IUCAA Preprints
Permanent URI for this communityhttp://localhost:4000/handle/11007/149
Browse
2 results
Search Results
Item 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.Item CMB Polarization and Temperature Power Spectra Estimation using Linear Combination of WMAP 5-year Maps(2009-03-01) Souradeep, Tarun; Jain, Pankaj; Saha, Rajib; et al.We estimate CMB polarization and temperature power spectra using WMAP 5-year foreground contaminated maps. The power spectrum is estimated by using a model independent method, which does not utilize directly the diffuse foreground templates nor the detec tor noise model. The method essentially consists of two steps, (i) removal of diffuse foregrounds contamination by making linear combination of individual maps in harmonic space and (ii) cross-correlation of foreground cleaned maps to minimize detector noise bias. For temperature power spectrum we also estimate and subtract residual unre- solved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our 1TT, TE and EE power spectra are in good agreement with the published results of the WMAP science team. The error bars on the polarization power spectra, however, turn out to be smaller in comparison to what is obtained by the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We find that the bias is small in all cases. A negative bias at low l in TT power spectrum has been pointed in an earlier publication. We find that the bias corrected quadrupole power (l(l + 1)Cl/2π) is 532 µK2, approximately 2.5 times the estimate (213.4 µK2) made by the WMAP team.