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Cosmological Weak Lensing With SKA in the Planck era. Y. Mellier. SKA, IAP, October 27 , 2006. Cosmic shear : propagation of light through the cosmic web. ~ Gpc. Cosmological distortion field projected on the sky.

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Cosmological Weak Lensing With SKA in the Planck era


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    1. Cosmological Weak Lensing With SKA in the Planck era Y. Mellier SKA, IAP, October 27 , 2006

    2. Cosmic shear : propagation of light through the cosmic web ~ Gpc

    3. Cosmological distortion field projected on the sky

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

    5. Properties of Dark energy in the Planck era: measuring very small effects, DE dominated era at small z (good for WL)

    6. Cosmic shear surveys and dark cosmological models : exploring the power spectrum z=2 z=1

    7. Shapes and Shear: practicing WL Mellier 1999 κ PSF anisotropy correction Derived from star shape analysis. Image quality of primary importance for weak lensing = 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

    8. I. The shape and amplitude of the signal is in very good agreement with gravitational instability paradigm in a CDM-dominated universe. (Blandford el al 1991, Miralda-Escudé 1991, Kaiser 1992, 1998, Bernardeau et al 1997, Jain & Seljak 1997, Schneider et al 1998) Top-Hat Shear variance (observed) Top-Hat Shear variance (predicted) Map variance Non-Linear Non_linear Linear Linear Refregier et al 2002 Bartelmann & Schneider 2001 : theoretical predictions from the gravitational instability scenario See: Bacon et al 2000* , 2001 ; Kaiser et al. 2000* ; Maoli et al. 2000* ; Rhodes et al 2001* ; Refregier et al 2002 ; van Waerbeke et al. 2000* ; van Waerbeke et al. 2001, 2005 ; Wittman et al. 2000* ; Hammerle et al. 2001* ; Hoekstra et al. 2002 * ; Brown et al. 2003 ; Hamana et al. 2003 * ; Jarvis et al. 2003 ; Casertano et al 2003* ; Rhodes et al 2004 ; Massey et al. 2004 ; Heymans et al 2004* ; Semboloni et al 2006 ; Hoekstra et al 2005, Hetterscheidt et al 2006, Schrabback et al 2006, Fu et al 2006

    9. Cosmic shear and dark energy Cosmic shear is a unique way to explore the dark matter power spectrum P(k,z) directly • Galaxy ellipticity • Galaxy redshift

    10. Cosmic shear and dark energy Cosmic shear is a unique way to explore the dark matter power spectrum P(k,z) directly • Galaxy ellipticity • Galaxy redshift • Power spectrum • Bispectrum • Decoupling geometry/P(k) • Tomography • Control systematics

    11. Cosmic shear and dark energy Cosmic shear is a unique way to explore the dark matter power spectrum P(k,z) directly • Galaxy ellipticity • Galaxy redshift • Power spectrum • Bispectrum • Decoupling geometry/P(k) • Tomography • Control systematics Dark energy properties

    12. Cosmic shear and dark energy Cosmic shear is a unique way to explore the dark matter power spectrum P(k,z) directly • Need high image quality • Accurate PSF correction • Accurate galaxy redshift • Large FOV for linear power spectrum • Large FOV for cosmic variance • Galaxy ellipticity • Galaxy redshift • Power spectrum • Bispectrum • Decoupling geometry/P(k) • Tomography • Control systematics Dark energy properties

    13. Errors and systematics uncertainties • PSF corrections • Redshift distribution • Clustering • Contamination by overlapping galaxies • Intrinsic alignement • Intrinsic foreground/backgound correlations • Sampling variance • Non-linear variance • Non-linear dark matter power spectrum • + cosmic variance (survey size, survey topology, depth)

    14. Exploring DE as function of redshift : still far from getting wa CSLS+SNLS SNSL 5yr CSLS 5yr Deep+Wide 170/170 deg2 SNLS 5yrs Jarvis, Jain, Bernstein, Dolney 2005

    15. Breaking degeneracies with tomography

    16. Survey Filters Depth Dates Status Sq. Degrees CTIO 75 1 shallow published VIRMOS 9 1 moderate published COSMOS 2 (space) 1 moderate complete 36 4 deep complete DLS (NOAO) Subaru 30? 1? deep observing 2005? 170 5 moderate observing CFH Legacy 2004-2008 830 3 shallow approved RCS2 (CFH) 2005-2007 VST/KIDS/ VISTA/VIKING 1700 4+5 moderate 2007-2010? 50%approved 5000 4 moderate proposed DES (NOAO) 2008-2012? Pan-STARRS ~10,000? 5? moderate ~funded 2006-2012? LSST 15,000? 5? deep proposed 2014-2024? 1000+ (space) 9 deep proposed JDEM/SNAP 2013-2018? Cosmic shear: non-SKA projects KIDS + CFHTLS Wide + CFHTLS Deep: 3 lens planes proposed moderate 5000? 4+5 2010-2015? VST/VISTA proposed moderate 2+1? DUNE 20000? (space) 2012-2018?

    17. DUNE: Very Large FOV: 10000 deg2 Space: excellent PSF correction No spectro-z Reasonnably good photo-z? 109 galaxies 2017? SNAP: Reasonnable FOV: 1000 deg2 Space: excellent PSF correction No spectro-z Good photo-z 5x108 galaxies >2015? LSST: Very Large FOV: 15000 deg2 Ground: reassonably good PSF correction No-spectro-z Reasonnably good photo-z 5x109 galaxies 2014? SKA vs. others SKA: Very Large FOV: 20000 deg2 Radio: Excellent PSF correction Spectro-z 5x109 galaxies >2020?

    18. SNAP cosmic shaer: 300deg2

    19. Merit factors BUT: this assumes systematics are controled

    20. Intrinsic projected ellipticity distribution of galaxies in the optical/NIR bands σε =0.35

    21. Intrinsic projected ellipticity of SKA galaxies • What is σε for the SKA sample? • How does it vary with galaxy type? • How does it vary with environment? • How does it vary with redshift?

    22. Cosmic shear with SKA • Strong points: • Very large FOV (linear spectrum, cosmic variance) • Excellent sampling of the PSF • Excellent sampling of galaxies • Very precise N(z) :best for control of systematics (e.g. effects of clustering) • Unknown: • Intrinsic ellipticity dispersion and its evolution with redshift • PSF stability ? • Weak point: • A bit far as compared to other projects (could be an advantage… it depends on what other projects will find…)