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Cosmic shear using Canada-France-Hawaii Telescope Legacy Survey (Wide)

This presentation discusses the cosmic shear measurements obtained from the Canada-France-Hawaii Telescope Legacy Survey, highlighting the pipeline reliability, cosmological parameter constraints, and the use of large-scale signals to reduce small-scale systematics. The results are consistent with previous measurements and provide valuable insights into dark energy and the evolution of the power spectrum.

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Cosmic shear using Canada-France-Hawaii Telescope Legacy Survey (Wide)

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  1. "From giant arcs to CMB lensing: 20 years of gravitational distortion" XXIIIrd IAP Colloquium July 2nd, 2007 Cosmic shear using Canada-France-Hawaii Telescope Legacy Survey (Wide) Liping Fu Institut d’Astrophysique de Paris

  2. Collaboration R. Maoli (U.Rome/IAP) F. Bernardeau (CEA/SPhT) M. Dantel-Fort (LERMA) F. Magnard (IAP) C. Marmo (IAP) M. Schultheis (Obs. Besançon) J.P. Uzan (IAP) C. Schimd (CEA/SPP and IAP) France: L. Fu (IAP) E. Semboloni (Bonn/IAP) • Tereno (Bonn/IAP) Y. Mellier (IAP) M. Kilbinger (IAP) J. Coupon (IAP) E. Bertin (IAP) H.J. McCracken (IAP) O. Ilbert (UBDA) K. Benabed (IAP) Canada: H. Hoekstra (U. Victoria) L. van Waerbeke (UBC, Vancouver) C. Heymans (UBC/IAP) J. Benjamin (UBC) S. Gwyn (U. Victoria) M. Hudson (U. Waterloo) L. Parker (U. Waterloo/ESO) B. Menard (CITA) U.L. Pen (CITA) O. Dore(CITA)

  3. Outline • Introduction to CFTHLS • Pipeline reliability • Cosmic shear on large scales • Cosmological parameter constraints

  4. I. Canada-France-Hawaii Telescope Legacy Survey

  5. Canada-France-Hawaii Telescope Legacy Survey: Canada-France collaboration - 500 nights between June 2003 and June 2008 - 4 CFHTLS-Wide ( 170 deg2 ), 4 CFHTLS-Deep ( 1 deg2 each ) W4 VVDS UKIDSS DXS • 3.6 m ground telescope • MegaCam: 36 CCDs, 1o × 1o • Pixel size: 0.186” • u g r i z bands W3 & D3 D2 HST Groth strip GEMINI-N visibility VLT visibility + HST-Cosmos D4 VLT visibility + Quasar field W2 W1 & D1 VLT visibility + XMM fields VVDS spectro. survey VLT visibility Terapix/Skywatcher : all data 03A-05A : 20000 Megacam images

  6. Sky coverage of CFHTLSWide (the 3rd release): 57 deg2 Number of Pairs W1 (19 deg2) W2 (8 deg2) W3 (30 deg2) • CFHTLS Wide: • 57 deg2 (35% completed) • W2 is new compared with 1st release • maglim= 24.5 i-band • Aeff= 35 deg2 (conservative masking); neff = 12 gal/arcm2 • 2.5 ×106 galaxies

  7. II. Pipeline reliability

  8. the multiplicative “calibration bias” the additive “residual shear offset” Unbiased shear measurement on Shear TEsting Program (STEP; see Kuijken’s talk) STEP1 STEP2 “0,…5” & “A,…F”: Realistic PSF models in simulations

  9. III. Cosmic shear on large scales using CFHTLS Wide (the 3rd release) Two publication (the 1st release): Semboloni et al., 2006 (Deep) Hoekstra et al., 2006 (Wide)

  10. Non-Gaussianity calibrated (Semboloni et al. 2006) Cosmic shear signal on large scales • Sky coverage: 57 deg2 • up to 460’ • up to:230’ • No B-mode • Error bars (Schneider et al. 2002):

  11. Large scales zoom in (26’~230’) • Reliable Shear analysis till 4 degrees • Large scales signal will reduce the effect of small scales systematics (non-linear evolution of power spectrum; intrinsic alignment)

  12. The consistency of W1, W2 and W3 • Scales up to: W1 200’ (19 deg2) W2 120’ (8 deg2) W3 230’ (30 deg2) • 2pt correlation functions Consistency !

