Galactic foregrounds: Spatial fluctuations and a procedure of removal

Abstract

Present day cosmic microwave background (CMB) studies require more accurate removal of Galactic foreground emission. In this paper, we consider a way of filtering out the diffuse Galactic fluctuations on the basis of their statistical properties, namely, the power-law spectra of fluctuations. We focus on the statistical properties of two major Galactic foregrounds that arise from magnetized turbulence, namely, diffuse synchrotron emission and thermal emission from dust and describe how their power laws change with the Galactic latitude. We attribute this change to the change of the geometry of the emission region and claim that the universality of the turbulence spectrum provides a new way of removing Galactic foregrounds. We discuss and demonstrate how we can make use of our findings to remove Galactic foregrounds using a template of spatial fluctuations. In particular, we consider examples of spatial filtering of a foreground at small scales, when the separation into CMB signal and foregrounds is done at larger scales. We demonstrate that the new technique of spatial filtering of foregrounds may be promising for recovering the CMB signal in a situation when foregrounds are known at a scale different from the one under study. It can also improve filtering by combining measurements obtained at different scales.

24 pages, 12 figures, accepted to ApJ

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• Statistical Description of Synchrotron Intensity Fluctuations: Studies of Astrophysical Magnetic Turbulence
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• SPIDER: Probing the Early Universe with a Suborbital Polarimeter
• Spectrum and Anisotropy of Turbulence from Multi-Frequency Measurement of Synchrotron Polarization
• Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS HI data
• Loops and spurs: The angular power spectrum of the Galactic synchrotron background
• Polarimetric studies of magnetic turbulence with interferometer
• Supernova-regulated ISM -- V. Space- and time-correlations
• Studying Magnetohydrodynamic Turbulence with Synchrotron Polarization Dispersion
• Statistical properties of galactic CMB foregrounds: dust and synchrotron
• The unusual smoothness of the extragalactic unresolved radio background
• A Technique for Foreground Subtraction in Redshifted 21 cm Observations
• Discovery of Kolmogorov-like Magnetic Energy Spectrum in Tycho's Supernova Remnant by Two-point Correlations of Synchrotron Intensity
• Studying the local magnetic field and anisotropy of magnetic turbulence by synchrotron polarization derivative
• Diffusion of large-scale magnetic fields by reconnection in MHD turbulence
• Expected constraints on the Galactic magnetic field using PLANCK data
• The nature of non-Gaussianity and statistical isotropy of the 408 MHz Haslam synchrotron map
• Galactic Magnetic Turbulence from Radio data
• Gradient measurement of synchrotron polarization diagnostic: Application to spatially separated emission and Faraday rotation regions
• Exploring the intermittency of magnetohydrodynamic turbulence by synchrotron polarization radiation
• Statistical properties of Galactic synchrotron temperature and polarization maps -- a multi-frequency comparison
• Trans-Alfvenic Magnetohydrodynamic Turbulence in the Vicinity of Supernova Remnant Cassiopeia-A Shocks