1. www.great08challenge.infowww.cosmocoffee.info 1/19 PASCAL Challenge

2. www.great08challenge.infowww.cosmocoffee.info 2/19

3. www.great08challenge.infowww.cosmocoffee.info 3/19 Contents of our Universe 70% Dark Energy 25% Dark Matter 5% Baryonic Matter

4. www.great08challenge.infowww.cosmocoffee.info 4/19 Gravitational Lensing Light from a distant galaxy is bent around a mass

5. www.great08challenge.infowww.cosmocoffee.info 5/19 Gravitational Lensing Galaxies seen through dark matter distribution analogous to Streetlamps seen through your bathroom window

6. www.great08challenge.infowww.cosmocoffee.info 6/19

7. www.great08challenge.infowww.cosmocoffee.info 7/19 Cosmic Lensing Real data: g i ~0.03 g i ~0.2

8. www.great08challenge.infowww.cosmocoffee.info 8/19 Atmosphere and Telescope Convolution with kernel Real data: Kernel size ~ Galaxy size

9. www.great08challenge.infowww.cosmocoffee.info 9/19 Pixelisation Sum light in each square Real data: Pixel size ~ Kernel size /2

10. www.great08challenge.infowww.cosmocoffee.info 10/19 Noise Mostly Poisson. Some Gaussian and bad pixels. Uncertainty on total light ~ 5 per cent

11. www.great08challenge.infowww.cosmocoffee.info 11/19

12. www.great08challenge.infowww.cosmocoffee.info 12/19 Typical star Used for finding Convolution kernel Typical galaxy used for cosmic shear analysis

13. www.great08challenge.infowww.cosmocoffee.info 13/19

14. www.great08challenge.infowww.cosmocoffee.info 14/19 GREAT08 Data One galaxy per image Kernel is given One shear per set Noise is Poisson 150 000 galaxies 27 000 000 galaxies 3 000 000 galaxies 150 000 galaxies All divided into sets containing 10 000 galaxies each

15. www.great08challenge.infowww.cosmocoffee.info 15/19 GREAT08 Data

16. www.great08challenge.infowww.cosmocoffee.info 16/19 GREAT08 Results You submit g 1, g 2 for each set of images

17. www.great08challenge.infowww.cosmocoffee.info 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. www.great08challenge.infowww.cosmocoffee.info 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 www.great08challenge.info

19. www.cosmocoffee.info 19/19 GREAT08 Summary 30 million images 1 galaxy per image De-noise, de-convolve, average shear g i ~ 0.03 to accuracy 0.0003 Q~1000 Win!