370 research outputs found
Planck 2013 results. XXII. Constraints on inflation
We analyse the implications of the Planck data for cosmic inflation. The Planck nominal mission temperature anisotropy measurements, combined with the WMAP large-angle polarization, constrain the scalar spectral index to be ns = 0:9603 _ 0:0073, ruling out exact scale invariance at over 5_: Planck establishes an upper bound on the tensor-to-scalar ratio of r < 0:11 (95% CL). The Planck data thus shrink the space of allowed standard inflationary models, preferring potentials with V00 < 0. Exponential potential models, the simplest hybrid inflationary models, and monomial potential models of degree n _ 2 do not provide a good fit to the data. Planck does not find statistically significant running of the scalar spectral index, obtaining dns=dln k = 0:0134 _ 0:0090. We verify these conclusions through a numerical analysis, which makes no slowroll approximation, and carry out a Bayesian parameter estimation and model-selection analysis for a number of inflationary models including monomial, natural, and hilltop potentials. For each model, we present the Planck constraints on the parameters of the potential and explore several possibilities for the post-inflationary entropy generation epoch, thus obtaining nontrivial data-driven constraints. We also present a direct reconstruction of the observable range of the inflaton potential. Unless a quartic term is allowed in the potential, we find results consistent with second-order slow-roll predictions. We also investigate whether the primordial power spectrum contains any features. We find that models with a parameterized oscillatory feature improve the fit by __2 e_ _ 10; however, Bayesian evidence does not prefer these models. We constrain several single-field inflation models with generalized Lagrangians by combining power spectrum data with Planck bounds on fNL. Planck constrains with unprecedented accuracy the amplitude and possible correlation (with the adiabatic mode) of non-decaying isocurvature fluctuations. The fractional primordial contributions of cold dark matter (CDM) isocurvature modes of the types expected in the curvaton and axion scenarios have upper bounds of 0.25% and 3.9% (95% CL), respectively. In models with arbitrarily correlated CDM or neutrino isocurvature modes, an anticorrelated isocurvature component can improve the _2 e_ by approximately 4 as a result of slightly lowering the theoretical prediction for the ` <_ 40 multipoles relative to the higher multipoles. Nonetheless, the data are consistent with adiabatic initial conditions
Planck intermediate results L : Evidence of spatial variation of the polarized thermal dust spectral energy distribution and implications for CMB B-mode analysis
The characterization of the Galactic foregrounds has been shown to be the main obstacle in the challenging quest to detect primordial B-modes in the polarized microwave sky. We make use of the Planck-HFI 2015 data release at high frequencies to place new constraints on the properties of the polarized thermal dust emission at high Galactic latitudes. Here, we specifically study the spatial variability of the dust polarized spectral energy distribution (SED), and its potential impact on the determination of the tensor-to-scalar ratio, r. We use the correlation ratio of the CBB `angular power spectra between the 217 and 353 GHz channels as a tracer of these potential variations, computed on different high Galactic latitude regions, ranging from 80% to 20% of the sky. The new insight from Planck data is a departure of the correlation ratio from unity that cannot be attributed to a spurious decorrelation due to the cosmic microwave background, instrumental noise, or instrumental systematics. The effect is marginally detected on each region, but the statistical combination of all the regions gives more than 99% confidence for this variation in polarized dust properties. In addition, we show that the decorrelation increases when there is a decrease in the mean column density of the region of the sky being considered, and we propose a simple power-law empirical model for this dependence, which matches what is seen in the Planck data. We explore the effect that this measured decorrelation has on simulations of the BICEP2-Keck Array/Planck analysis and show that the 2015 constraints from these data still allow a decorrelation between the dust at 150 and 353 GHz that is compatible with our measured value. Finally, using simplified models, we show that either spatial variation of the dust SED or of the dust polarization angle are able to produce decorrelations between 217 and 353 GHz data similar to the values we observe in the data.Peer reviewe
VisibilitĂ© et prĂ©sence de lâimage dans lâespace ecclĂ©sial
