Probing the CMB cold spot through local Minkowski functionals

Abstract

Both the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck missions have reported an extremely cold spot (CS) centered at Galactic coordinate (l = 209°, b = −57°) in the cosmic microwave background map. We study the local non-Gaussianity of the CS by defining local Minkowski functionals. We find that the third Minkowski functional ν2 is quite sensitive to the non-Gaussianity caused by the CS. Compared with random Gaussian simulations, the WMAP CS deviates from Gaussianity at more than a 99% confidence level with a scale of R ∼ 10°. Meanwhile, we find that cosmic texture provides an excellent explanation for these anomalies related to the WMAP CS, which could be further tested by future polarization data.