Polarization-assisted WMAP-NVSS Cross

Correlation

Collaborators: K-W Ng(IoP, AS) Ue-Li Pen (CITA)

Guo Chin Liu (ASIAA)

Dark energy -- SNe Ia

1. Supernovae look

farther/fainter than

prediction by the model of

universe composed by

matter.

2. Model with three quarters of

“energy”, which accelerates

the expansion of universe,

explains data very well.

Dark energy – Microwave Background Sky Geometry of our universe

ISW effect

Power spectrum from CMBgives two hints for darkenergy1. Position of first peak

proves the curvature of our universe is small

2. The enhancement on large-scale may prove the existence of dark energy

Spergal et al. 2007

Observation of CMB firstpeak alone does notguarantee the existence ofdark energy.1. We are living in low

density universe, m0.3 Allen et al. 2002Carlberg et al. 1997

2. Hubble constant is not so small, for example, from SZ clusters measurement, H0=60-70

Reese et al. 2002Udomprasert et al 2004.

m+k+=1

Dark energy – Microwave Background Sky

Astronomical Observations for Dark EnergyNeed to be sensitive on1. Geometry of universe (distance vs. redshift relation)

2. Structure formation

1. Supernova type Ia : probe the geometry of universeCaution: assuming uniform intrinsic luminosity

2. CMB : good constraint on small curvatureCaution : no time evolution data

3. Large scale structure : evolution of geometry of universe and growth factor D(z) Caution: depend on CDM model for structure formation

Current used observations

Future observation

Weak lensing: Size of distortion image depends on distance traveled and growth factor

BAO: Baryon Acoustic Oscillation is sensitive to dark energy through its effect on the angular-diameter distance vs. redshift relation and through its effect on the time evolution of the expansion rate.

1. If the potential decays between the time a photon falls into a potential well and when it climbs out it gets a boost in temperature of due to the differential gravitational redshift and due to an accompanying contraction of the wavelength

2. No ISW effect in matter dominate epoch.

3. The dark energy dominating on late epoch creates the

temperatures anisotropies on large scales.

12

E=|1-2|

T/T=-2 d d/d

ISW Effect

1. Signature of dark energy

2. Probe of evolution of structure

3. Sensitive on large scale

4. Detection is limited by cosmic

variance.

Try to look for correlation of CMB with matter

ISW Effect

Cross correlation of CMB with matter in local universe

Proposed by Crittenden & Turok (1996)

Possible tracers1. NRAO VLA Sky Survey (NVSS)2. Hard X-ray background (HEAO-1)3. Sloan Digital Sky Survey (SDSS)4. Two Micron All Sky Survey Extended Source Catalogue

(2MASS XSC)

Density fluctuation

CMB gains energyForm structures

1. Real space : Diego et al. 2003, Boughn & Crittenden

2004, Cabre et. al. 2006, Nolta et al. 2004, Giannantonin

et al. 2006, Rassat et al. 2006

2. Multipole l space: Afshordi et al. 2004

3. Wavelet space: Viela et al. 2006, McEwen et al. 2007

Previous work

1. The curve is sensitive on model of

dark energy, bias factor, power

spectrum of density perturbation,

n_g(z)

2. Peaks at l~ few tens, less trouble

on cosmic variance

3. Noise is dominated by CMB from

recombination and reionization

Example of cross-correlation

Douspis et al. 2008

First detection of the cross-correlation

Boughn & Crittenden, nature, 2004

Correlating CMB sky to

hard X-rays (HEAO-1) and

radio galaxy (NVSS)

wiNiwjTj/wiwj

3 sigma detection for hard

X-rays and 2.5 sigma for

radio galaxy

△ TSW, z=1100

△ Treion, z=10

△ TISW, z<2

ObserverDark energy dominates

Generate P.

CMB last scattering surface

Generate P.

CMB anisotropies & polarization on large scales

Correction by the information of polarization

Eno ISW =aTno ISW + n<TE>noisw = a <TT>noisw

<EE>noisw=a2<TT>noisw + n2

No ISW above

T(ISW) =T – Enoisw/a * WFWF=a2<TT>/<EE>

At large scales T=TSW + Tre + TISW

<TT>, <EE> and <TE> are obtained by CMBfast, forcing ISW=0

Applying to CMB power spectrum

ISW

Total

Polarization corrected

Details of this work

1. We work at harmonic spaceSZ and radio emission is ignorable.Low correlation between each mode

2. Using NVSS as matter distribution tracer.

3. ClNW=<aN

lmaT*lm>

△T/T()=aTlmYlm()

4. Healpix software is used for

visualization and calculating alm

NVSS data

1. 1.4GHz , 82% sky coverage (>-40)2. Sensitivity 2.5 mJy contains 1.8 million sources3. Typical luminosity function models indicate 0z2 distribution

61GHz41GHz

T T

Q Q

U U

CMB SKY

T

Q

U

Result1. Using polarization

information narrows down

the uncertainties from

primary CMB about 3-7%

2. Better instrument noise

estimation is necessary

(mainly from 1/f)

Error bars are obtained by correlation of 500 simulated CMB maps with real NVSS data

Summary

1. Working in harmonics space, signal with 2-sigma is detected

in l~ 10-20.

2. Primary CMB is the dominated noise in this cross-correlation.

Using polarization information, we can filter out part of it.

3. It suppress the noise about 3--7% in band power, giving a

better constrain on dark energy model.

Contamination

1. Sunyaev-Zeldovich Effect: anisotropies generated through

the inverse Compton scattering with free e- correlates with

the galaxy itself.

On small scales

2. Emission from the radio galaxy

Emission at f<few tens GHz contaminates the microwave

sky.

On small scales

3. Primary CMB itself: T(ISW)△ < 30% of △T(total)