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Slide 1
Gravitational Lensing Boot Camp Robert Nemiroff Michigan
Tech
Slide 2
Abstract What is gravitational lensing, what has it told us
about the universe, and what more can it tell us about the
universe? Lenses such as black holes, stars, galaxies, clusters of
galaxies, and the universe as a whole will be covered. Concepts
such as Einstein rings, photon spheres, image pair creation events,
and shear will be defined and briefly discussed. The intersection
of gravitational lensing with current research frontiers will be
reviewed including how microlensing is being used to search for
extra-solar planets, how radio telescopes are being used to probe
galaxy-center black holes, and how weak lensing is being used to
probe galaxy evolution in the early universe. Possible lensing
signals in continuing and upcoming missions such as Planck, DES,
LSST, Euclid, and WFIRST will be reviewed. Relevant parts of the
lecturer's own research will also be briefly mentioned.
Slide 3
Lensing: Suggested readings Wikipedia
http://en.wikipedia.org/wiki/Gravitational_lensing Short
http://astro.berkeley.edu/~jcohn/lens.html Medium Visual
distortions near a neutron star and black hole, R. J. Nemiroff,
1993 http://adsabs.harvard.edu/abs/1993AmJPh..61..619N Movies:
http://apod.nasa.gov/htmltest/rjn_bht.html Long Microlensing
Surveys for Exoplanets, Gaudi, S. 2012
http://adsabs.harvard.edu/abs/2012ARA%26A..50..411G
Slide 4
Know Your Lecturer (highlights) Prediction & analysis of
basic microlensing phenomena Nemiroff, 1987, Ph D., U. Penn. AGN
broad emission line amplification from microlensing Nemiroff, 1988,
Astrophys. J, 335, 593 Visual distortions near a neutron star and
black hole Nemiroff, 1993, Am. J. Phys., 61, 619 Finite sources
& the information content of microlensing Nemiroff &
Wickramasinghe 1994, Astrophys. J., 424, L21 Gravitational Lensing
Characteristics of the Transparent Sun Patla & Nemiroff 2008,
Astrophys. J. 285, 1297 Also papers on cluster arcs, GRB lensing
searches,etc.
Lensing: History 1801: Soldner with Newtonian gravity 1911
& 1915: Einstein with relativistic theories 1912: Failed
attempt to find solar lensing 1919: Eddington et al. detect solar
lensing 1979: Walsh et al. detect galaxy lensing 1986: Lynds &
Petrosian recognize cluster lensing 1993: MACHO, EROS, OGLE find
stellar lensing GR might be wrong but GL is certainly correct!
Slide 7
Lensing: Outline Concepts Einstein rings, photon spheres,
magnification, shear, image pair creation events Lenses Universe,
clusters of galaxies, galaxies, stars, black holes Frontiers
Extra-solar planets, galaxy center black holes, cosmic
tomography
Slide 8
Lensing: Outline Concepts Einstein rings, photon spheres,
magnification, shear, image pair creation events Lenses Universe,
clusters of galaxies, galaxies, stars, black holes Frontiers
Extra-solar planets, galaxy center black holes, cosmic
tomography
Slide 9
Concepts Einstein Ring Observed ring when point source is
directly behind a point lens Photon sphere Distance from black hole
where photons orbit in circles (unstable) Magnification Images
become brighter or dimmer Shear Tangential stretching Image pair
creation event And other light curve features
Slide 10
Credit: NASA, Wikipedia: Gravitational Lens Concept: Einstein
Ring
Slide 11
Nemiroff, R. J. 1993, AmJPhys Orbiting near a black hole
Concept: Photon SphereConcept: Einstein Ring
Slide 12
Nemiroff, R. J. 1993, AmJPhys
Slide 13
Wambsganss, 1998, Living Reviews Single star light curves
Concept: Magnification
Slide 14
Nemiroff, Ph D. thesis, 1987 Double star light curves Concept:
Image pair creation events
Slide 15
Concept: Image pair creation event Concept: Shear Time Delay
Surface ERU = Einstein Ring Unit Nemiroff, R. 1988, Astrophys.
Space Sci
Slide 16
Terminology: Strong vs. Weak Strong lensing Multiple images,
large deflections Microlensing, galaxy lensing, femtolensing, etc.
