* Astronomy

Blobrana · L

RE: Planck satellite

Blobrana · L

Title: Planck Planck 2013 results. XXIII. Isotropy and Statistics of the CMB
Authors: Planck Collaboration: P. A. R. Ade, N. Aghanim, C. Armitage-Caplan, M. Arnaud, M. Ashdown, F. Atrio-Barandela, J. Aumont, C. Baccigalupi, A. J. Banday, R. B. Barreiro, J. G. Bartlett, N. Bartolo, E. Battaner, R. Battye, K. Benabed, A. Benoît, A. Benoit-Lévy, J.-P. Bernard, M. Bersanelli, P. Bielewicz, J. Bobin, J. J. Bock, A. Bonaldi, L. Bonavera, J. R. Bond, J. Borrill, F. R. Bouchet, M. Bridges, M. Bucher, C. Burigana, R. C. Butler, J.-F. Cardoso, A. Catalano, A. Challinor, A. Chamballu, R.-R. Chary, L.-Y Chiang, H. C. Chiang, P. R. Christensen, S. Church, D. L. Clements, S. Colombi, L. P. L. Colombo, F. Couchot, A. Coulais, B. P. Crill, M. Cruz, A. Curto, F. Cuttaia, L. Danese, R. D. Davies, R. J. Davis, P. de Bernardis, A. de Rosa, G. de Zotti, J. Delabrouille, J.-M. Delouis, et al. (193 additional authors not shown)

The two fundamental assumptions of the standard cosmological model - that the initial fluctuations are statistically isotropic and Gaussian - are rigorously tested using maps of the CMB anisotropy from the \Planck\ satellite. The detailed results are based on studies of four independent estimates of the CMB that are compared to simulations using a fiducial \Lambda CDM model and incorporating essential aspects of the Planck measurement process. Deviations from isotropy have been found and demonstrated to be robust against component separation algorithm, mask and frequency dependence. Many of these anomalies were previously observed in the WMAP data, and are now confirmed at similar levels of significance (around 3\sigma). However, we find little evidence for non-Gaussianity with the exception of a few statistical signatures that seem to be associated with specific anomalies. In particular, we find that the quadrupole-octopole alignment is also connected to a low observed variance of the CMB signal. The dipolar power asymmetry is now found to persist to much smaller angular scales, and can be described in the low-\ell regime by a phenomenological dipole modulation model. Finally, it is plausible that some of these features may be reflected in the angular power spectrum of the data which shows a deficit of power on the same scales. Indeed, when the power spectra of two hemispheres defined by a preferred direction are considered separately, one shows evidence for a deficit in power, whilst its opposite contains oscillations between odd and even modes that may be related to the parity violation and phase correlations also detected in the data. Whilst these analyses represent a step forward in building an understanding of the anomalies, a satisfactory explanation based on physically motivated models is still lacking.

Read more (7552kb, PDF)

Blobrana · L

Title: Planck 2013 results. XXII. Constraints on inflation
Authors: Planck Collaboration: P. A. R. Ade, N. Aghanim, C. Armitage-Caplan, M. Arnaud, M. Ashdown, F. Atrio-Barandela, J. Aumont, C. Baccigalupi, A. J. Banday, R. B. Barreiro, J. G. Bartlett, N. Bartolo, E. Battaner, K. Benabed, A. Benoit, A. Benoit-Levy, J.-P. Bernard, M. Bersanelli, P. Bielewicz, J. Bobin, J. J. Bock, A. Bonaldi, J. R. Bond, J. Borrill, F. R. Bouchet, M. Bridges, M. Bucher, C. Burigana, R. C. Butler, E. Calabrese, J.-F. Cardoso, A. Catalano, A. Challinor, A. Chamballu, L.-Y Chiang, H. C. Chiang, P. R. Christensen, S. Church, D. L. Clements, S. Colombi, L. P. L. Colombo, F. Couchot, A. Coulais, B. P. Crill, A. Curto, F. Cuttaia, L. Danese, R. D. Davies, R. J. Davis, P. de Bernardis, A. de Rosa, G. de Zotti, J. Delabrouille, J.-M. Delouis, F.-X. Desert, C. Dickinson, J. M. Diego, et al. (181 additional authors not shown)

