Aims. We present for the first time a coherent model of the polarized Galactic synchrotron and thermal dust emissions that are likely to form the predominant diffuse foregrounds for measuring the ...polarized CMB fluctuations by the Planck satellite mission. Methods. We produced 3D models of the Galactic magnetic field including regular and turbulent components, and of the distribution of matter in the Galaxy including relativistic electron and dust grain components. By integrating along the line of sight, we constructed maps of the polarized Galactic synchrotron and thermal dust emission for each of these models and compared them to currently available data. We consider the 408 MHz all-sky continuum survey, the 23 GHz band of the Wilkinson Microwave Anisotropy Probe, and the 353 GHz Archeops data. Results. The best-fit parameters obtained are consistent with previous estimates in the literature based only on synchrotron emission and pulsar rotation measurements and this allows us to reproduce the large-scale features observed in the data. Unmodeled local Galactic structures and the effect of turbulence make it difficult to accurately reconstruct observations in the Galactic plane. Conclusions. Finally, using the best-fit model we are able to estimate the expected polarized foreground contamination at the Planck frequency bands. For the CMB bands, 70, 100, 143 and 217 GHz, at high Galactic latitudes although the CMB signal dominates in general, a significant foreground contribution is expected at large angular scales. In particular, this contribution will dominate the CMB signal for the B modes expected from realistic models of a background of primordial gravitational waves.
Context. Based on recent observations of the cosmic microwave background (CMB), claims of statistical anomalies in the properties of the CMB fluctuations have been made. Although the statistical ...significance of the anomalies remains only at the ∼2−3σ significance level, the fact that there are many different anomalies, several of which support a possible deviation from statistical isotropy, has motivated a search for models that provide a common mechanism to generate them. Aims. The goal of this paper is to investigate whether these anomalies could originate from non-Gaussian cosmological models, and to determine what properties these models should have. Methods. We present a simple isotropic, non-Gaussian class of toy models that can reproduce six of the most extensively studied anomalies. We compare the presence of anomalies found in simulated maps generated from the toy models and from a standard model with Gaussian fluctuations. Results. We show that the following anomalies, as found in the Planck data, commonly occur in the toy model maps: (1) large-scale hemispherical asymmetry (large-scale dipolar modulation), (2) small-scale hemispherical asymmetry (alignment of the spatial distribution of CMB power over all scales ℓ = 2, 1500), (3) a strongly non-Gaussian hot or cold spot, (4) a low power spectrum amplitude for ℓ < 30, including specifically (5) a low quadrupole and an unusual alignment between the quadrupole and the octopole, and (6) parity asymmetry of the lowest multipoles. We note that this class of toy model resembles models of primordial non-Gaussianity characterised by strongly scale-dependent gNL-like trispectra.
The three Minkowski functionals and the recently defined length of the skeleton are estimated for the co-added first-year Wilkinson Microwave Anisotropy Probe (WMAP) data and compared with 5000 Monte ...Carlo simulations, based on Gaussian fluctuations with the a priori best-fit running- index power spectrum and WMAP-like beam and noise properties. Several power spectrum-dependent quantities, such as the number of stationary points, the total length of the skeleton, and a spectral parameter, gamma, are also estimated. While the area and length Minkowski functionals and the length of the skeleton show no evidence for departures from the Gaussian hypothesis, the northern hemisphere genus has a Chi super(2) that is large at the 95% level for all scales. For the particular smoothing scale of 3 degree 40 FWHM it is larger than that found in 99.5% of the simulations. In addition, the WMAP genus for negative thresholds in the northern hemisphere has an amplitude that is larger than in the simulations with a significance of more than 3 capital sigma . On the smallest angular scales considered, the number of extrema in the WMAP data is high at the 3 capital sigma level. However, this can probably be attributed to the effect of point sources. Finally, the spectral parameter gamma is high at the 99% level in the northern Galactic hemisphere, while perfectly acceptable in the southern hemisphere. The results provide strong evidence for the presence of both non-Gaussian behavior and an unexpected power asymmetry between the northern and southern hemispheres in the WMAP data.
Abstract
Anomalous microwave emission at 20-40 GHz has been detected across our Galactic sky. It is highly correlated with thermal dust emission and hence it is thought to be due to spinning dust ...grains. Alternatively, this emission could be due to synchrotron radiation with a flattening (hard) spectral index. We cross-correlate synchrotron, free-free and thermal dust templates with the Wilkinson Microwave Anisotropy Probe (WMAP) 7-year maps using synchrotron templates at both 408 MHz and 2.3 GHz to assess the amount of flat synchrotron emission that is present, and the impact that this has on the correlations with the other components. We find that there is only a small amount of flattening visible in the synchrotron spectral indices by 2.3 GHz, of around Δβ; ≈ 0.05, and that the significant level of dust-correlated emission in the lowest WMAP bands is largely unaffected by the choice of synchrotron template, particularly at high latitudes (it decreases by only ∼7 per cent when using 2.3 GHz rather than 408 MHz). This agrees with expectation if the bulk of the anomalous emission is generated by spinning dust grains.
