High‐Resolution Simulations of Non‐Gaussian Cosmic Microwave Background Maps in Spherical Coordinates

Liguori, M.; Matarrese, S.; Moscardini, L.

doi:10.1086/378394

Cited by 64 publications

(113 citation statements)

References 45 publications

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“…A different method has then been proposed in Liguori et al (2003Liguori et al ( , 2007, where the authors work with filter functions to introduce the proper spatial correlations of the primordial potential. The current version of the model uses maps generated according to the method of Elsner & Wandelt (2009), a recent improvement of the method of Liguori et al (2003) with better numerical efficiency.…”

Section: Non-gaussian Cmb Anisotropiesmentioning

confidence: 99%

The pre-launchPlanckSky Model: a model of sky emission at submillimetre to centimetre wavelengths

Delabrouille

Betoule

Melin

et al. 2013

A&A

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We present the Planck Sky Model (PSM), a parametric model for generating all-sky, few arcminute resolution maps of sky emission at submillimetre to centimetre wavelengths, in both intensity and polarisation. Several options are implemented to model the cosmic microwave background, Galactic diffuse emission (synchrotron, free-free, thermal and spinning dust, CO lines), Galactic H ii regions, extragalactic radio sources, dusty galaxies, and thermal and kinetic Sunyaev-Zeldovich signals from clusters of galaxies. Each component is simulated by means of educated interpolations/extrapolations of data sets available at the time of the launch of the Planck mission, complemented by state-of-the-art models of the emission. Distinctive features of the simulations are spatially varying spectral properties of synchrotron and dust; different spectral parameters for each point source; modelling of the clustering properties of extragalactic sources and of the power spectrum of fluctuations in the cosmic infrared background. The PSM enables the production of random realisations of the sky emission, constrained to match observational data within their uncertainties. It is implemented in a software package that is regularly updated with incoming information from observations. The model is expected to serve as a useful tool for optimising planned microwave and sub-millimetre surveys and testing data processing and analysis pipelines. It is, in particular, used to develop and validate data analysis pipelines within the Planck collaboration. A version of the software that can be used for simulating the observations for a variety of experiments is made available on a dedicated website.

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Section: Non-gaussian Cmb Anisotropiesmentioning

confidence: 99%

The pre-launchPlanckSky Model: a model of sky emission at submillimetre to centimetre wavelengths

Delabrouille

Betoule

Melin

et al. 2013

A&A

Self Cite

208

232

View full text Add to dashboard Cite

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“…The generation of non-Gaussian CMB maps for a more realistic CMB sky has been described in [87,88]. Following [88], we can write the temperature multipole moments as an integration over multipole moments of the Bardeen potential as a function of comoving distance r:…”

Section: Appendix D: Notes On Numerical Realizationsmentioning

confidence: 99%

Large-scale anomalies in the cosmic microwave background as signatures of non-Gaussianity

2016

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We derive a general expression for the probability of observing deviations from statistical isotropy in the cosmic microwave background (CMB) if the primordial fluctuations are non-Gaussian and extend to superhorizon scales. The primary motivation is to properly characterize the monopole and dipole modulations of the primordial power spectrum that are generated by the coupling between superhorizon and subhorizon perturbations. Unlike previous proposals for generating the hemispherical power asymmetry, we do not assume that the power asymmetry results from a single large superhorizon mode. Instead, we extrapolate the observed power spectrum to superhorizon scales and compute the power asymmetry that would result from a specific realization of non-Gaussian perturbations on scales larger than the observable universe. Our study encompasses many of the scenarios that have been put forward as possible explanations for the CMB hemispherical power asymmetry. We confirm our analytic predictions for the probability of a given power asymmetry by comparing them to numerical realizations of CMB maps. We find that non-local models of nonGaussianity and scale-dependent local non-Gaussianity produce scale-dependent modulations of the power spectrum, thereby potentially producing both a monopolar and a dipolar power modulation on large scales. We then provide simple examples of finding the posterior distributions for the parameters of the bispectrum from the observed monopole and dipole modulations.

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“…However, while those simulations make use of several approximation schemes in order to produce numerically viable codes, our expressions are exact and analytical. In particular, our results show that the transfer functions of [29,30] have an invariant (or geometrical) piece which is described by our spacetime window functions, so that the transfer functions can be obtained by integration of these window functions over time with some visibility function. Another work close in spirit to ours was done by Bashinsky and Bertshinger [34,35], who calculated the Green's function for the evolution of linear cosmological perturbations in position space but did not compute the Green's functions for the anisotropies.…”

Section: Introductionmentioning

confidence: 74%

CMB in a box: Causal structure and the Fourier-Bessel expansion

2010

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This paper makes two points. First, we show that the line-of-sight solution to cosmic microwave anisotropies in Fourier space, even though formally defined for arbitrarily large wavelengths, leads to position-space solutions which only depend on the sources of anisotropies inside the past lightcone of the observer. This foretold manifestation of causality in position (real) space happens order by order in a series expansion in powers of the visibility γ = e −µ , where µ is the optical depth to Thompson scattering. We show that the contributions of order γ N to the CMB anisotropies are regulated by spacetime window functions which have support only inside the past light-cone of the point of observation. Second, we show that the Fourier-Bessel expansion of the physical fields (including the temperature and polarization momenta) is an alternative to the usual Fourier basis as a framework to compute the anisotropies. The viability of the Fourier-Bessel series for treating the CMB is a consequence of the fact that the visibility function becomes exponentially small at redshifts z 10 3 , effectively cutting off the past light-cone and introducing a finite radius inside which initial conditions can affect physical observables measured at our position x = 0 and time t0. Hence, for each multipole there is a discrete tower of momenta k i (not a continuum) which can affect physical observables, with the smallest momenta being k 1 ∼ . The Fourier-Bessel modes take into account precisely the information from the sources of anisotropies that propagates from the initial value surface to the point of observation -no more, no less. We also show that the physical observables (the temperature and polarization maps), and hence the angular power spectra, are unaffected by that choice of basis. This implies that the Fourier-Bessel expansion is the optimal scheme with which one can compute CMB anisotropies.

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High‐Resolution Simulations of Non‐Gaussian Cosmic Microwave Background Maps in Spherical Coordinates

Cited by 64 publications

References 45 publications

The pre-launchPlanckSky Model: a model of sky emission at submillimetre to centimetre wavelengths

The pre-launchPlanckSky Model: a model of sky emission at submillimetre to centimetre wavelengths

Large-scale anomalies in the cosmic microwave background as signatures of non-Gaussianity

CMB in a box: Causal structure and the Fourier-Bessel expansion

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