Gravitational lensing of the cosmic microwave background by non-linear structures

Merkel, Philipp M.; Schäfer, Björn Malte

doi:10.1111/j.1365-2966.2010.17739.x

Cited by 9 publications

(20 citation statements)

References 28 publications

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“…The code and its forthcoming version will be publicly available. the subpercent level (Merkel & Schäfer 2011).The assumption of a purely Gaussian lensing potential is thus well applicable and usually sufficient for this kind of simulations. As an alternative, the code can accept pre-computed maps of the potential on the input, which can be therefore arbitrarily non-Gaussian, and which will be used to produce the displacement field.…”

Section: Discussionmentioning

confidence: 99%

High-precision simulations of the weak lensing effect on cosmic microwave background polarization

Fabbian

Stompor

2013

A&A

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We studied the accuracy, robustness, and self-consistency of pixel-domain simulations of the gravitational lensing effect on the primordial cosmic microwave background (CMB) anisotropies due to the large-scale structure of the Universe. In particular, we investigated the dependence of the precision of the results precision on some crucial parameters of these techniques and propose a semi-analytic framework to determine their values so that the required precision is a priori assured and the numerical workload simultaneously optimized. Our focus was on the B-mode signal, but we also discuss other CMB observables, such as the total intensity, T , and E-mode polarization, emphasizing differences and similarities between all these cases. Our semi-analytic considerations are backed up by extensive numerical results. Those are obtained using a code, nicknamed lenS 2 HAT -for lensing using scalable spherical harmonic transforms (S 2 HAT) -which we have developed in the course of this work. The code implements a version of the previously described pixel-domain approach and permits performing the simulations at very high resolutions and data volumes, thanks to its efficient parallelization provided by the S 2 HAT library -a parallel library for calculating of the spherical harmonic transforms. The code is made publicly available.

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Section: Discussionmentioning

confidence: 99%

High-precision simulations of the weak lensing effect on cosmic microwave background polarization

Fabbian

Stompor

2013

A&A

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“…The resulting lensed CMB temperature and polarization maps agree very well with the theoretical prediction (Carbone et al 2009). Using the results of Carbone et al (2008), Merkel & Schäfer (2011) showed that the small amount of non-Gaussianity present in the CMB lensing excursion angle has only a marginal effect on the lensed CMB spectra. In a recent study Carbone et al (2013) produced lensing deflection maps from N-body simulations in the framework of interacting dark energy cosmologies.…”

Section: Introductionmentioning

confidence: 99%

Extreme value statistics of cosmic microwave background lensing deflection angles

Merkel¹,

Schäfer²

2015

Mon. Not. R. Astron. Soc.

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The smaller the angular scales on which the anisotropies of the cosmic microwave background (CMB) are probed the more important their distortion due to gravitational lensing becomes. Here we investigate the maxima and minima of the CMB lensing deflection field using general extreme value statistics. Since general extreme value statistics applies to uncorrelated data in first place we consider appropriately low-pass filtered deflection maps. Besides the suppression of correlations filtering is required for another reason: The lensing field itself is not directly observable but needs to be (statistically) reconstructed from the lensed CMB by means of a quadratic estimator. This reconstruction, though, is noise dominated and therefore requires smoothing, too. In idealized Gaussian realizations as well as in realistically reconstructed data we find that both maxima and minima of the deflection angle components follow consistently a general extreme value distribution of Weibull-type. However, its shape, location and scale parameters vary significantly between different realizations. The statistics' potential power to constrain cosmological models appears therefore rather limited.

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“…The choice of max for each different shell is optimized to ensure the total deflection is computed with sub-percent precision for scales 8000.The magnification matrix follows straightforwardly from Eq. (21) as…”

Section: A Ray Tracing Algorithm For Cmb Lensingmentioning

confidence: 99%

“…The lensing potential, however, becomes non-Gaussian due to nonlinear structure formation mainly at late times. Although the level of non-Gaussianity is expected to be small due to the large number of potential wells that deflect CMB photons, the impact of this effect has to be quantified in light of future high-precision measurements [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…the correlation between subsequent lensing events) neglecting therefore some of the sources of non-Gaussian statistics in the lensing potential. Earlier attempts to model CMB lensing including the effects of nonlinear structure formation were presented in [21,24,25]. Recent works investigated the effect of the relaxation of the Born approximation on lensed CMB power spectra and CMB lensing power spectra, from both an analytical and a numerical point of view [23,[26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Lensing reconstruction in post-Born cosmic microwave background weak lensing

2018

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The study of the Cosmic Microwave Background (CMB) lensing potential has established itself by now as a robust way of probing the physics of large-scale structure growth. The most common estimators of the lensing potential are derived under the assumption of Gaussianity of the matter distribution and in the Born approximation of the photon diffusion. In this paper we study the performance of quadratic estimators when applied to realistic sky maps extracted from multiple-lens ray tracing techniques in cosmological N -body simulations. These are expected to model accurately the effects due to the non-Gaussianity of the matter distribution induced by its nonlinearity and the deviation from the Born approximation. We show that both these effects on their own lead to reconstruction biases, but these tend to partially cancel each other when both these effects are considered together. We forecast the impact of these biases on the estimation of cosmological parameters for future high-sensitivity CMB experiments like CMB-S4. We find that the cold dark matter density, Ω cdm , the optical depth to reionization τ , the amplitude of primordial inflationary perturbations, As and the sum of neutrino masses, Mν , could be biased at the 1-2σ level, if no external data set is used. We also observe a reduction of the bias if external data like baryon acoustic oscillations (BAO) is included.I.

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Gravitational lensing of the cosmic microwave background by non-linear structures

Cited by 9 publications

References 28 publications

High-precision simulations of the weak lensing effect on cosmic microwave background polarization

High-precision simulations of the weak lensing effect on cosmic microwave background polarization

Extreme value statistics of cosmic microwave background lensing deflection angles

Lensing reconstruction in post-Born cosmic microwave background weak lensing

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