Galaxy halo probe, exoplanets, dark matter Weak lensing Single
displaced images, small deflections Galaxies, distortions and tests
of cosmology
Slide 17
Lensing: Outline Concepts Einstein rings, photon spheres,
magnification, shear, image pair creation events Lenses Universe,
clusters of galaxies, galaxies, stars, black holes Frontiers
Extra-solar planets, galaxy center black holes, cosmic
tomography
Slide 18
Lensing: Outline Concepts Einstein rings, photon spheres,
magnification, shear, image pair creation events Lenses Universe,
clusters of galaxies, galaxies, stars, black holes Frontiers
Extra-solar planets, galaxy center black holes, cosmic
tomography
Slide 19
Lens: Universe Standard Rulers Angular size changes can be
strange Galaxies radius Baryon Acoustic Oscillations Standard
Candles Dimming with distance depends on cosmology Perfect candles
still have lensing dispersion Universe is not WYSIWYG! WYSIWIG=What
You See Is What You Get (A computer term)
Slide 20
Strani & Strabinski, 2000, Mod. Phys. D., 9, 373-443 Lens:
Universe
Slide 21
Lens: Cluster of galaxies Dark matter fraction constraints
Positions of arcs Smoothness arcs Not predicted because central
density thought smaller Seen before it was noticed!
Slide 22
Lens: Cluster of Galaxies: Abell 2218 Credit: Andrew Fruchter
(STScI) et al., WFPC2, HST, NASA Digitally reprocessed: Al
Kelly
Slide 23
Lens: Galaxy Source: Quasars Mass distribution of galaxies Time
delay between images and Hubbles constant Source: Background
galaxies 2D lens mass 3D universe mass distribution
Slide 24
The Einstein Cross Gravitational Lens Image Credit &
Copyright: J. Rhoads (Arizona State U.) et al., WIYN, AURA, NOAO,
NSF Lens: Galaxy
Slide 25
Image Credit: ESA/Hubble & NASA Lens: Galaxy: LRG
3-757
Slide 26
Lens: Star Source star light curves only Not resolved
angularly
Slide 27
Lens: Black Hole Strong lensing Very high deflection angles
Many images Complete image sets No confirmed BH lenses
Slide 28
Nemiroff, R. J. 1993, AmJPhys Orbiting at the photon sphere
Lens: Black Hole
Slide 29
Lensing: Outline Concepts Einstein rings, photon spheres,
magnification, shear, image pair creation events Lenses Universe,
clusters of galaxies, galaxies, stars, black holes Frontiers
Extra-solar planets, galaxy center black holes, cosmic
tomography
Slide 30
Lensing: Outline Concepts Einstein rings, photon spheres,
magnification, shear, image pair creation events Lenses Universe,
clusters of galaxies, galaxies, stars, black holes Frontiers
Extra-solar planets, galaxy center black holes, cosmic
tomography
Slide 31
Frontier: Extra-solar planets (Microlensing) Gaudi, S. 2012,
Ann. Rev. Astron. Astrophy.
Slide 32
Frontier: Galaxy Center Black Holes Very Long Baseline
Interferometry Radio Interferometry Event Horizon Telescope
(preliminary obs. ongoing) Photon sphere shadow on bright material
behind Sgr A* and M87s center Localizing Sgr A* with VLBI,
Borderick, Loeb, & Reid, ApJ (2011) Very Large Telescope (ESO)
Infrared Interferometry GRAVITY 10 microarcsec astrometry (2014)
Star deviations from Sgr A* lensing Observing Gravitational Lensing
Effects by Sgr A* with GRAVITY, Bozza & Mancini, ApJ
(2012)
Slide 33
Frontier: Cosmic Tomography (Weak Lensing)
Slide 34
Determine mass power spectrum Clusters of galaxies As matter
clumps during universe evolution Ground Pan-STARRS (ongoing) Dark
Energy Survey (ongoing) LSST (2014) Space Planck (2013) WFIRST
(2023)
Slide 35
Lensing: My research Predictions Probability & Detection
Volumes Microlensing of AGN Microlensing of stars Dark matter
searches for millilensing in GRBs Strong effects near a black hole
Neutron star
Slide 36
Nemiroff et al. 2001, Phys. Rev. Lett Searching the universe
for million solar mass lenses
Slide 37
Surprise: Philosophy slide! There are only three numbers in
science Zero (0) It is too small to measure. Example: electron
radius One (1) We measured it and normalized it. Example: Sun-Earth
distance Infinity ( ) It is too large to measure. Example: complete
universe radius