We analyse the implications of the Planck data for cosmic inflation. The Planck nominal mission temperature anisotropy measurements, combined with the WMAP large-angle polarisation, constrain the scalar spectral index to n_s = 0.960 ± 0.0073, ruling out exact scale invariance at over 5 sigma. Planck establishes an upper bound on the tensor-to-scalar ratio at r < 0.11 (95% CL). Planck data shrink the space of allowed standard inflationary models, preferring potentials with V'' < 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 any statistically significant running of the scalar spectral index, obtaining d n_s/d ln k = -0.0134 ± 0.0090. Several analyses dropping the slow-roll approximation are carried out, including detailed model comparison and inflationary potential reconstruction. We investigate whether the primordial power spectrum contains any features. A penalised likelihood approach suggests a feature near the smallest scales probed by Planck at an estimated significance of ~3 sigma after correction for the look elsewhere effect. Models with a parameterised oscillatory feature can improve the fit chi² by ~ 10; however, Bayesian evidence does not prefer these models. We constrain several single-field inflation models with generalised Lagrangians by combining power spectrum data with bounds on f_NL measured by Planck. The fractional primordial contribution of CDM isocurvature modes in the curvaton and axion scenarios has upper bounds of 0.25% or 3.9% (95% CL), respectively. In models with arbitrarily correlated CDM or neutrino isocurvature modes, an anticorrelation can improve chi² by ~4 due to a moderate tension between l < 40 and higher multipoles. Nonetheless, the data are consistent with adiabatic initial conditions.

Read more (8372kb, PDF)

Blobrana · L

Title: Implications of Planck results for models with local type non-Gaussianity
Authors: Teruaki Suyama, Tomo Takahashi, Masahide Yamaguchi, Shuichiro Yokoyama

We discuss implications of Planck results for models with local type non-Gaussianity. In light of the recent results of the Planck satellite, we constrain model parameters of several representative models and give the prediction of trispectrum, in particular, gNL. We also consider interesting possibilities that trispectrum appears as the first signature of the non-Gaussianities of the curvature perturbations, that is, fNL is small while gNL can be significantly large.

Read more (16kb, PDF)

Blobrana · L

Title: Planck 2013 results. XXVI. Background geometry and topology of the Universe
Authors: Planck Collaboration: P. A. R. Ade, N. Aghanim, C. Armitage-Caplan, M. Arnaud, M. Ashdown, F. Atrio-Barandela, J. Aumont, C. Baccigalupi, A. J. Banday, R. B. Barreiro, J. G. Bartlett, E. Battaner, K. Benabed, A. Benoît, A. Benoit-Lévy, J.-P. Bernard, M. Bersanelli, P. Bielewicz, J. Bobin, J. J. Bock, A. Bonaldi, L. Bonavera, J. R. Bond, J. Borrill, F. R. Bouchet, M. Bridges, M. Bucher, C. Burigana, R. C. Butler, J.-F. Cardoso, A. Catalano, A. Challinor, A. Chamballu, L.-Y Chiang, H. C. Chiang, P. R. Christensen, S. Church, D. L. Clements, S. Colombi, L. P. L. Colombo, F. Couchot, A. Coulais, B. P. Crill, A. Curto, F. Cuttaia, L. Danese, R. D. Davies, R. J. Davis, P. de Bernardis, A. de Rosa, G. de Zotti, J. Delabrouille, J.-M. Delouis, F.-X. Désert, J. M. Diego, H. Dole, S. Donzelli, et al. (168 additional authors not shown)

Planck CMB temperature maps allow us to detect departures from homogeneity and isotropy on the largest scales. We search for topology with a fundamental domain (nearly) intersecting the last scattering surface (comoving distance X_r). For most topologies studied the likelihood maximised over the orientation relative to the observed map shows some preference for multi-connected models just larger than X_r. Since this effect is also present in simulated realisations of isotropic maps, we interpret it as the inevitable alignment of mild anisotropic correlations with chance features in a single sky realisation; such a feature can also be present, in milder form, when the likelihood is marginalised over orientations. Thus marginalised, the limits on the radius R_i of the largest sphere inscribed in a topological domain (at log-likelihood-ratio -5) are: in a flat Universe, R_i>0.9X_r for the cubic torus (cf. R_i>0.9X_r at 99% CL for the matched-circles search); R_i>0.7X_r for the chimney; R_i>0.5X_r for the slab; in a positively curved Universe, R_i>1.0X_r for the dodecahedron; R_i>1.0X_r for the truncated cube; and R_i>0.9X_r for the octahedron.
We perform a Bayesian search for an anisotropic Bianchi VII_h geometry. In a non-physical setting where the Bianchi parameters are decoupled from the standard cosmology, Planck data favour a Bianchi component with a Bayes factor of at least 1.5 units of log-evidence. Indeed, a Bianchi pattern is quite efficient at accounting for some large-scale anomalies seen in Planck data. However, the cosmological parameters are in strong disagreement with those found from CMB anisotropy data alone. In the physically motivated setting where the Bianchi parameters are fitted simultaneously with the standard cosmological parameters, we find no evidence for a Bianchi VII_h cosmology and constrain the vorticity of such models at (w/H)_0<8e-10 (95% CL).

