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 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

Spergal et al Observation of CMB first peak alone does not guarantee the existence of dark energy. 1.We are living in low density universe,  m  0.3 Allen et al Carlberg et al Hubble constant is not so small, for example, from SZ clusters measurement, H 0 =60-70 Reese et al Udomprasert et al  m +  k +   =1 Dark energy – Microwave Background Sky

Astronomical Observations for Dark Energy Need to be sensitive on 1.Geometry of universe (distance vs. redshift relation) 2. Structure formation 1.Supernova type Ia : probe the geometry of universe Caution: assuming uniform intrinsic luminosity 2.CMB : good constraint on small curvature Caution : 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. 11 22  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 tracers 1.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 energy Form 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 Multipole l space: Afshordi et al Wavelet space: Viela et al. 2006, McEwen et al 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)  w i  N i w j  T j /  w i w j 3 sigma detection for hard X-rays and 2.5 sigma for radio galaxy

△ T SW, z=1100 △ T reion, z=10 △ T ISW, z<2 Observer Dark energy dominates Generate P. CMB last scattering surface Generate P. CMB anisotropies & polarization on large scales

Correction by the information of polarization E no ISW =aT no ISW + n noisw = a noisw noisw =a 2 noisw + n 2 No ISW above T (ISW) =T – E noisw /a * WF WF=a 2 / At large scales T=T SW + T re + T ISW, and 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 space SZ and radio emission is ignorable. Low correlation between each mode 2.Using NVSS as matter distribution tracer. 3.C l NW = △ T/T(  )=  a T lm Y lm (  ) 4.Healpix software is used for visualization and calculating a lm

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

61GHz 41GHz T T Q Q UU CMB SKY T Q U

Result 1.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~ 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)