Hubble Space Telescope View Hubble Space Telescope View

A complete Einstein ring. Examples of Strong Lensing Galaxy at z =1.7 multiply imaged by a cluster at z = 0.4. Multiply imaged quasar (with time delays).

Some Significant Applications Some Significant Applications 1. Arcs and Strong Lensing Mass & Distribution of Dark Matter 2. Weak Lensing from Image Distortions Large Scale Structure of Universe 3. Microlensing: Detecting ‘Dark Stars’ & Planets March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia17

1. ARCS & STRONG LENSING March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia18 Mass of Dark Matter in Clusters Mass of Dark Matter in Clusters (Bergmann \& Petrosian 1990) (Bergmann \& Petrosian 1990) Distribution of Dark Matter Distribution of Dark Matter Different than Hot Gas : Different than Hot Gas : Narrower and More Peaked Narrower and More Peaked (Saraniti & Petrosian 1997) (Saraniti & Petrosian 1997)

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia19

1. ARCS & STRONG LENSING March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia20 Mass of Dark Matter in Clusters Mass of Dark Matter in Clusters (Bergmann \& Petrosian 1990) (Bergmann \& Petrosian 1990) Distribution of Dark Matter Distribution of Dark Matter Different than Hot Gas : Different than Hot Gas : Narrower and More Peaked Narrower and More Peaked (Saraniti & Petrosian 1997) (Saraniti & Petrosian 1997)

21 Hubble Image of Cluster and Arcs

Reconstruction of Dark Matter Distribution (Tyson et al.) March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia22

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia23 Dark Matter in a Merging Cluster From: Bradac et al From: Bradac et al. 2006

Simulation by S. Colombi (IAP, France). Weak Lensing of Distant Galaxies Lensing is sensitive to all matter

Large Area Synoptic Telescope Large Area Synoptic Telescope March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia25 Primary mirror diameter Field of view Keck 0.2 degrees 10 m 3.5 degrees LSST

Simulation of Lensing: Moving Clusters ~Few Billion Years March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia26 Clumpier Dark Matter Distribution Smoother Dark Matter Distribution From T. A. Tyson

SDSS LSST SDSS LSST March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia27

3. MICROLENSING: Finding Dark “Stars” or MACHOS 3. MICROLENSING: Finding Dark “Stars” or MACHOS March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia28 The MACHO Project

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia29 Microlensing: Finding Dark “Stars” or MACHOS Microlensing: Finding Dark “Stars” or MACHOS

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia30 Microlensing: Finding Dark “Stars” or MACHOS Microlensing: Finding Dark “Stars” or MACHOS

Som e Observed Light Curves From The Macho Project Som e Observed Light Curves From The Macho Project March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia31

DETECTING PLANETS with masses of a FEW EARTH MASS From Waumbgassen DETECTING PLANETS with masses of a FEW EARTH MASS From Waumbgassen March 7, 2016March 7, 2016March 7, 2016 Yerevan, Armenia32

SUMMARY SUMMARY 1. Strong and Weak Gravitational Lensing have proven to be one of the most important pillars of Modern Observational Cosmology and for measuring Dark Matter and Dark Energy 2. Microlensing has shown that Most of the Dark Matter is made of WIMPS Most of the Dark Matter is made of WIMPS And has the potential of discovering Rocky Planets And has the potential of discovering Rocky Planets March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia33

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia34 Measuring Mass of the Sun Measuring Mass of the Sun

March 7, 2016March 7, 2016March 7, 2016Yerevan, Armenia35 Measuring Mass of The Milky Way Using Satellite Galaxies