2007 (IPP)

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    Estimation of Primordial Spectrum with post-WMAP 3 year data
    (2007-07-14) Shafieloo, Arman; Souradeep, Tarun
    In this paper we implement an improved (error sensitive) Richardson-Lucy deconvolution algorithm on the measured angular power spectrum from the WMAP 3 year data to determine the primordial power spectrum assuming different points in the cosmological parameter space for a flat ΛCDM cosmological model. We also present the preliminary results of the cosmological parameter estimation by assuming a free form of the primordial spectrum, for a reasonably large volume of the parameter space. The recovered spectrum for a considerably large number of the points in the cosmological parameter space has a likelihood far better than a ‘best fit’ power law spectrum up to ∆χ2 eff ≈ −30. We use Discrete Wavelet Transform (DWT) for smoothing the raw recovered spectrum from the binned data. The results obtained here reconfirm and sharpen the conclusion drawn from our previous analysis of the WMAP 1st year data. A sharp cut off around the horizon scale and a bump after the horizon scale seem to be a common feature for all of these reconstructed primordial spectra. We have shown that although the WMAP 3 year data prefers a lower value of matter density for a power law form of the primordial spectrum, for a free form of the spectrum, we can get a very good likelihood to the data for higher values of matter density. We have also shown that even a flat CDM model, allowing a free form of the primordial spectrum, can give a very high likelihood fit to the data. Theoretical interpretation of the results is open to the cosmology community. However, this work provides strong evidence that the data retains discriminatory power in the cosmological parameter space even when there is full freedom in choosing the primordial spectrum.
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    CMB anisotropy power spectrum using linear combinations of WMAP maps
    (2007-06-25) Saha, Rajib; Souradeep, Tarun; Jain, Pankaj; et al.
    In recent years the goal of estimating different cosmological parameters precisely has set new challenges in the effort to accurately measure the angular power spectrum of CMB. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. Recently, a novel model-independent method for the estimation of CMB angular power spectrum solely from multi-frequency observations has been proposed and implemented on the first yearWMAP data by Saha et al. 2006. All previous estimates of power spectrum of CMB are based upon foreground templates using data sets from different experiments. However our methodology demonstrates that CMB angular spectrum can be reliably estimated with precision from a self contained analysis of the WMAP data. In this work we provide a detailed description of this method. We also study and identify the biases present in our power spectrum estimate. We apply our methodoly to extract the power spectrum from the WMAP 1 year and 3 year data.