Cet ouvrage met au cĆur de son propos une interrogation simple : dans lâorganisation complexe de lâespace de lâĂ©glise mĂ©diĂ©vale, les emplacements choisis pour les images qui ornent les murs et les objets nâoffrent pas toujours la possibilitĂ© de voir celles-ci, dâen dĂ©chiffrer le contenu. Certaines semblent rĂ©servĂ©es Ă des groupes de lâassemblĂ©e stationnant dans des espaces spĂ©cifiques, dâautres ne sont pas visibles depuis les principales zones affectĂ©es aux fidĂšles ou aux clercs, dâautres encore sont situĂ©es trop haut. Le rapport, a priori Ă©vident, entre reprĂ©sentation et visibilitĂ© se trouve donc souvent dĂ©menti, appelant alors une nouvelle notion, celle de prĂ©sence. Analyser la tension existant entre ces trois catĂ©gories â figuration, visibilitĂ© et prĂ©sence â implique une Ă©tude croisĂ©e des Ćuvres figurĂ©es, des monuments et des sources Ă©crites. Les notions de mobilitĂ© et de fixitĂ© permettent Ă©galement de prendre en compte les multiples jeux dâĂ©chelles Ă lâĆuvre dans ce lieu rituel quâest lâĂ©glise, impliquant des objets, des manuscrits, des dispositifs liturgiques, des gestes, des dĂ©placements physiques, dialoguant avec un dĂ©cor appliquĂ© au corps mĂȘme du monument, Ă©pousant lâimmobilitĂ© de lâarchitecture. Les cinq chapitres thĂ©matiques qui organisent ce volume mettent en regard diffĂ©rents cas issus de lâOccident mĂ©diĂ©val et de lâOrient byzantin, selon une chronologie longue (de lâAntiquitĂ© tardive Ă la fin du Moyen Ăge), dans une volontĂ© de dĂ©cloisonner les disciplines et les aires gĂ©ographiques afin de tirer tous les enseignements dâune approche transversale de lâimage mĂ©diĂ©vale
Planck intermediate results. L. Evidence of spatial variation of the polarized thermal dust spectral energy distribution and implications for CMB B-mode analysis
The characterization of the Galactic foregrounds has been shown to be the main obstacle in thechallenging quest to detect primordial B-modes in the polarized microwave sky. We make use of the Planck-HFI 2015 data release at high frequencies to place new constraints on the properties of the polarized thermal dust emission at high Galactic latitudes. Here, we specifically study the spatial variability of the dust polarized spectral energy distribution (SED), and its potential impact on the determination of the tensor-to-scalar ratio, r. We use the correlation ratio of the CBBâ angular power spectra between the 217 and 353âGHz channels as a tracer of these potential variations, computed on different high Galactic latitude regions, ranging from 80% to 20% of the sky. The new insight from Planck data is a departure of the correlation ratio from unity that cannot be attributed to a spurious decorrelation due to the cosmic microwave background, instrumental noise, or instrumental systematics. The effect is marginally detected on each region, but the statistical combination of all the regions gives more than 99% confidence for this variation in polarized dust properties. In addition, we show that the decorrelation increases when there is a decrease in the mean column density of the region of the sky being considered, and we propose a simple power-law empirical model for this dependence, which matches what is seen in the Planck data. We explore the effect that this measured decorrelation has on simulations of the BICEP2-Keck Array/Planck analysis and show that the 2015 constraints from these data still allow a decorrelation between the dust at 150 and 353âGHz that is compatible with our measured value. Finally, using simplified models, we show that either spatial variation of the dust SED or of the dust polarization angle are able to produce decorrelations between 217 and 353âGHz data similar to the values we observe in the data
Planck Early Results XXVI: Detection with Planck and confirmation by XMM-Newton of PLCK G266.6-27.3, an exceptionally X-ray luminous and massive galaxy cluster at z~1
We present first results on PLCK G266.6-27.3, a galaxy cluster candidate
detected at a signal-to-noise ratio of 5 in the Planck All Sky survey. An
XMM-Newton validation observation has allowed us to confirm that the candidate
is a bona fide galaxy cluster. With these X-ray data we measure an accurate
redshift, z = 0.94 +/- 0.02, and estimate the cluster mass to be M_500 = (7.8
+/- 0.8)e+14 solar masses. PLCK G266.6-27.3 is an exceptional system: its
luminosity of L_X(0.5-2.0 keV)=(1.4 +/- 0.05)e+45 erg/s, equals that of the two
most luminous known clusters in the z > 0.5 universe, and it is one of the most
massive clusters at z~1. Moreover, unlike the majority of high-redshift
clusters, PLCK G266.6-27.3 appears to be highly relaxed. This observation
confirms Planck's capability of detecting high-redshift, high-mass clusters,
and opens the way to the systematic study of population evolution in the
exponential tail of the mass function.Comment: 6 pages, 3 figures; final version accepted for publication in A&A ;
minor changes in Sec.2.,3.2 and 4.1; Table 1: misprint on R500 error
corrected; abundance value adde
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