Planck 2013 Results. XXIV. Constraints on primordial non-Gaussianity

The Planck nominal mission cosmic microwave background (CMB) maps yield unprecedented constraints on primordial non-Gaussianity (NG).Using three optimal bispectrum estimators, separable template-fitting (KSW), binned, and modal, we obtain consistent values for the primordiallocal, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result f local/NL = 2.7± 5.8, f equil/NL = -42 ± 75, and f ortho/NL = -25 ± 39( 68% CL statistical). Non-Gaussianity is detected in the data; using skew-C_∫ statistics we find a nonzero bispectrum from residual point sources, and the integrated-Sachs-Wolfe-lensing bispectrum at a level expected in the ΛCDM scenario. The results are based on comprehensive crossvalidationof these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensivesuite of tests, and are confirmed by skew-C_∫, wavelet bispectrum and Minkowski functional estimators. Beyond estimates of individual shapeamplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and thus derive constraints onearly-Universe scenarios that generate primordial NG, including general single-field models of inflation, excited initial states (non-Bunch-Daviesvacua), and directionally-dependent vector models. We provide an initial survey of scale-dependent feature and resonance models. These results bound both general single-field and multi-field model parameter ranges, such as the speed of sound, c_s ≥0.02 (95% CL), in an eective fieldtheory parametrization, and the curvaton decay fraction r_D ≥0.15 (95% CL). The Planck data significantly limit the viable parameter space of theekpyrotic/cyclic scenarios. The amplitude of the four-point function in the local model τ_NL < 2800 (95% CL). Taken together, these constraintsrepresent the highest precision tests to date of physical mechanisms for the origin of cosmic structure.