how can cmb help constraining dark energy? licia verde icrea & institute of space sciences (ice...

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How can CMB help constraining dark energy?

Licia VerdeICREA & Institute of space Sciences (ICE CSIC-IIEC)




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Interpretation key:

Black background: background material/work by others

White background: work I am directly involved with/my biased view

The standard cosmological model

Spatially flat Universe QuickTime™ and aTIFF (LZW) decompressor


Power-law, primordial power spectrum

Only 6 parameters: WMAP5yr analysis

CDM model





Survived 15 years of data!







Dark energy from CMB

2dfGRS

H prior

WMAPII

SN

With DE clusteringWMAP3



Dark energy



WMAP5

Komatsu et al (2008)

Why so weak dark energy constraints from CMB?



WMAP5

Dunkley et al (2008)



If I wanted to reconstruct non parametrically V

Theoretical physicists: which parameterization?

To give you a flavor, assume it is a slowly rolling potential and think about inflation

Similar to horizon flow parameters (from Simon et al 2005; Fernandez-Martinez & LV ‘08)





H(z)

H(z)

Just integrate to get(z)

You need to have a parameterization (or a model)QuickTime™ and a

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Can be integrated analytically!



No single observation that I know of can give this

Why so weak dark energy constraints from CMB?

The limitation of the CMB in constraining dark energy is that the CMB is located at z=1090.

We need to look at the expansion history (I.e. more than one snapshot of the Universe)



WMAP5Dunkley et al (2008)

Several options….

THE SYMPTOMSOr OBSERVATIONAL EFFECTS of DARK ENERGY

Recession velocity vs brightness of standard candles: dL(z)

CMB acoustic peaks: Da to last scattering

LSS: perturbations amplitude today, to be compared with CMB

Da to zsurvey

Perturbation amplitude at zsurvey

Leading observational techniques to go after dark energy

Supernovae

Baryonic Acoustic Oscillations (BAO)

Weak Lensing

Galaxy clusters number counts

(expansion history)

(expansion history)

(growth of structure and expansion history)

(mostly growth of structure)

Q: A combination of techniques will be best for at least two reasons

What if one could see the peaks pattern also at lower redshifts?

weak dark energy constraints from CMB?

BUT The CMB encloses information about the growth of foreground structures: secondary CMB!

Integrated Sachs Wolfe effect

Secondary effects: Sunyaev Zeldovich(SZ), Kintetic SZ, Rees-Sciama, Lensing.

A

B

C … resort to other probes

(and get other things for free)


Take the “concordance approach”

CMB offers an anchor point at a time where Dark energy is unimportant

..or is it?

Acquaviva & LV 2007 considered a Brans-Dickie model,which looks like L at late times and which has virtually the same Growth of structure as LCDM

Example: If you try to “hide” Dark Energy…

Still shows up in the concordance approach….





BUT The CMB encloses information about the growth of foreground structures: secondary CMB!


Secondary effects: Sunyaev Zeldovich(SZ), Kintetic SZ, Rees-Sciama, Lensing. (cross correlations!)

A

B



USE the CMB as BACKLIGHT, illuminating the foreground universe

High z mid z low z

• First galaxies • Universe is reionized• Ostriker-Vishniac• Diffuse thermal SZ

• Cluster formation: Sunyaev-Zel’dovich (SZ)• Kinematic SZ• Lensing of the CMB

• The growth of structure is sensitive to dark energy• Rich additional science from correlations among effects

• Extraction of cosmological parameters• Initial conditions for structure formation

Sunyaev-Zel’dovich (SZ) clusters

e-

e-

e-

e-

e-

e-

e-

e-

e-

Coma Cluster Telectron = 108 K

Optical: Redshift and Mass

mm-Wave: SZ –Compton Scattering

X-ray Flux: Mass



http://www.physics.princeton.edu/act/

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Barcelona, Cardiff, Columbia, Haverford, Inaoe, KwaZulu-Natal, NASA, NIST,UPenn,Princeton, U. Pittsburgh, Rutgers, Toronto, UBC, Cape Town, Universidad Catolica, York College



The south pole telescope





http://pole.uchicago.edu/public/ QuickTime™ and aTIFF (Uncompressed) decompressor


19

Kinetic SZ/Ostriker-Vishniac (OV)

Non-Gaussian but with CMB frequency spectrum. Spatially distinguishable. Requires a high fidelity map.

Amplitude of OV signal determines epoch of reionization.

OV power spectrum measures the density and velocity fluctuations at reionization.

Bulk velocity of HOT electrons from ionization by the first stars (OV) or in clusters and filaments (KSZ).

ve

Bulk Velocity of hot electrons.

CMB photon

KSZ measures cluster bulk velocity field at low z.



Velocities: using the KSZ signal





W=-1.0

W=-0.6

(Hernandez-Monteagudo, LV, Jimenez, Spergel 2006)

The peculiar velocity field is sensitive to the onset of the late acceleration of the Universe.

