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未来 の 暗 黒 エネルギー 実験 の 相補性

未来 の 暗 黒 エネルギー 実験 の 相補性. Complementarity of Future Dark Energy Probes. Jiayu Tang , Filipe Abdalla and JW (DETF::UCL). What would we like to learn from a Dark Energy experiment?. Possible ‘explanations’ of observed accelerated expansion: extra energy component in the Universe (see Copeland)

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未来 の 暗 黒 エネルギー 実験 の 相補性

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  1. 未来の暗黒エネルギー実験の相補性

  2. Complementarity of Future Dark Energy Probes Jiayu Tang, Filipe Abdalla and JW (DETF::UCL)

  3. What would we like to learn from a Dark Energy experiment? • Possible ‘explanations’ of observed accelerated expansion: • extra energy component in the Universe (see Copeland) • modification of gravity on large scales (see Maartens) • inhomogeneous Universe - acceleration effect of averaging procedure • Key Question: Different from cosmological constant? • unique feature of : energy density constant • test if energy density varies with time (redshift, scale factor) • effectively looking for “w=p/”; of course not really physical meaning for 2. and 3.

  4. Parameterizations of Dark Energy • Background evolution • w = w0 • w = w0+w1z • w = w0+ ln(a) (Efstathiou 1999) • w = w0+wa(1-a) (Chevalier 2001, Linder 2003) • binned w(z) (‘parameter free’) • Perturbations: cs2,, ...

  5. Binning of w(z) • use 50 (large number) bins • zmax given by particular survey • effectively parameter free • continuous binning required for including CMB (Crittenden & Pogosian 2005) • Fiducial model: w = -0.9 constant

  6. Principal Component Analysis • Calculate Fisher matrix for leading order approximation of Likelihood • Diagonalize Fisher matrix do establish independent modes • Decompose w(z) in Eigenmodes • Inverse of eigenvalue is measure of uncertainty in Eigenmode (j = j-1/2), Eigenmode reflects redshift sensitivity of survey • (Huterer and Starkman 2003; Crittenden & Pogosian 2005) • Going beyond DETF figure of merit and pivot redshift

  7. Analysis with Principal Components • Establish leading components via Fisher matrix • Estimate coefficients with MCMC or full likelihood (may need to iterate fiducial model)(Huterer and Peiris, 2007) • How about priors on Eigenmodes? • How to establish number of modes to take along (risk, likelihood ratio, F-test, evidence)?

  8. Future Observations (very subjective) • South Pole Telescope: 1000 element Bolometer Array; 4,000 deg2; 150,250 and 270 GHz; 10m telescope; 1’ beam; deployed begining of 2007. • PanStarrs: photo-z; z=0-1; >30,000 deg2; 23.8 mag; griz and y filter and wide band (g+r+i); 4 cameras at PS4 on 1.8m mirror (1.4 billion pixels) (see Phleps talk). • Dark Energy Survey: Imaging Survey on 4m Blanco; 5,000 deg2 sky coverage; 24mag in griz+VISTA IR; photo-z; z=0.35-1.39 (see Lahav talk) • WFMOS: Spectrograph on Gemini (Subaru) telescope, limiting m=24, wide survey: 2000 deg2, z = 0.5-1.3; deep survey: 300 deg2, z = 2.3 - 3.3 (see Parkinson/Miyazaki talk) • DUNE: Satellite; Imaging survey, photo-z; z=0.1-1.1, half sky, one wide (r+i+z) band and NIR; mag limit 24.5; ground based complement (see Refregier talk) • SNAP: Satellite; 6 optical + 3 NIR filters; z=0-1.7, 300 deg2 WL

  9. Mode becomes negative here Supernovae Probes • Measure of redshift - distance relation • SNAP: 3000 SNe • Most weight at redshift z=0.2 (DE domination) • Modes above 3rd are very weakly constrained (1 = 0.14; 2 = 0.30; 3 = 0.55)

  10. Comparison of SNe probes • DES: 1,900 SNe (1 = 1.26; 2 = 3.46) • PanStarrs: 6,000 SNe (1 = 0.13; 1 = 0.28) • SNAP and PanStarrs very similar

  11. Weak Lensing Probes • Probing expansion and growth of structure • DES: zmax = 2.0; = 0.34 • Leading Principal Components reflect redshift bins • Strong constraints at z=0.3 and z=1.0 • 1 = 0.25; 2 = 2.95; 3= 3.93

  12. Comparison of WL probes • Use simulated galaxy redshift distributions (DES: Huan Lin, DUNE: Peter Capak) • SNAP 2-bins: zmax = 3.0; =0.31 (1 = 1.67; 2 = 5.91) • SNAP 3-bins: (1 = 0.39; 2 = 2.37) • DES 1-bin: (1 = 50.0; 2 = 78.0) • DES 3-bins: (1 = 0.25; 2 = 2.95) • DUNE 1-bin: zmax = 3.0; =0.40 (1 = 24.9; 2 = 33.7) • DUNE 5-bins: (1 = 0.0053; 2 = 0.031)

  13. Baryon Acoustic Oscillations • Measure of angular diameter distance • Combination of wide and deep WFMOS survey. • kmax = 0.15 cut-off • Peak constraint above z=0.5! • 1 = 0.17; 2 = 0.53; 3= 0.66

  14. Sunayev-Zel’dovich Galaxy Cluster Counts • Measure of growth and volume • zmax = 1.5 • Peak below z=0.5 • 1 = 0.39; 2 = 0.96; 3= 1.55

  15. Effects of Other Cosmological Parameters • Other cosmological parameters (m, H0,M,...) • Marginalize Fisher matrix over extra parameters and then calculate principal components • sign of mode changes above z=0.5 • peak of modes shifts to lower redshift • so far no priors on w • conservative (-1<w<-1/3) • smoothness

  16. Comparing Different Surveys • Clearly WL (from DUNE) is best constraint for z<1, while BAO is most promising for larger redshifts, however these are Stage IV (DETF) missions • Galaxy cluster number counts not as good as SNe (but are forthcoming data sets) and are at Stage II-III. • More to come ... (ADEPT, PANSTARRS WL, ...)

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