  13. French Canadian Shear cross checking and systematics • Consistent shear signal • Common objects using two independent pipelines: • French: LF = L. Fu • Canadian: HH = H. Hoekstra • No systematics

  14. IV. Cosmological parameter constraints

  15. a single lens-plane + 21.5 < mag_i < 24.5 <z> = 0.926 Error bars: photo-z uncertainty + poisson error + sample variance (van Waerbeke et al, 2006) 0 12 3 4 z • Shear and cosmological parameters • Redshift distribution CFHTLS Deep Photo-z (500,000 galaxies, Ilbert et al. 2006) • Less complete • WL selection criteria • WL weighting scheme Bootstrap z

  16. flat model • likelihood of CS: , grid (other parameters are fixed) • likelihood of ; taken as a prior • Non-linear scheme: P&D (1996) and halo-fit (Smith et al., 2003) Non-linear scheme: halo-fit Marginalization:

  17. 1’~230’ 26’~230’ • Comparison of constraints from different scales Compare P&D and halo-fit model: • Full scales constraints: 2% difference • No small scales constraints: less than 1% difference • Systematics?

  18. CFHTLS-wide (1st) Aeff = 22 deg2 100 deg2 CFHTLS Wide + RCS + VIRMOS-DESCART + GaBoDS CFHTLS-wide (3rd) Aeff = 35 deg2 Comparison with previous constraints • Comparison with Benjamin et al., 2007

  19. WMAP3 CFHTLS Wide (3rd) • Comparison with WMAP3 (Spergel et al., 2006)

  20. Probing dark energy The constant equation of state: • Non-linear power spectrum (Peacock & Dodds, 1996) • Marginalizing over • Flat model (68% c.l.)

  21. Conclusion • Unbiased shear measurement calibrated on simulations and cross-checked with independent pipeline • Reliable Shear analysis up to large scales : 4 degrees • The use of large scales reduce the effect of small scales systematics (non-linear evolution of power spectrum; intrinsic alignment) • The cosmological parameter constraints (68% c.l.) • Constraints consistent with WMAP3 • The redshift degeneracy will be further minimized with the photometric redshifts measured from the new release (T4, Work in progress)

  22. Covariance matrix • Gaussian covariance matrix taking masking and survey geometry into account (Schneider et al. 2002) • Non-Gaussian calibration (Semboloni et al. 2006)

  23. Weighting scheme of weak lensing

  24. Weak lensing and Galaxy shape: Mellier 1999 PSF anisotropy correction Derived from star shape analysis. = s + i + noise + systematics…. δ ~ 2γ(weak lensing regime) Reliability of results: depends on PSF analysis Assume sources orientation is isotropic: Weak lensing regime :  ~ 2  = ‹Shear›+ noise

  25. Cosmic shear probes the dark matter power spectrum ( Blandford et al 1991, Miralda-Escudé 1991, Kaiser 1992,1998, Bernardeau et al 1997, Jain & Seljak 1997, Schneider et al 1998 ) 2D power spectrum • Two-point statistics • Convergence (projected mass) power spectrum Redshift distribution

  26. a Goal of CFHTLS Cosmic Shear Survey: observe P(k) and P(k,z) using weak lensing and compare its properties with cosmological models. Expansion and growth rate of structures as function of DM and DE content of the universe Weak lensing Supernovae

  27. ds2=c2dt2 - a2(t) [dw2 + fK2(w) d2] Deflection angle: Bartelmann & Schneider 2001; Erben 2002 Power spectrum, growth rate of structure Distances (Geometry) Weak gravitational lensing and cosmology:Light propagation in inhomogeneous universes Depend on dark matter and dark energy

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