1. WMAP 5 year

Posted by Dmitry
March 6, 2008

Clearly, the most important paper(s) in astro-ph today is the release of the 5 year data of WMAP. The references to papers are:

  1. “Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation”
  2. “Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Beam Maps and Window Functions”
  3. “The Wilkinson Microwave Anisotropy Probe (WMAP) Source Catalog”
  4. “Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Likelihoods and Parameters from the WMAP data”
  5. “Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Angular Power Spectra”
  6. “Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission”
  7. “Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results”

If you do not know what is WMAP :)

It is NASA satellite mission with the goal to measure the temperature of the cosmic microwave background radiation (CMB). It measures the CMB temperature and its fluctuations over the all sky with angular resolution 0.3 degrees and sensitivity about 20 microKelvin er 0.3 degrees.

The WMAP sattelite was launched on 30 June 2001, first set of data was released in 2003 and the second set - in 2006 (dataset is supposed to be released every two years, and this one was seriously delayed forcing us to think that the WMAP team found something extraordinary :)). Already 2003 data greatly exceeded the old CMB data in accuracy, so 30 June 2001 is considered by many as the beginning of the era of precision cosmology. This data release is the third one.

In this respect, the WMAP project is of extreme significance; thanks to WMAP data, many cosmological parameters are known today with rather high precision.

5 year data and cosmological parameters

Now, I will take for granted that you know what are the cosmological parameters such as \Omega . If you do not, feel free to ask in comments.

So, what are the results of the 5th year compared to the 3rd year? 5 year data limit the deviation from the minimal Lambda Cold Dark Matter model (LCDM) even more strongly.

As follows from WMAP data combined with the Type IIA supernovae and BAO (Baryon Acoustic Oscillations) measurements, parameters of LCDM are:

1.\Omega_b=0.0462\pm 0.0015,

2. \Omega_m=0.233\pm 0.013, ,

3.\Omega_\Lambda=0.721\pm 0.015,

4. H_0=70.1\pm 1.3 km/s/Mpc,

5. n_s=0.960+0.014-0.013, positive spectral index is slightly more favored,

6. r<0.20 at the 95% confidence level. WMAP 5 year data alone improve the upper bound for r to 0.43 at the same confidence level,

7. effective equation of state for the dark energy is constrained as -0.38<1+w_0<0.14 at the 95% confidence level,

8. -9<f_{NL}^{local}<111, -151<f_{NL}^{equil}<253 at the 95% confidence level, so Yadav-Wandelt conclusion regarding primordial non-gaussianity does still look much stronger :)

9. \tau=0.084\pm 0.016. With 5 years of polarization data, the optical depth is measured at 5 sigma significance.

The overall conclusion is a spatially flat universe dominated by the dark energy; primordial fluctuations are adiabatic and nearly scale-invariant Gaussian. No surprises…

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Cosmology, Master Postdoc

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2 Comments »

Comment by Instanton
2008-03-11 10:22:00

Hello

From your post I did not get it - what is the improvement compared to 3Y data ?

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Comment by Dmitry
2008-03-11 10:57:02

Dear Instanton
Thanks for visiting my blog. I am going to write an additional post on WMAP results, hope it will make the issue :) clearer.
Dmitry.

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