Wilkinson Microwave Anisotropy Probe Observations Research Articles

An Application of the Global ILC Algorithm over Large Angular Scales to Estimate the CMB Posterior Using Gibbs Sampling

Abstract In this work, we formalize a new technique to investigate the joint posterior density of the cosmic microwave background (CMB) signal and its theoretical angular power spectrum given the observed data, using the global internal-linear-combination method first proposed in a paper by Sudevan & Saha in 2017. We implement the method on low-resolution CMB maps observed by the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck satellite missions, using Gibbs sampling, assuming that the detector noise is negligible on large angular scales of the sky. The main products of our analysis are a best-fit cleaned CMB map and its theoretical angular power spectrum, along with their error estimates. We validate the method by performing Monte Carlo simulations that include realistic foreground models and noise levels consistent with WMAP and Planck observations. Our method has a unique advantage: the posterior density is obtained without any need to explicitly model foreground components. Second, the power spectrum results with the error estimates can be directly used for cosmological parameter estimations.

Results from the Wilkinson Microwave Anisotropy Probe

The Wilkinson Microwave Anisotropy Probe (WMAP) mapped the distribution of temperature and polarization over the entire sky in five microwave frequency bands. These full-sky maps were used to obtain measurements of temperature and polarization anisotropy of the cosmic microwave background with unprecedented accuracy and precision. The analysis of two-point correlation functions of temperature and polarization data gives determinations of the fundamental cosmological parameters such as the age and composition of the universe, as well as the key parameters describing the physics of inflation, which is further constrained by three-point correlation functions. WMAP observations alone reduced the flat |$\Lambda $| cold dark matter (⁠|$\Lambda $|CDM) cosmological model (six) parameter volume by a factor of |$>$|68,000 compared with pre-WMAP measurements. The WMAP observations (sometimes in combination with other astrophysical probes) convincingly show the existence of non-baryonic dark matter, the cosmic neutrino background, the flatness of the spatial geometry of the universe, a deviation from a scale-invariant spectrum of initial scalar fluctuations, and that the current universe is undergoing an accelerated expansion. The WMAP observations provide the strongest ever support for inflation; namely, the structures we see in the universe originate from quantum fluctuations generated during inflation.

Peccei-Quinn violating minimal supergravity and a 126 GeV Higgs boson

In a Peccei-Quinn extension of supergravity the $h\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ detection rate can be significantly enhanced due to the reduction of the total Higgs decay width. To assess the viability of various Peccei-Quinn extensions of minimal supergravity we perform a Bayesian analysis on three such scenarios. The main constraints on these models come from the currently observed Higgs-boson like state by the Large Hadron Collider and from the Wilkinson Microwave Anisotropy Probe observation of dark matter abundance. Our comparative study reveals that under these constraints the Peccei-Quinn violating scenarios with axino dark matter are clearly preferred over the minimal supergravity model with the lightest neutralino as a dark matter candidate.

Revisiting Cardassian model and cosmic constraint

In this paper, we revisit the Cardassian model in which the radiation energy component is included. It is important for early epoch when the radiation cannot be neglected because the equation of state (EoS) of the effective dark energy becomes time variable. Therefore, it is not equivalent to the quintessence model with a constant EoS anymore. This situation was almost overlooked in the literature. By using the recent released Union2 557 of type Ia supernovae (SN Ia), the baryon acoustic oscillation (BAO) from Sloan Digital Sky Survey and the WiggleZ data points, the full information of cosmic microwave background (CMB) measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observation, we constrain the Cardassian model via the Markov Chain Monte Carlo (MCMC) method. A tight constraint is obtained: $n= -0.0479_{- 0.0732- 0.148}^{+ 0.0730+ 0.142}$ in $1,2\sigma$ regions. The deviation of Cardassian model from quintessence model is shown in CMB anisotropic power spectra at high l's parts due to the evolution of EoS. But it is about the order of 0.1% which cannot be discriminated by current data sets. The Cardassian model is consistent with current cosmic observational data sets.

