Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-04-16
Astrophys.J.702:L87-L90,2009
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
4 pages, 3 figures
Scientific paper
10.1088/0004-637X/702/1/L87
We develop a new Bayesian method for estimating white noise levels in CMB sky maps, and apply this algorithm to the 5-year WMAP data. We assume that the amplitude of the noise RMS is scaled by a constant value, alpha, relative to a pre-specified noise level. We then derive the corresponding conditional density, P(alpha | s, Cl, d), which is subsequently integrated into a general CMB Gibbs sampler. We first verify our code by analyzing simulated data sets, and then apply the framework to the WMAP data. For the foreground-reduced 5-year WMAP sky maps and the nominal noise levels initially provided in the 5-year data release, we find that the posterior means typically range between alpha=1.005 +- 0.001 and alpha=1.010 +- 0.001 depending on differencing assembly, indicating that the noise level of these maps are biased low by 0.5-1.0%. The same problem is not observed for the uncorrected WMAP sky maps. After the preprint version of this letter appeared on astro-ph., the WMAP team has corrected the values presented on their web page, noting that the initially provided values were in fact estimates from the 3-year data release, not from the 5-year estimates. However, internally in their 5-year analysis the correct noise values were used, and no cosmological results are therefore compromised by this error. Thus, our method has already been demonstrated in practice to be both useful and accurate.
Eriksen Hans Kristian
Gorski Krzysztof
Groeneboom Nicolaas E.
Huey Greg
Jewell J.
No associations
LandOfFree
Bayesian analysis of white noise levels in the 5-year WMAP data does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Bayesian analysis of white noise levels in the 5-year WMAP data, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bayesian analysis of white noise levels in the 5-year WMAP data will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-465504