Polarization-assisted WMAP-NVSS Cross Correlation

1. Polarization-assisted WMAP-NVSS Cross Correlation Guo Chin Liu (ASIAA) Collaborators: K-W Ng(IoP, AS) Ue-Li Pen (CITA)

2. Dark energy -- SNe Ia • Supernovae look farther/fainter than prediction by the model of universe composed by matter. • Model with three quarters of “energy”, which acceleratesthe expansion of universe, explains data very well.

3. Dark energy – Microwave Background Sky Geometry of our universe Power spectrum from CMB gives two hints for dark energy 1. 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 ISW effect

4. Dark energy – Microwave Background Sky • Observation of CMB first • peak alone does not • guarantee the existence of • dark energy. • We are living in low density universe, m0.3 Allen et al. 2002 Carlberg et al. 1997 • Hubble constant is not so small, for example, from SZ clusters measurement, H0=60-70Reese et al. 2002 Udomprasert et al 2004. m+k+=1 Spergal et al. 2007

5. Astronomical Observations for Dark Energy • Need to be sensitive on • Geometry of universe (distance vs. redshift relation) • 2. Structure formation Current used observations • Supernova type Ia : probe the geometry of universeCaution: assuming uniform intrinsic luminosity • CMB : good constraint on small curvatureCaution : no time evolution data • Large scale structure : evolution of geometry of universe and growth factor D(z) Caution: depend on CDM model for structure formation

6. 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. redshiftrelation and through its effect on the time evolution of the expansion rate.

7. 2 1 ISW Effect 1. If the potential decays between the time a photon falls into a potential well andwhen it climbs out it gets a boost in temperature ofdue to the differentialgravitational 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. E=|1-2| T/T=-2  d d/d

8. ISW Effect • Signature of dark energy • Probe of evolution of structure • Sensitive on large scale • Detection is limited by cosmic variance. Try to look forcorrelation of CMB with matter

9. Density fluctuation Form structures CMB gains energy Cross correlation of CMB with matter in local universeProposed by Crittenden & Turok (1996) • Possible tracers • NRAO VLA Sky Survey (NVSS) • Hard X-ray background(HEAO-1) • Sloan Digital Sky Survey (SDSS) • Two Micron All Sky Survey Extended Source Catalogue (2MASS XSC)

10. Previous work • 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 • Multipole l space: Afshordi et al. 2004 • Wavelet space: Viela et al. 2006, McEwen et al. 2007

11. Example of cross-correlation • The curve is sensitive on model of dark energy, bias factor, power spectrum of density perturbation, n_g(z) • Peaks at l~ few tens, less trouble on cosmic variance • Noise is dominated by CMB from recombination and reionization Douspis et al. 2008

12. First detection of the cross-correlation Correlating CMB sky to hard X-rays (HEAO-1) and radio galaxy (NVSS) wiNiwjTj/wiwj 3 sigma detection for hard X-rays and 2.5 sigma for radio galaxy Boughn & Crittenden, nature, 2004

13. CMB anisotropies & polarization on large scales CMB last scattering surface △TSW, z=1100 Generate P. △Treion, z=10 Generate P. △TISW, z<2 Dark energy dominates Observer

14. Correction by the information of polarization At large scales T=TSW + Tre+ TISW Eno ISW =aTno ISW + n <TE>noisw = a <TT>noisw <EE>noisw=a2<TT>noisw + n2 No ISW above T(ISW) =T – Enoisw/a * WF WF=a2<TT>/<EE> <TT>, <EE> and <TE> are obtained by CMBfast, forcing ISW=0

15. Applying to CMB power spectrum Total Polarization corrected ISW

16. Details of this work • We work at harmonic spaceSZ and radio emission is ignorable.Low correlation between each mode • Using NVSS as matter distribution tracer. • ClNW=<aNlmaT*lm>△T/T()=aTlmYlm() • Healpix software is used forvisualization and calculating alm

17. NVSS data 1. 1.4GHz , 82% sky coverage (>-40) 2. Sensitivity 2.5 mJy contains 1.8 million sources 3. Typical luminosity function models indicate 0z2 distribution

18. CMB SKY 61GHz 41GHz T T T Q Q Q U U U

19. Result • Using polarization information narrows down the uncertainties from primary CMB about 3-7% • 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

20. Summary • Working in harmonics space, signal with 2-sigma is detected in l~ 10-20. • Primary CMB is the dominated noise in this cross-correlation. Using polarization information, we can filter out part of it. • It suppress the noise about 3--7% in band power, giving a better constrain on dark energy model.

21. Contamination • Sunyaev-Zeldovich Effect: anisotropies generated through the inverse Compton scattering with free e- correlates with the galaxy itself. On small scales • Emission from the radio galaxyEmission at f<few tens GHz contaminates the microwave sky. On small scales • Primary CMB itself: △T(ISW) < 30% of △T(total)