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Probing Dark Energy with Cosmological Observations

Probing Dark Energy with Cosmological Observations. Fan, Zuhui (Dept. of Astronomy, Peking University) Representing many colleagues in the team: Xinmin Zhang (IHEP), Xuelei Chen(NAOC) ,Zonghong Zhu (BNU) and their fellow posdocs, and students. Outline Introduction

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Probing Dark Energy with Cosmological Observations

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  1. Probing Dark Energy with Cosmological Observations Fan, Zuhui (Dept. of Astronomy, Peking University) Representing many colleagues in the team: Xinmin Zhang (IHEP), Xuelei Chen(NAOC) ,Zonghong Zhu (BNU) and their fellow posdocs, and students

  2. Outline • Introduction • Current Status • Discussion • Future

  3. Introduction The development of cosmology is largely driven by observations

  4. The accelerating expansion of the universe  asks for something new Change the Matter content: Dark Energy Change the theory

  5. Cosmological studies on dark energy: Global expansion of the Universe cosmological distances, age, … The formation and evolution of the large-scale structures in the Universe

  6. Cosmological observables: SNeIa: luminosity distances (Global) LSS: structure formation BAO (angular diameter distances) CL: structure formation volume element (global)

  7. Weak Lensing: structure formation relative angular diameter distances (global) CMB: angular diameter distance (global) ISW (structure evolution) GRB, redshft distortion (growth factor)…… Most of the observables contain both sides of information

  8. Current observations: SNeIa: “Union” 307 (SNLS+ESSENCE+older ones) CMB: WMAP5, BOOMERanG, CBI, VSA,ACBAR…

  9. LSS: SDSS, 2dFGRS Weak Lensing: CITO, CFHTLS, …

  10. Current constraints on EoS of dark energy Komatsu et al. (2008) (WMAP distance priors )

  11. Xia et al. (2008): MCMC dark energy perturbations included (w cross -1) Cosmological constant remains to be an excellent fit Quintom models with w crossing -1:

  12. Discussions ** Dark energy perturbations: The existence of DE perturbations is inevitable for dynamical dark energy models By allowing w to cross -1, DE perturbations have to be analyzed properly: divergent terms if at w=-1

  13. Zhao et al. (2006), Xia et al. (2006) Dark energy perturbations are analyzed for two-fields Quintom models, and it is found that they are well behaved at the crossing point w=-1  develop a method and implement it into MCMC For (2): match (1) and (3) and the boundary and

  14. Effects of DE perturbations Notable influence on the ISW effect at small l Zhao et al. (2006)

  15. EoS of dark energy Xia et al. (2006)

  16. ** Distance priors from CMB

  17. easy to use; avoid the effect of DE perturbations Caveats: model dependent information loss (ISW) Li et al. (2008)

  18. Li et al. (2008) somewhat model dependent not sensitive to DE models

  19. information loss * without including DE perturbations: ISW plays significant roles * with DE perturbations: the DE information is almost fully contained in the distance priors

  20. ** Systematic effects For future high precision observations, systematic effects will become dominant source of errors. Thus detailed understanding are necessary. For example: Weak lensing * redshift distribution of source galaxies photo-z measurement * intrinsic alignments of source galaxies shear-ellipticity correlation * Nonlinear power spectrum * observational systematics * ……

  21. Sun et al. (2008): photo-z catastrophic errors

  22. * adding u-band observations * spectroscopic calibrations * finer bins in tomographic lensing analyses

  23. DETF • Future The future of “Dark” is bright Through investigations are needed

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