Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

未来 の 暗 黒 エネルギー 実験 の 相補性

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

Complementarity of Future Dark Energy Probes

Jiayu Tang, Filipe Abdalla and JW

(DETF::UCL)

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

What would we like to learn from a Dark Energy experiment?• Possible ‘explanations’ of observed accelerated

expansion:1. extra energy component in the Universe (see Copeland)2. modification of gravity on large scales (see Maartens)3. 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.

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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,, ...

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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)?

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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)

Mode becomes negative here

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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)

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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

Jochen Weller

Decrypting the UniverseEdinburgh, October, 2007

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, ...)