Anomalous Parity Asymmetry of the Wilkinson Microwave Anisotropy Probe Power Spectrum Data at Low Multipoles

We have investigated non-Gaussianity of our early universe by comparing the parity asymmetry of the Wilkinson Microwave Anisotropy Probe ( WMAP ) power spectrum with simulations. We find that odd-parity preference of the WMAP data (2 ⩽ l ⩽ 18) is anomalous at 4-in-1000 level. We find it likely that low quadrupole power is part of this parity asymmetry rather than an isolated anomaly. Further investigation is required to find out whether the origin of this anomaly is a cosmological or a systematic effect. The data from Planck Surveyor , which has systematics distinct from WMAP , will help us to resolve the origin of the anomalous odd-parity preference.