Tests of Gaussianity of CMB maps

ABSTRACT We study two different methods to test Gaussianity in CMB maps. One of themis based on the partition function and the other on the morphology of hot and cold spots. Thepartition function contains information on all the moments and scales, being a useful quantity tocompress the large data sets expected from future space missions like Planck. In particular, itcontains much richer information than the one available through the radiation power spectrum.The second method utilizes morphological properties of hot and cold spots such as the eccentricityand number of spots in CMB maps. We study the performance of both methods in detectingnon-Gaussian features in small scale CMB simulated maps as those which will be provided by thePlanck mission.KEYWORDS: CMB anisotropy. Gaussianity. 1. INTRODUCTIONFuture CMB experiments like the Planck mission will provide very large data sets atsmall angular scales with a high sensitivity. Their analysis will require the develop-ment of new and sophisticated methods capable of managing the data, performingan optimal separation of the different components (CMB, Galactic and extragalac-tic foregrounds), extracting their statistical properties and finally determining thefundamental cosmological parameters. Two methods for foreground removal havealready been proposed based on Maximum Entropy (Hobson et al. 1998, 1999a)and Wiener filter (Tegmark and Efstathiou 1996). The power spectrum of the tem-perature fluctuations is the most widely used quantity in order to compress the dataand obtain the cosmological parameters. This quantity only carries information onthe second moment of the distribution and completely characterizes the statisticalproperties of the data if these are Gaussian distributed. However, at present there1