1. Measuring dark energy from galaxy surveys Carlton Baugh Durham University London 21 st March 2012

2. Galaxies to cosmological parameters

3. Connecting dark matter to linear theory Linear perturbation theoryEvolved matter distribution: MXXL Angulo et al. 2012

4. Connecting galaxies to mass H-  H-band Orsi et al. 2010

5. A hybrid tool to study dark energy N-body simulation Galaxy formation simulation

6. Bias and nonlinear effects Angulo et al. 2008

7. Scale dependent biases Linear theory Dark matter Angulo et al. 2008

8. Scale dependent RSD Jennings et al. 2011 Linear theory

9. Scale dependent RSD Jennings et al. 2011

10. The need for improved RSD models Jennings et al. 2011 Using linear theory leads to systematic errors similar to difference in signal

11. Measuring DE using galaxy pairs Peculiar motions distort apparent distribution of pair angles: Jennings et al. 2012 Marinoni & Buzzi 2010

12. A probe of dark energy Peculiar velocities give distortion in pair angle distribution Probe of Hubble expansion Distortion sensitive to nature of dark energy Distinguish models with same BAO and halo mass function Requires simulations Jennings et al. 2012

13. Why build a mock catalogue? A synthetic galaxy can catalogue be used to: Test estimators: e.g. Galaxy clustering, photo-z, group-finders Devise new statistics: e.g. pair distortions Uncover systematic effects (we already know the right answer) Estimate errors Generate predictions for different dark energy cosmologies

14. What is a mock catalogue? N-body simulation Combine with galaxy formation model Millennium, Horizon, MICE, MXXL e.g. GALFORM; GALICS, LGALAXIES; MORGANA Springel et al. 2005, Teyssier et al. 2009; Fosalba et al 2008; Angulo et al. 2012 Cole et al. ;Hatton etal; de Lucia et al; Monaco + A priori calculation of baryon physics STEP 1 STEP 2

15. Build galaxy catalogue on observer’s past lightcone. Constructing observer’s past lightcone redshift STEP 3 e.g. Blaizot et al 2005; Fosalba et al. Kitzbichler & White; Merson et al.

16. Apply survey “window function” Apply angular footprint Apply scanning mask Incorporate sampling Redshift completeness (synergy with OU-SIM) Steps 1, 2, 3 generic Step 4 is survey specific

17. Synthetic images

18. Merson et al. 2012

21. Summary Hybrid tool: N-body and galaxy formation sims Linear theory not accurate enough for Euclid on large-scales Scale dependent: nonlinearities, bias, RSD Mock catalogues will help refine estimators Devise new tests