Constraint on the primordial vector mode and its magnetic field generation from seven-year Wilkinson Microwave Anisotropy Probe observations

It is often stated that the cosmological vector mode has only a decaying mode and gives negligible effects on cosmological observations. The vector mode, however, has a growing mode if there exists anisotropic stress in energy distributions in the universe. In this paper, we consider a primordial vector mode sustained by free-streaming neutrinos and its associated magnetic field generation. First, we put an observational constraint on the amount of the vector mode from the 7-year WMAP data. The constraint is found as ${r}_{v}\ensuremath{\lesssim}\ensuremath{-}\frac{r}{40}+0.012$, where ${r}_{v}$ and $r$ are the amounts of vector and tensor perturbation amplitudes with respect to the scalar one, respectively. Second, we calculate the spectrum of magnetic fields inevitably created from the primordial vector mode, given the constraint on ${r}_{v}$. It is found that the maximum amount of magnetic fields generated from the vector mode is given by $B\ensuremath{\lesssim}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{G}(\frac{{r}_{v}}{0.012}{)}^{1/2}(\frac{k}{0.002}{)}^{({n}_{v}+1)/2}$, with ${n}_{v}$ being a spectral index of the vector mode. We find a nontrivial cancellation of the magnetic field generation in the radiation-dominated era, which creates a characteristic cutoff in the magnetic field spectrum around $k\ensuremath{\approx}1.0\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$.

BAMBI: blind accelerated multimodal Bayesian inference

In this paper we present an algorithm for rapid Bayesian analysis that combines the benefits of nested sampling and artificial neural networks. The blind accelerated multimodal Bayesian inference (BAMBI) algorithm implements the MultiNest package for nested sampling as well as the training of an artificial neural network (NN) to learn the likelihood function. In the case of computationally expensive likelihoods, this allows the substitution of a much more rapid approximation in order to increase significantly the speed of the analysis. We begin by demonstrating, with a few toy examples, the ability of a NN to learn complicated likelihood surfaces. BAMBI's ability to decrease running time for Bayesian inference is then demonstrated in the context of estimating cosmological parameters from Wilkinson Microwave Anisotropy Probe and other observations. We show that valuable speed increases are achieved in addition to obtaining NNs trained on the likelihood functions for the different model and data combinations. These NNs can then be used for an even faster follow-up analysis using the same likelihood and different priors. This is a fully general algorithm that can be applied, without any pre-processing, to other problems with computationally expensive likelihood functions.

Neutrino masses and mixings in the baryon triality constrained minimal supersymmetric standard model

We discuss how the experimental neutrino oscillation data can be realized in the framework of the baryon triality (${B}_{3}$) constrained supersymmetric standard model. We show how to obtain phenomenologically viable solutions, which are compatible with the recent Wilkinson Microwave Anisotropy Probe observations. We present results for the hierarchical, inverted and degenerate cases which illustrate the possible size and structure of the lepton number violating couplings. We work with a new, as-yet unpublished version of SOFTSUSY where we implemented full one-loop neutrino masses. Finally, we shortly discuss some phenomenological implications at the LHC.

Cold dark matter isocurvature perturbations: Cosmological constraints and applications

In this paper we present the constraints on cold dark matter (CDM) isocurvature contributions to the cosmological perturbations. By employing Markov chain Monte Carlo method, we perform a global analysis for cosmological parameters using the latest astronomical data, such as 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) observations, matter power spectrum from the Sloan Digital Sky Survey, luminous red galaxies, and the Union2 type Ia supernovae sample. We find that the correlated mixture of adiabatic and isocurvature modes is slightly favored by the current observational data. We also obtain a tight limit on the fraction of the CDM isocurvature contributions, which should be less than 14.6% at 95% confidence level. With the presence of the isocurvature modes, the adiabatic spectral index becomes slightly bigger, ${n}_{s}^{\mathrm{adi}}=0.972\ifmmode\pm\else\textpm\fi{}0.014$ ($1\ensuremath{\sigma}$), and the tilt for isocurvature spectrum could be large, namely, the best fit value is ${n}_{s}^{\mathrm{iso}}=3.020$. Finally, we discuss the effect on WMAP normalization priors, shift parameter $R$, acoustic scale ${l}_{A}$, and ${z}_{*}$, from the CDM isocurvature perturbation. By fitting the mixed initial condition to the combined data, we find the mean values of $R$, ${l}_{A}$, and ${z}_{*}$ can be changed about $2.9\ensuremath{\sigma}$, $2.8\ensuremath{\sigma}$, and $1.5\ensuremath{\sigma}$ respectively, comparing with those obtained in the pure adiabatic condition.

