Non-Gaussianity of diffuse Galactic synchrotron emission at 408 MHz

Abstract

Diffuse Galactic emission at low frequencies is a major contaminant for studies of redshifted $21$ cm line studies. Removal of these foregrounds is essential for exploiting the signal from neutral hydrogen at high redshifts. Analysis of foregrounds and its characteristics is thus of utmost importance. It is customary to test efficacy of foreground removal techniques using simulated foregrounds. Most simulations assume that the distribution of the foreground signal is a Gaussian random field. In this work we test this assumption by computing the binned bispectrum for the all-sky $408$ MHz map. This is done by applying different brightness temperature ($T$) thresholds in order to assess whether the cooler parts of the sky have different characteristics. We find that regions with a low brightness temperature $T<25$ K indeed have smaller departures from a Gaussian distribution. Therefore, these regions of the sky are ideal for future H{\sc i} intensity mapping surveys.

11 pages, 10 figures. Accepted for publication in the MNRAS

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• The bispectrum of polarized galactic foregrounds
• Full-sky, arcminute-scale, 3D models of Galactic microwave foreground dust emission based on filaments
• Morphological Analysis of the Polarized Synchrotron Emission with WMAP and Planck
• The nature of non-Gaussianity and statistical isotropy of the 408 MHz Haslam synchrotron map
• Morphology of CMB fields -- effect of weak gravitational lensing
• Statistical properties of polarized CMB foreground maps
• Statistical properties of Galactic synchrotron temperature and polarization maps -- a multi-frequency comparison
• A Novel Bispectrum Estimator of the Kinematic Sunyaev-Zel'dovich Effect using Projected Fields