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PASCAL Challenge

PASCAL Challenge. The Problem The Challenge The Simulations The Story So Far The Future. Contents of our Universe. 70% Dark Energy. 5% Baryonic Matter. 25% Dark Matter. Gravitational Lensing. Light from a distant galaxy is bent around a mass. Gravitational Lensing.

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PASCAL Challenge

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  1. PASCAL Challenge

  2. The Problem • The Challenge • The Simulations • The Story So Far • The Future ...

  3. Contents of our Universe 70% Dark Energy 5% Baryonic Matter 25% Dark Matter

  4. Gravitational Lensing Light from a distant galaxy is bent around a mass

  5. Gravitational Lensing Galaxies seen through dark matter distribution analogous to Streetlamps seen through your bathroom window

  6. Cosmic Lensing gi~0.2 Real data: gi~0.03

  7. Atmosphere and Telescope Convolution with kernel Real data: Kernel size ~ Galaxy size

  8. Pixelisation Sum light in each square Real data: Pixel size ~ Kernel size /2

  9. Noise Mostly Poisson. Some Gaussian and bad pixels. Uncertainty on total light ~ 5 per cent

  10. Typical galaxy used for cosmic shear analysis Typical star Used for finding Convolution kernel

  11. GREAT08 Data 150 000 galaxies 3 000 000 galaxies 150 000 galaxies One galaxy per image Kernel is given One shear per set Noise is Poisson 27 000 000 galaxies All divided into sets containing 10 000 galaxies each

  12. GREAT08 Data

  13. GREAT08 Results You submit g1, g2 for each set of images Goal: Q = 1000

  14. GREAT08 ResultsLow Noise

  15. GREAT09 and Beyond • 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

  16. GREAT08 Timeline • 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 www.great08challenge.info

  17. GREAT08 Summary • 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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