Relic gravitational waves: Latest revisions and preparations for new data

The forthcoming release of data from the Planck mission, and possibly from the next round of Wilkinson Microwave Anisotropy Probe (WMAP) observations, make it necessary to revise the evaluations of relic gravitational waves in the existing data and, at the same time, to refine the assumptions and data analysis techniques in preparation for the arrival of new data. We reconsider with the help of the commonly used CosmoMC numerical package the previously found indications of relic gravitational waves in the 7-year (WMAP7) data. The CosmoMC approach reduces the confidence of these indications from approximately $2\ensuremath{\sigma}$ level to approximately $1\ensuremath{\sigma}$ level, but the indications do not disappear altogether. We critically analyze the assumptions that are currently used in the cosmic microwave background (CMB) data analyses, and outline the strategy that should help avoid the oversight of relic gravitational waves in the future CMB data. In particular, it is important to keep away from the unwarranted assumptions about density perturbations. The prospects of confident detection of relic gravitational waves by the Planck satellite have worsened, but they are still good. It appears that more effort will be required in order to mitigate the foreground contamination.

Cosmic constraint to DGP brane model: Geometrical and dynamical perspectives

In this paper, the Dvali-Gabadadze-Porrati (DGP) brane model is confronted by current cosmic observational data sets from geometrical and dynamical perspectives. On the geometrical side, the recently released Union2 557 of type Ia supernovae (SN Ia), the baryon acoustic oscillation from the Sloan Digital Sky Survey and the Two Degree Galaxy Redshift Survey (transverse and radial to line-of-sight data points), the cosmic microwave background measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observations [shift parameters $R$, ${l}_{a}({z}_{*})$ and redshift at the last scatter surface ${z}_{*}$], ages of high redshifts galaxies, i.e., the lookback time and the high redshift gamma ray bursts are used. On the dynamical side, data points about the growth function of matter linear perturbations are used. Using the same data set combination, we also constrain the flat $\ensuremath{\Lambda}\mathrm{CDM}$ model as a comparison. The results show that current geometrical and dynamical observational data sets much favor the flat $\ensuremath{\Lambda}\mathrm{CDM}$ model and the departure from it is above $4\ensuremath{\sigma}(6\ensuremath{\sigma})$ for the spatially flat DGP model with (without) SN systematic errors. The consistence of growth function data points is checked in terms of a relative departure of redshift-distance relation.

Comparison of dark energy models: A perspective from the latest observational data

In this paper, we compare some popular dark energy models under the assumption of a flat universe by using the latest observational data including the type Ia supernovae Constitution compilation, the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey, the cosmic microwave background measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observations and the determination of $H_0$ from the Hubble Space Telescope. Model comparison statistics such as the Bayesian and Akaike information criteria are applied to assess the worth of the models. These statistics favor models that give a good fit with fewer parameters. Based on this analysis, we find that the simplest cosmological constant model that has only one free parameter is still preferred by the current data. For other dynamical dark energy models, we find that some of them, such as the $\alpha$ dark energy, constant $w$, generalized Chaplygin gas, Chevalliear-Polarski-Linder parametrization, and holographic dark energy models, can provide good fits to the current data, and three of them, namely, the Ricci dark energy, agegraphic dark energy, and Dvali-Gabadadze-Porrati models, are clearly disfavored by the data.

Brute force reconstruction of the primordial fluctuation spectrum from five-year Wilkinson Microwave Anisotropy Probe observations

The primordial fluctuation spectrum is reconstructed from the five-year Wilkinson Microwave Anisotropy Probe data of the cosmic microwave background anisotropy. We divide the wave number space in the range of $1.23\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}\ensuremath{\lesssim}k\ensuremath{\lesssim}2.76\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$ into about 50 bins, and derive probability distributions of fluctuation amplitudes on the respective scales using Monte Carlo simulations. Although the reconstructed spectrum is basically consistent with a power-law spectrum, we find a hint of fine structure at $k\ensuremath{\approx}0.002\text{ }\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$ and $0.009\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$. The former is observed only in the temperature anisotropy, while the latter is both in the temperature and polarization anisotropies. The significance of these features are discussed, and it is shown that the deviation from a power-law spectrum at $k\ensuremath{\approx}0.009\text{ }\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$ is at $2.8\ensuremath{\sigma}$ level.

