Download Powerpoint slides - GREAT08 Challenge

PASCAL Challenge
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• The Problem
•The Challenge
•The Simulations
•The Story So Far
•The Future ...
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Contents of our Universe
70% Dark Energy
5% Baryonic
Matter
25% Dark Matter
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Gravitational Lensing
Light from a distant galaxy is bent around a mass
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Gravitational Lensing
Galaxies seen through dark matter distribution
analogous to
Streetlamps seen through your bathroom window
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Cosmic Lensing
gi~0.2
Real data:
gi~0.03
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Atmosphere and Telescope
Convolution with kernel
Real data: Kernel size ~ Galaxy size
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Pixelisation
Sum light in each square
Real data: Pixel size ~ Kernel size /2
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Noise
Mostly Poisson. Some Gaussian and bad pixels.
Uncertainty on total light ~ 5 per cent
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Typical galaxy
used for cosmic
shear analysis
Typical star
Used for finding
Convolution kernel
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GREAT08 Data
150 000 galaxies
3 000 000 galaxies
One galaxy per image
Kernel is given
One shear per set
Noise is Poisson
150 000 galaxies
27 000 000 galaxies
All divided into sets containing 10 000 galaxies each
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GREAT08 Data
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GREAT08 Results
You submit g1, g2 for each set of images
Goal:
Q = 1000
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GREAT08 Results
Low Noise
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GREAT09 and Beyond
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Kernel is not given (just kernel images)
Galaxies with more complicated shapes
Kernel is more realistic
Many objects in each image
Correlated noise
Poisson + Gaussian noise + bad pixels
Shear is different for each galaxy
Kernel is not the same for every galaxy
Cosmic rays, satellite tracks, saturated stars
Multiple exposures
Pixels not exactly square or on a grid
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GREAT08 Timeline
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Feb 2008 GREAT08 Handbook public
Jun 2008 Internal release of simulations
Aug 2008 First simulations public
27 Oct 2008 Launch of public challenge
– Leaderboard starts containing internal results
• 5 Jan 2009 – mid-term workshop at UCL
• 30 Apr 2009 Competition deadline
• ~June 2008 Workshop; Release final report
– Input shears public
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GREAT08 Summary
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30 million images
1 galaxy per image
De-noise, de-convolve, average → shear
gi ~ 0.03 to accuracy 0.0003 → Q~1000 → Win!
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