A Perturbative Analysis of Synchrotron Spectral Index Variation over the Microwave Sky
Rajib Saha,Pavan K. Aluri +1 more
TLDR
In this paper, a perturbative approach was proposed to estimate the spectral index variation map of synchrotron Stokes Q signal over a region of sky dominated by the synchroron signal.Abstract:
In this paper, we implement a perturbative approach, first proposed by Bouchet & Gispert (1999), to estimate variation of spectral index of galactic polarized synchrotron emission, using linear combination of simulated Stokes Q polarization maps of selected frequency bands from WMAP and Planck observations on a region of sky dominated by the synchrotron Stokes Q signal. We find that, a first order perturbative analysis recovers input spectral index map well. Along with the spectral index variation map our method provides a fixed reference index, ^ 0s, over the sky portion being analyzed. Using Monte Carlo simulations we find that,h ^ 0si = -2:84 0:01, which matches very closely with position of a peak at s(p) = -2:85, of empirical probability density function of input synchrotron indices, obtained from the same sky region. For thermal dust, mean recovered spectral index,h ^ di = 2:00 0:004, from simulations, matches very well with spatially fixed input thermal dust spectral index d = 2:00. As accompanying results of the method we also reconstruct CMB, thermal dust and a synchrotron template component with fixed spectral indices over the entire sky region. We use full pixel-pixel noise covariance matrices of all frequency bands, estimated from the sky region being analyzed, to obtain reference spectral indices for synchrotron and thermal dust, spectral index variation map, CMB map, thermal dust and synchrotron template components. The perturbative technique as implemented in this work has the interesting property that it can build a model to describe the data with an arbitrary but enough degree of accuracy (and precession) as allowed by the data. We argue that, our method of reference spectral index determination, CMB map, thermal dust and synchrotron template component reconstruction is a maximum likelihood method. Subject headings: cosmic background radiation — cosmology: observations — diffuse radiationread more
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An Improved Diffuse Foreground Subtraction by ILC method: CMB Map and Angular Power Spectrum using Planck and WMAP Observations
TL;DR: In this article, a multi-phase iterative internal-linear-combination (ILC) approach was proposed for diffuse foreground minimization from Cosmic Microwave Background (CMB) maps.
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Improved Diffuse Foreground Subtraction with the ILC Method: CMB Map and Angular Power Spectrum Using Planck and WMAP Observations
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Delta-map method of removing CMB foregrounds with spatially varying spectra
TL;DR: In this paper, the authors extended the internal template foreground removal method by accounting for spatially varying spectral parameters such as the spectral indices of synchrotron and dust emission and the dust temperature.
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An Application of the Global ILC Algorithm over Large Angular Scales to Estimate the CMB Posterior Using Gibbs Sampling
Vipin Sudevan,Rajib Saha +1 more
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A Global ILC Approach in Pixel Space over Large Angular Scales of the Sky using CMB Covariance Matrix
Vipin Sudevan,Rajib Saha +1 more
TL;DR: In this paper, a new internal linear combination (ILC) method was proposed to estimate a foreground minimized Cosmic Microwave Background (CMB) temperature anisotropy map by incorporating prior knowledge about the theoretical CMB covariance matrix.
References
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Planck 2015 results - XIII. Cosmological parameters
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TL;DR: In this article, the authors present a cosmological analysis based on full-mission Planck observations of temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation.
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Krzysztof M. Gorski,Krzysztof M. Gorski,E. Hivon,A. J. Banday,Benjamin D. Wandelt,F. K. Hansen,Mstvos Reinecke,Matthia Bartelmann +7 more
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Nine-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
Gary Hinshaw,Davin Larson,Eiichiro Komatsu,David N. Spergel,David N. Spergel,Charles L. Bennett,Joanna Dunkley,Michael R. Nolta,Mark Halpern,Robert S. Hill,N. Odegard,Lyman A. Page,Kendrick M. Smith,Kendrick M. Smith,Janet L. Weiland,B. Gold,N. Jarosik,Alan J. Kogut,Michele Limon,S. S. Meyer,Gregory S. Tucker,Edward J. Wollack,Edward L. Wright +22 more
TL;DR: In this paper, the authors present cosmological parameter constraints based on the final nine-year WMAP data, in conjunction with a number of additional cosmology data sets.
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HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
Krzysztof M. Gorski,E. Hivon,A. J. Banday,Benjamin D. Wandelt,F. K. Hansen,Martin Reinecke,M. Bartelman +6 more
TL;DR: The Hierarchical Equal Area iso-Latitude Pixelization (HEALPix) as discussed by the authors is a data structure with an associated library of computational algorithms and visualization software that supports fast scientific applications executable directly on very large volumes of astronomical data and large area surveys in the form of discretized spherical maps.
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A Generalized inverse for matrices
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