Observation number correlation inWMAPdata

A remarkable similarity between the large-scale non-Gaussian pattern of cosmic microwave background (CMB) temperatures obtained by Wilkinson Microwave Anisotropy Probe (WMAP) mission and the distribution feature of observation numbers is noted. Motivated from such a similarity, in this work we check the WMAP data for the correlation between pixel temperature t and observation number N. Systematic effect of imbalance differential observation and significant t-N correlation in magnitude, distribution non-Gaussianity and north-south asymmetry are found. Our results indicate that, for precision cosmology study based on WMAP observations, the observation effect on released WMAP temperature maps has to be further carefully studied.

Holographic Ricci dark energy: Current observational constraints, quintom feature, and the reconstruction of scalar-field dark energy

In this work, we consider the cosmological constraints on the holographic Ricci dark energy proposed by Gao et al. [Phys. Rev. D 79, 043511 (2009)], by using the observational data currently available. The main characteristic of holographic Ricci dark energy is governed by a positive numerical parameter $\ensuremath{\alpha}$ in the model. When $\ensuremath{\alpha}l1/2$, the holographic Ricci dark energy will exhibit a quintomlike behavior; i.e., its equation of state will evolve across the cosmological-constant boundary $w=\ensuremath{-}1$. The parameter $\ensuremath{\alpha}$ can be determined only by observations. Thus, in order to characterize the evolving feature of dark energy and to predict the fate of the Universe, it is of extraordinary importance to constrain the parameter $\ensuremath{\alpha}$ by using the observational data. In this paper, we derive constraints on the holographic Ricci dark energy model from the latest observational data including the Union sample of 307 type Ia supernovae, the shift parameter of the cosmic microwave background given by the five-year Wilkinson Microwave Anisotropy Probe observations, and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey. The joint analysis gives the best-fit results (with $1\ensuremath{\sigma}$ uncertainty): $\ensuremath{\alpha}={0.359}_{\ensuremath{-}0.025}^{+0.024}$ and ${\ensuremath{\Omega}}_{\mathrm{m}0}={0.318}_{\ensuremath{-}0.024}^{+0.026}$. That is to say, according to the observations, the holographic Ricci dark energy takes on the quintom feature. Finally, in light of the results of the cosmological constraints, we discuss the issue of the scalar-field dark energy reconstruction, based on the scenario of the holographic Ricci vacuum energy.

Relic density in nonuniversal gaugino mass models with SO(10) GUT symmetry

Nonuniversal boundary conditions in grand unified theories can lead to nonuniversal gaugino masses at the unification scale. In $R$-parity preserving theories the lightest supersymmetric particle is a natural candidate for the dark matter. The composition of the lightest neutralino and the identity of the next-to-lightest supersymmetric particle are studied, when nonuniversal gaugino masses come from representations of SO(10). In these cases, the thermal relic density compatible with the Wilkinson Microwave Anisotropy Probe observations is found. Relic densities are compared with the universal case. Mass spectra in the studied cases are discussed.

The variation of the electromagnetic coupling and quintessence

The properties of quintessence are examined through the study of the variation of the electromagnetic coupling. We consider two simple quintessence models with a modified exponential potential and study the parameter space constraints derived from the existing observational bounds on the variation of the fine structure constant and the most recent Wilkinson Microwave Anisotropy Probe observations.

FIVE-YEARWILKINSON MICROWAVE ANISOTROPY PROBEOBSERVATIONS: LIKELIHOODS AND PARAMETERS FROM THEWMAPDATA

The Wilkinson Microwave Anisotropy Probe (WMAP), launched in 2001, has mapped out the Cosmic Microwave Background with unprecedented accuracy over the whole sky. Its observations have led to the establishment of a simple concordance cosmological model for the contents and evolution of the universe, consistent with virtually all other astronomical measurements. The WMAP first-year and three-year data have allowed us to place strong constraints on the parameters describing the ACDM model. a flat universe filled with baryons, cold dark matter, neutrinos. and a cosmological constant. with initial fluctuations described by nearly scale-invariant power law fluctuations, as well as placing limits on extensions to this simple model (Spergel et al. 2003. 2007). With all-sky measurements of the polarization anisotropy (Kogut et al. 2003; Page et al. 2007), two orders of magnitude smaller than the intensity fluctuations. WMAP has not only given us an additional picture of the universe as it transitioned from ionized to neutral at redshift z approx.1100. but also an observation of the later reionization of the universe by the first stars. In this paper we present cosmological constraints from WMAP alone. for both the ACDM model and a set of possible extensions. We also consider tlle consistency of WMAP constraints with other recent astronomical observations. This is one of seven five-year WMAP papers. Hinshaw et al. (2008) describe the data processing and basic results. Hill et al. (2008) present new beam models arid window functions, Gold et al. (2008) describe the emission from Galactic foregrounds, and Wright et al. (2008) the emission from extra-Galactic point sources. The angular power spectra are described in Nolta et al. (2008), and Komatsu et al. (2008) present and interpret cosmological constraints based on combining WMAP with other data. WMAP observations are used to produce full-sky maps of the CMB in five frequency bands centered at 23, 33, 41, 61, and 94 GHz (Hinshaw et al. 2008). With five years of data, we are now able to place better limits on the ACDM model. as well as to move beyond it to test the composition of the universe. details of reionization. sub-dominant components, characteristics of inflation, and primordial fluctuations. We have more than doubled the amount of polarized data used for cosmological analysis. allowing a better measure of the large-scale E-mode signal (Nolta et al. 2008). To this end we describe an alternative way to remove Galactic foregrounds from low resolution polarization maps in which Galactic emission is marginalized over, providing a cross-check of our results. With longer integration we also better probe the second and third acoustic peaks in the temperature angular power spectrum, and have many more year-to-year difference maps available for cross-checking systematic effects (Hinshaw et al. 2008).