Read more (3976kb, PDF)

Blobrana · L

Title: Planck 2013 results. I. Overview of products and scientific results
Authors: Planck Collaboration: P. A. R. Ade, N. Aghanim, C. Armitage-Caplan, M. Arnaud, M. Ashdown, F. Atrio-Barandela, J. Aumont, C. Baccigalupi, A. J. Banday, R. B. Barreiro, M. Bartelmann, J. G. Bartlett, E. Battaner, K. Benabed, A. Benoît, A. Benoit-Lévy, J.-P. Bernard, M. Bersanelli, P. Bielewicz, J. Bobin, J. J. Bock, A. Bonaldi, J. R. Bond, J. Borrill, F. R. Bouchet, F. Boulanger, J. W. Bowyer, M. Bridges, M. Bucher, C. Burigana, R. C. Butler, B. Cappellini, J.-F. Cardoso, R. Carr, M. Casale, A. Catalano, A. Challinor, A. Chamballu, R.-R. Chary, X. Chen, L.-Y Chiang, H. C. Chiang, P. R. Christensen, S. Church, D. L. Clements, S. Colombi, L. P. L. Colombo, F. Couchot, A. Coulais, B. P. Crill, A. Curto, F. Cuttaia, L. Danese, R. D. Davies, R. J. Davis, P. de Bernardis, A. de Rosa, G. de Zotti, et al. (218 additional authors not shown)

The ESA's Planck satellite, dedicated to studying the early universe, was launched on May 2009 and has been surveying the microwave and submillimetre sky since August 2009. In March 2013, ESA and the Planck Collaboration publicly released the initial cosmology products based on the first 15.5 months of Planck operations, along with a set of scientific and technical papers and a web-based explanatory supplement. This paper describes the mission and its performance, and gives an overview of the processing and analysis of the data, the characteristics of the data, the main scientific results, and the science data products and papers in the release. Scientific results include robust support for the standard, six parameter LCDM model of cosmology and improved measurements for the parameters that define this model, including a highly significant deviation from scale invariance of the primordial power spectrum. The Planck values for some of these parameters and others derived from them are significantly different from those previously determined. Several large scale anomalies in the CMB temperature distribution detected earlier by WMAP are confirmed with higher confidence. Planck sets new limits on the number and mass of neutrinos, and has measured gravitational lensing of CMB anisotropies at 25 sigma. Planck finds no evidence for non-Gaussian statistics of the CMB anisotropies. There is some tension between Planck and WMAP results; this is evident in the power spectrum and results for some of the cosmology parameters. In general, Planck results agree well with results from the measurements of baryon acoustic oscillations. Because the analysis of Planck polarisation data is not yet as mature as the analysis of temperature data, polarization results are not released. We do, however, illustrate the robust detection of the E-mode polarisation signal around CMB hot- and cold-spots.

Read more (7135kb, PDF)

Blobrana · L

Planck Satellite reveals an almost perfect Universe

Acquired by ESA's Planck space telescope, the most detailed map ever created of the cosmic microwave background - the relic radiation from the Big Bang - was released today revealing the existence of features that challenge the foundations of our current understanding of the Universe.
The image is based on the initial 15.5 months of data from Planck and is the mission's first all-sky picture of the oldest light in our Universe, imprinted on the sky when it was just 380 000 years old.
Read more

Blobrana · L

This Thursday, scientists will unveil the best image yet of the cosmic microwave background - the 'afterglow' of the Big Bang - by ESA's Planck space telescope.
The new map will be presented and discussed at a dedicated press conference held at ESA Headquarters on Thursday at 10:00 CET. The event will be streamed live via www.esa.int
Read more

Blobrana · L

NASA TV News Conference to Discuss Planck Cosmology Findings

NASA will host a news conference at 15:00 UT, Thursday, March 21, to discuss the first cosmology results from Planck, a European Space Agency mission with significant NASA participation.
Read more

Blobrana · L

Call for Media: First cosmology results from ESA's Planck mission

Media representatives are invited to a briefing on the first cosmology data release from ESA's Planck mission. The new results include Planck's first all-sky map of the cosmic microwave background.
The media briefing is being organised by the European Space Agency at Headquarters, 8-10 rue Mario Nikis in Paris, on 21 March 2013, 10:00-12:00 CET. Doors open at 09:30 CET.
There will be an additional session in the afternoon, 14:00-15:45 CET, for the scientific community and science journalists.
Read more