1. Probing Dark Energy with Cosmological Observations Fan, Zuhui ( 范祖辉 ) Dept. of Astronomy Peking University

2. Outline  Introduction  Cosmological Probes  Current Status  Future

3. Introduction The development of cosmology is driven by observations

4. The universe is expanding ( ) – Big Bang Hubble

5. The expansion is accelerating ( ) (1998, 1999)

6. Standard cosmological scenario: Einstein ’ s equations govern the evolution of the universe R: scale factor of the universe

7. Normal matter: The accelerating universe calls for the existence of dark energy with negative pressure

8. Understanding the nature of dark energy Theoretical physics: dark energy models Cosmology: extract constraints on dark energy from different observations w=-1? w=constant? w(z) ?

9. Cosmological probes on dark energy  Global properties of the universe Geometry and expansion history of the universe  Dynamical evolution of the large-scale structure of the universe

10. Expansion of the universe: SNe Ia: standard candle  luminosity distance Clusters of galaxies: SZ+X-ray  angular diameter distance

11. Geometry of the universe: CMB: angular positions of the sound peaks sensitive to the total matter content

12. Dynamical evolution of the universe Large-scale structure of the universe galaxy redshift surveys power spectrum correlation function

13. detection of acoustic peak from the SDSS LRG sample Eisenstein et al. astro-ph/0501171

14. Dark energy dependence growth factor of density perturbations Cosmological distortion: AP test

15. The formation and evolution of clusters of galaxies abundance evolution: density growth volume element

16. gas fraction in clusters of galaxies assume the gas fraction f gas (z) invariant  constraints on cosmology (d A (z) – z relation)

17. Gravitational lensing strong lensing weak lensing dynamical evolution of density perturbations angular diameter distances to the source, to the lens, and from lens to the source

18. Current status SNe Ia ( Riess et al. 2004 astro-ph/0402512 ApJ, 607, 665 )

19. Dark energy constraints equation of state constant w

20. w(z)

21. Lyα+galaxy bias+SNe+CMB (Seljak et al. 2004, astro-ph/0407372, PRD, 71, 103515 (2005)) constant w

23. cluster gas fraction +CMB+SN (Rapetti et al. MNRAS, 360, 555 (2005))

24. equation of state

25. weak lensing (M. Jarvis et al. astro-ph/0502243) CTIO lensing survey: 75 deg 2, 19<R<23, 2*10 6 gal

26. dark energy constraint constant w

27. w(a) the second peak corresponds to w(a=0)~1 not physically relevant

29. As of today: w=-1 (cosmological constant) is consistent with all the observational data available to us Slightly favor w<-1

30.  Future SNe Ia SNAP Supernova/Acceleration Probe

31. Dark energy constraints

32. SNAP: weak lensing survey Deep survey: 15 deg 2, 250/arcmin 2 Wide survey: 300-1000 deg 2 100/arcmin 2 Panoramic survey: 10000 deg 2 40-50/acrmin 2

33. Equation of state

34. CMB: Planck standard ruler: sound horizon  baryon wiggles in matter power spectrum determination of other parameters Ω total, σ 8, Ω m, Ω b, … ISW Large-scale structure: LAMOST

35. LAMOST galaxy redshift survey (Sun, Su and Fan 2005) three redshift bins centered at 0.3, 0.4, and 0.5 distant observer approximation

36. With bins of higher redshifts, the constraints can be improved

37. Without distant-observer approximation z=0.2-0.4

38. a

39. Parameterization Priors systematic errors