Recall that KSZQuickTime™ and a

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Narrow and deep

Wide and shallow

...++Δ

+Θ∇•Δ

+Δ

≅Δ

SZTT

TT

TT

TT NLPP

γ

Lensing

∫ Φ−

−=Θ*

0 *

* ),(2)(r

drrrrr

rrγγ

drrrtT

T NLNL

),(2 γΦ∂∂

=Δ

∫

Rees-Sciama

Low z(high l )

High z (low l )

Depends on w,0Ω

Gravitational potential

Lensing and Rees-SciamaLensing and Rees-Sciama(LV, Spergel 2002)

ISW, but non-linear



Bispectrum :

to couple the high z universe (low ) to the low z universe (high ) via the weak lensing signal

Balance of 2 competing contributions:

=>Decay of gravitational potential (non Einstein de Sitter Universe)

=>Amplification due to non-linear gravitational evolution

Balance depends on Ωm and w

321

3

3

2

2

1

1

321

321

321

321lllllllll

lllB

mmmaaaB mmmmmm

⎟⎟⎠

⎞⎜⎜⎝

⎛==

ll

Consider primordial, lensing & Rees-Sciama:

(Verde, Spergel 2002)

Bispectrum: Cross correlating primordial-lensing-Rees Sciama

Forecast: ACT+WMAP data

Fiducial model

See also Giovi Baccigalupi, Perrotta 2004 for w(z)



BUT The CMB encloses information about the growth of foreground structures: secondary CMB


Secondary effects: Sunyaev Zeldovich(SZ), Kintetic SZ, Rees-Sciama, Lensing.

A

B



Investment portfolio



Investment portfolio



Low risk investment

Medium risk, medium gain

High risk, high potential for return

Cosmic clocks: with D. Stern, M. Kamionkowski, R. Jimenez,T. Treu






are needed to see this picture.QuickTime™ and a


+GDDS



- - -WMAP3+SDSS+HST

+H(z)

GDDS +high z radiogalaxies + Treu et al. 2000 sample

From Simon, Verde, Jimenez (2005)

After tornado, earthquakes, tsunami warnings and fires…. we got data! Watch this space…

Simon et al 05Assumes Flatness



Fernandez-Martinez & LV 08Relaxing priors including flatness

Forecast: need ~1000 high resolution spectra

2 measurements in one?

Challenge: scale of interest ~100 Mpc/h: large volumes!

Feature: measure BOTH dA and H(z) from 3D clustering

Line of sight (radial)

Plane of the sky (angular)



Pau collaboration. (2008)

Spectroscopy or photometry?

AAOmega

600K galaxies, z~1 (10% error on w)

WFMOS several million galaxies >2012

VISTA, DES, LSST




are needed to see this picture.Degrade information in the z direction but is faster & can cover more sky

The debate is still open!

Could do weak lensing almost for free



PAU: Physics of the Accelerating Universe

Awarded consolider-ingenio 2010, E. Fernandez, PI

Survey ~10000 deg2 0.1<z<1.0, ~14M LRG galaxies, 100’s M total

“Hybrid” technique: narrow band photometry (the best of both worlds?)

Likely: dedicated telescope. New camera (~40 narrow band filters)

Instituto de fisica de alta energias (IFAE-Barcelona)Instituto de ciencias del Espacio (ICE-Barcelona)Instituto astrofisico de Andalucia (IAA-Granada)Instituto de fisica teorica (IFT-Madrid)Centro de investigaciones[…] (CIEMAT-Madrid)Instituto de fisica corpuscolar (IFIC -Valencia)Puerto de informacion Cientifica(PIC-Barcelona)

Close collaboration between particle physicists (theorists and experimentalists) and astrophysicists (theorists and observers)

Measures both H(z) and Da(z)

http://www.ice.csic.es/research/PAU/PAU-welcome.html

goal

goal

goal





Bruzual & Charlot11 Gyr @ z=0.2

THE IDEA:

New photometric system



Courtesy of A. Fernandez-Soto





ALHAMBRA

Courtesy of A. Fernandez-Soto





Bruzual & Charlot11 Gyr @ z=0.2

THE IDEA:

New photometric system

What filters? How?

Redshift error degradation

Feature width~15Mpc (comoving)QuickTime™ and a


Radial direction H(z) Plane of sky direction Da



1M halos,

M>3.7d13Msol

MICE simulation

27 (Gpc/h)^3

PAU collab. 2008





+ other science: galaxy formation and evolution, accurate measurement of P(k) and growth through higher-order correlations, primordial non gaussianity, metalicity for halo stars), etc…

A mine of information for studying galaxy formation!

Example: Clustering of peaks (DM halos) of a non-gaussian density field



Dalal et al 08; Matarrese, Verde 2008

fNL=100



General non-gaussianity

ΦxxfNLxxIF as motivated by inflation, then

Summary: Much ado about nothing

Observations indicate that nothing weighs something (but much less than expected) and make the universe accelerate (other options are still Possible, inhomogeneities, gravity, but the result must “look like ”).

Heroic observational effort is on going(we’ll learn not only about dark energy from it)

We HAVE TO ask: “how interesting it is really to add yet another significant figure to or w ?”

What would it take to discriminate?discuss

discuss

My personal view: The answer lies in the interface between Astronomy and Theoretical physics, if we take the“Accelerating universe challenge”, there is no other way.

The standard cosmological model is extremely successful, but….



Challenges of the accelerating universe:Zero-th order challenge: create a new culture of particlephysicists and astronomers working together, theorists and experimentalists

First_order challenge: If it is why is it so small? On this issue astronomers have done their work already (I.e. is non zero)Now it is the job of theoretical physicists.

Second order challenge: is it dynamical? and if so how does it evolve?

Third order challenge: “could we have been wrong all along?”did Einstein had the last word on gravity? Or FRW on the metric?

The data challenge: Avalanche of data coming soon The systematics challenge: systematic errors in many cases will be the limit

“In the middle of difficulty lies opportunity" --- A. Einstein

how can cmb help constraining dark energy? licia verde icrea & institute of space sciences (ice...

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