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The decomposition of a signal on the sphere with the steerable wavelet constructed from the second Gaussian derivative gives access to the orientation, signed-intensity and elongation of the signal's local features. In the present work, the non-Gaussianity of the Wilkinson Microwave Anisotropy Probe ( WMAP) temperature data of the cosmic microwave background (CMB) is analysed in terms of the first four moments of the statistically isotropic random fields associated with these local morphological measures, at wavelet scales corresponding to angular sizes between 27.5 arcmin and 30° on the celestial sphere. While no detection is made either in the orientation analysis or in the elongation analysis, a strong detection is made in the excess kurtosis of the signed-intensity of the WMAP data. The non-Gaussianity is observed with a significance level below 0.5 per cent at a wavelet scale corresponding to an angular size around 10°, and confirmed at neighbouring scales. This supports a previous detection of an excess of kurtosis in the wavelet coefficient of the WMAP data with the axisymmetric Mexican hat wavelet. Instrumental noise and foreground emissions are not likely to be at the origin of the excess of kurtosis. Large-scale modulations of the CMB related to some unknown systematics are rejected as possible origins of the detection. The observed non-Gaussianity may therefore probably be imputed to the CMB itself, thereby questioning the basic inflationary scenario upon which the present concordance cosmological model relies. Taking the CMB temperature angular power spectrum of the concordance cosmological model at face value, further analysis also suggests that this non-Gaussianity is not confined to the directions on the celestial sphere with an anomalous signed-intensity. [ABSTRACT FROM AUTHOR]

The Australia Telescope 20-GHz (AT20G) Survey is a blind survey of the whole southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried out with the Australia Telescope Compact Array from 2004 to 2007. The Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G Survey catalogue comprising 320 extragalactic ) radio sources south of with Jy. Of these, 218 have near simultaneous observations at 8 and 5 GHz. In this paper we present an analysis of radio spectral properties in total intensity and polarization, size, optical identifications and redshift distribution of the BSS sources. The analysis of the spectral behaviour shows spectral curvature in most sources with spectral steepening that increases at higher frequencies (the median spectral index α, assuming , decreases from between 4.8 and 8.6 GHz to between 8.6 and 20 GHz), even if the sample is dominated by flat spectra sources (85 per cent of the sample has . The almost simultaneous spectra in total intensity and polarization allowed us a comparison of the polarized and total intensity spectra: polarized fraction slightly increases with frequency, but the shapes of the spectra have little correlation. Optical identifications provided an estimation of redshift for 186 sources with a median value of 1.20 and 0.13, respectively, for QSO and galaxies. [ABSTRACT FROM AUTHOR]