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 primordial local, 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 ℓ 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 crossvalidation of these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are confirmed by skew-C ℓ , wavelet bispectrum and Minkowski functional estimators.Beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and thus derive constraints on early-Universe scenarios that generate primordial NG, including general single-field models of inflation, excited initial states (non-Bunch-Davies vacua), 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 effective field theory parametrization, and the curvaton decay fraction r D ≥ 0.15 (95% CL).The Planck data significantly limit the viable parameter space of the ekpyrotic/cyclic scenarios.The amplitude of the four-point function in the local model τ NL < 2800 (95% CL).Taken together, these constraints represent the highest precision tests to date of physical mechanisms for the origin of cosmic structure.