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Presentation on theme: " 1/19 PASCAL Challenge."— Presentation transcript:

1 1/19 PASCAL Challenge

2 2/19

3 3/19 Contents of our Universe 70% Dark Energy 25% Dark Matter 5% Baryonic Matter

4 4/19 Gravitational Lensing Light from a distant galaxy is bent around a mass

5 5/19 Gravitational Lensing Galaxies seen through dark matter distribution analogous to Streetlamps seen through your bathroom window

6 6/19

7 7/19 Cosmic Lensing Real data: g i ~0.03 g i ~0.2

8 8/19 Atmosphere and Telescope Convolution with kernel Real data: Kernel size ~ Galaxy size

9 9/19 Pixelisation Sum light in each square Real data: Pixel size ~ Kernel size /2

10 10/19 Noise Mostly Poisson. Some Gaussian and bad pixels. Uncertainty on total light ~ 5 per cent

11 11/19

12 12/19 Typical star Used for finding Convolution kernel Typical galaxy used for cosmic shear analysis

13 13/19

14 14/19 GREAT08 Data One galaxy per image Kernel is given One shear per set Noise is Poisson galaxies galaxies galaxies galaxies All divided into sets containing galaxies each

15 15/19 GREAT08 Data

16 16/19 GREAT08 Results You submit g 1, g 2 for each set of images

17 17/19 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

18 18/19 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

19 19/19 GREAT08 Summary 30 million images 1 galaxy per image De-noise, de-convolve, average shear g i ~ 0.03 to accuracy Q~1000 Win!

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