Polarization-assisted WMAP-NVSS Cross Correlation Collaborators: K-W Ng(IoP, AS) Ue-Li Pen (CITA)...
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Transcript of Polarization-assisted WMAP-NVSS Cross Correlation Collaborators: K-W Ng(IoP, AS) Ue-Li Pen (CITA)...
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)