On the road to discovery of relic gravitational waves: TheTEandBBcorrelations in the cosmic microwave background radiation

The detection of primordial gravitational waves is one of the biggest challenges of the present time. The existing (Wilkinson Microwave Anisotropy Probe) observations are helpful in achieving this goal, and the forthcoming experiments (Planck) are likely to complete this mission. We show that the 5-year Wilkinson Microwave Anisotropy Probe $TE$ data contain a hint of the presence of the gravitational wave contribution. In terms of the parameter $R$, which gives the ratio of contributions from gravitational waves and density perturbations to the temperature quadrupole, the best-fit model produced $R=0.24$. Because of large residual noises, the uncertainty of this determination is still large, and it easily includes the $R=0$ hypothesis. However, the uncertainty will be strongly reduced in the forthcoming observations which are more sensitive. We numerically simulated the Planck data and concluded that the relic gravitational waves with $R=0.24$ will be present at a better than $3\ensuremath{\sigma}$ level in the $TE$ observational channel, and at a better than $2\ensuremath{\sigma}$ level in the ``realistic'' $BB$ channel. The balloon-borne and ground-based observations may provide healthy competition for Planck in some parts of the lower-$\ensuremath{\ell}$ spectrum.

A Novel Method for Measuring the Extragalactic Background Light: Fermi Application to the Lobes of Fornax A

We describe a new method for measuring the extragalactic background light (EBL) through the detection of γ-ray inverse Compton (IC) emission due to scattering of the EBL photons off relativistic electrons in the lobes of radio galaxies. Our method has no free physical parameters and is a powerful tool when the lobes are characterized by a high-energy sharp break or cutoff in their electron energy distribution (EED). We show that such a feature will produce a high-energy IC imprint of the EBL spectrum in which the radio lobes are embedded and show how this imprint can be used to derive the EBL. We apply our method to the bright nearby radio galaxy Fornax A, for which we demonstrate, using Wilkinson Microwave Anisotropy Probe (WMAP) and EGRET observations, that the EED of its lobes is characterized by a conveniently located cutoff, bringing the IC EBL emission into the Fermi Gamma-Ray Space Telescope energy range. We show that Fermi will set upper limits to the optical EBL and measure the more elusive infrared EBL.

Looking for the Sunyaev-Zel'dovich effect in the Virgo cluster from WMAP and ROSAT data

Wilkinson Microwave Anisotropy Probe (WMAP) observations at millimetre wavelengths are sensitive to the Sunyaev–Zel’dovich (SZ) effect in galaxy clusters. Among all the objects in the sky, the Virgo cluster is expected to provide the largest integrated signal. Based on models compatible with the X-ray emission observed in the ROSAT All-Sky Survey, we predict an approximately 2σ detection of the SZ effect from Virgo in the WMAP 3-yr data. Our analysis reveals a 3σ signal on scales of 5 ◦ , although the frequency dependence deviates from the theoretical expectation for the SZ effect. The main sources of uncertainty are instrumental noise, and, most importantly, possible contamination from point sources and diffuse back/foregrounds. In particular, a population of unresolved extragalactic sources in Virgo would explain the observed intensity and frequency dependence. In order to resolve this question, one needs to wait for experiments like Planck to achieve the required accuracy.