Local properties of Wilkinson Microwave Anisotropy Probe cold spot

Abstract

We investigate the local properties of WMAP Cold Spot (CS) by defining the local statistics: mean temperature, variance, skewness and kurtosis. We find that, compared with the \emph{coldest spots} in random Gaussian simulations, WMAP CS deviates from Gaussianity at $\sim 99%$ significant level. In the meanwhile, when compared with the spots at the same position in the simulated maps, the values of local variance and skewness around CS are all systematically larger in the scale of $R>5^{\circ}$, which implies that WMAP CS is a large-scale non-Gaussian structure, rather than a combination of some small structures. This is consistent with the finding that the non-Gaussianity of CS is totally encoded in the WMAP low multipoles. Furthermore, we find that the cosmic texture can excellently explain all the anomalies in these statistics.