weak gravitational lensing slides
DESCRIPTION
Presentation slides for the Weak Lensing presentation Patrick Kantorski and Cory Gerrity gave for UC Berkeley's Astro C161 Course, Spring 2015.TRANSCRIPT

Weak Gravitational Lensing
Image Source: NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)
By Patrick Kantorski & Cory Gerrity

Introduction What is Weak Gravitational Lensing?
Image Source: Astrophysicist Dr. Katherine J Mack
Why is Weak Gravitational Lensing important? What are some of the fundamental limitations and assumptions?

Methodology
Previous Presentation: ThinLens Approximation
Transformation: Lensed Unlensed via Jacobian Matrix Formalism
Symmetry of Partial Derivatives > Decomposition [Diagonal Convergence Term + TraceFree Shear Term]

What is Convergence?
What is Shear?
Convergence by Jackson Pollock
The second term in action.
Methodology
Image Source: Schneider, P. 2005
Shear and Convergence Transformations

Scale of Weak Lensing Survey
Small Scale Limits  Intrinsic ellipticities
 Add Shot Noise  Limited by Depth of Survey
Large Scale Limits:  Large Sky Coverage
 Limited by Variance Image Source: Wikipedia.org

Observational Considerations Applying the Shear Method
Source to Image Ellipticity Minimum Lens Strength Magnication Eects
Observational Instruments Size of Telescope Size of CCD Camera
Working with Instruments Exposure Time Seeing Conditions
Apparent Size of Galaxies vs. Faintness
Image Source: Schneider, P. 2005

Observational Considerations Mean Number Density of Galaxy Images vs. Seeing
Source: Schneider, P. 2005

Observational Challenges Data Reduction
Individual Frames
Coaddition
Image Analysis The PointSpread Function
Shape Measurements Numerical Algorithms
Shear Observations from Space Image Source: Wikipedia.org
PointSpread Function (PSF)

Mass Reconstruction
Kaiser ~ Squires Inversion Surface Mass Density from Shear
Convolution Product: Fourier Transform Solve for Mass Density > Transform Back
Discrete Process Requires Smoothing > Kernel Prevents Summation
[Kaiser & Squires (1993)]

Dark Matter Mass Reconstruction (k contours) for COSMOS Advanced Camera for Surveys (ACS) 2 square degree eld. The Mass Density along LOS is Proportional to k.
Dark Matter Map from Hubble Space Telescope Survey and the Cosmic Evolution Survey

Dark Matter Map from Hubble Space Telescope Survey and the Cosmic Evolution Survey

Dark Matter Map from Hubble Space Telescope Survey and the Cosmic Evolution Survey

Creation of cosmic structure in the complex galaxy cluster merger Abell 2744
Image Source: Merten, J. 2011

On the Horizon Euclid (2020), ESA
15,000 Square Degree Weak Lensing Survey in 3 NIR Filters 24.5 Magnitude Resolution, 550900 nm
Square Kilometer Array (2022), Australia/South Africa Large RA Instrument will allow 50x higher sensitivity than any other
Large Synoptic Survey Telescope (2022), El Pen, Chile Large Field/High Z Capability Mass Map of Universe to Half Current Age

On the Horizon
The LSST is a new kind of telescope. With a lightgathering power among
the largest in the world, it can detect
faint objects with short exposures. Its
uniquely wide eld of view allows it
to observe large areas of the sky at
once; compact and nimble, it can
move quickly between images.
Taking more than 800 panoramic
images each night, it can cover the
sky twice each week.  LSST.org
Large Synoptic Survey Telescope
Image Source: news.slac.stanford.edu

Conclusion Why pursue research applying Gravitational Lensing?
Gravitational Lensing is used to produce largeeld survey maps of the Universe!
By mapping where regions of Dark Matter, we can understand more about its properties and properties of galaxy clusters!
Weaklensing is a fairly new method due to recent technological advancements! There will also be many improvements to its
application the coming years! (Euclid, LSST, etc)
Gravitational Lensing Video