Year: 2015
Type: article
Abstract: Cosmological constraints are usually derived under the assumption of a six-parameter $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ theoretical framework or simple one-parameter extensions. In this paper we present, for the first time, cosmological constraints in a significantly extended scenario, varying up to 12 cosmological parameters simultaneously, including the sum of neutrino masses, the neutrino effective number, the dark energy equation of state, the gravitational wave background and the running of the spectral index of primordial perturbations. Using the latest Planck 2015 data release (with polarization), we found no significant indication for extensions to the standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ scenario, with the notable exception of the angular power spectrum lensing amplitude, ${A}_{\text{lens}}$, which is larger than the expected value at more than 2 standard deviations, even when combining the Planck data with BAO and supernovae type Ia external data sets. In our extended cosmological framework, we find that a combined $\text{Planck}+\mathrm{BAO}$ analysis constrains the value of the rms density fluctuation parameter to ${\ensuremath{\sigma}}_{8}={0.781}_{\ensuremath{-}0.063}^{+0.065}$ at 95 % C.L., helping to relieve the possible tensions with the CFHTlenS cosmic shear survey. We also find a lower value for the reionization optical depth $\ensuremath{\tau}={0.058}_{\ensuremath{-}0.043}^{+0.040}$ at 95 % C.L. with respect to the one derived under the assumption of $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$. The scalar spectral index ${n}_{S}$ is now compatible with a Harrison-Zeldovich spectrum to within 2.5 standard deviations. Combining the Planck data set with the Hubble Space Telescope prior on the Hubble constant provides a value for the equation of state $w<\ensuremath{-}1$ at more than 2 standard deviations, while the neutrino effective number is fully compatible with the expectations of the standard three neutrino framework.
Institutions: Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Université Pierre-et-Marie-Curie, Sapienza University of Rome, Johns Hopkins University, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, University of Oxford, Astrophysique, Instrumentation et Modélisation, CEA Paris-Saclay
Language: Latvian
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1880593140