Abstract
Recent analyses of the Wilkinson Microwave Anisotropy Probe (WMAP) data have suggested that the low-order multipoles of the cosmic microwave background (CMB) anisotropy distribution show ...cosmologically interesting and unexpected morphologies and amplitudes. In this paper, we apply a power equalization (PE) filter to the high-latitude WMAP data in order to reconstruct these low-ℓ multipoles free from the largest Galactic foreground modelling uncertainties in the Galactic plane. The characteristic spatial distributions of the modes of order ℓ= 2, 3, 4, 5 have been determined as a function of frequency, sky coverage and two methods for foreground correction: using the template-based corrections of Bennett et al. and by a simple linear projection scheme assuming the spectral dependence of the foreground components. Although the derived multipole maps are statistically consistent with previous estimates from Tegmark, de Oliveira-Costa & Hamilton (TOH) and Efstathiou, our analyses suggest that the K and Ka frequency bands remain significantly contaminated by residual foreground emission for the WMAP Kp2 mask. However, the ℓ= 3, 4, 5 multipole maps for the Q, V and W channels indicate that, after foreground cleaning, these multipoles are dominated by the CMB anisotropy component. We confirm the TOH result that the octopole does indeed show structure in which its hot and cold spots are centred on a single plane in the sky, and show further that this is very stable with respect to the applied mask and foreground correction. The estimated quadrupole is much less stable showing non-negligible dependence on the Galactic foreground correction. Including these uncertainties is likely to weaken the statistical significance of the claimed alignment between the quadrupole and octopole. Nevertheless, these anisotropy patterns are also present in the COBE-DMR data and are unlikely to be associated with instrumental systematic artefacts.
Exploring cosmic origins with CORE: The instrument de Bernardis, P.; Ade, P.A.R.; Baselmans, J.J.A. ...
Journal of cosmology and astroparticle physics,
04/2018, Letnik:
2018, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We describe a space-borne, multi-band, multi-beam polarimeter aiming at a precise and accurate measurement of the polarization of the Cosmic Microwave Background. The instrument is optimized to be ...compatible with the strict budget requirements of a medium-size space mission within the Cosmic Vision Programme of the European Space Agency. The instrument has no moving parts, and uses arrays of diffraction-limited Kinetic Inductance Detectors to cover the frequency range from 60 GHz to 600 GHz in 19 wide bands, in the focal plane of a 1.2 m aperture telescope cooled at 40 K, allowing for an accurate extraction of the CMB signal from polarized foreground emission. The projected CMB polarization survey sensitivity of this instrument, after foregrounds removal, is 1.7 μK⋅arcmin. The design is robust enough to allow, if needed, a downscoped version of the instrument covering the 100 GHz to 600 GHz range with a 0.8 m aperture telescope cooled at 85 K, with a projected CMB polarization survey sensitivity of 3.2 μK⋅arcmin.
We present further investigations of the Wilkinson Microwave Anisotropy Probe (WMAP) data by means of the Minkowski functionals and the scaling index method. In order to test for non-Gaussianities ...(NGs) with respect to scale dependences, we use the so-called surrogate maps, in which possible phase correlations of the Fourier phases of the original WMAP data and the simulations, respectively, are destroyed by applying a shuffling scheme to the maps. A statistical comparison of the original maps with the surrogate maps then allows us to test for the existence of higher order correlations (HOCs) in the original maps, also and especially on well-defined Fourier modes.
We calculate the σ-normalized deviation between the Minkowski functionals of original data and 500 surrogates for different hemispheres in the sky and find ecliptic hemispherical asymmetries between the northern and southern ecliptic sky. Using Minkowski functionals as an image analysis technique sensitive to HOCs, we find deviations from Gaussianity in the WMAP data with an empirical probability p > 99.8 per cent when considering the low -range with Δ = 2, 20. The analysis technique of the scaling indices leads to the same results for this -interval with a slightly lower deviation but still at p > 99.8 per cent. Although the underlying foreground reduction methods of the maps differ from each other, we find similar results for the WMAP seven-year internal linear combination map and the WMAP seven-year needlet-based ILC map for deviations from Gaussianity in the low -range. Our results point once more to a cosmological nature of the signal. For a higher -range with Δ = 120, 300, the results differ between the two image analysis techniques and between the two maps which makes an intrinsic nature of the signal on this -range less likely. When we decrease the size of the analysed sky regions for the low- study, we do not find signatures of NG in the northern ecliptic sky. In the south, we find individual spots which show deviations from Gaussianity.
In addition, we investigate non-Gaussian cosmic microwave background simulations that depend on the f
NL parameter of the local type. These simulations with f
local
NL = 0, ±100, ±1000 cannot account for the detected signatures on the low -range.
This paper presents an overview of the polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse maps of dust ...polarization fraction and polarization angle at 1° resolution, taking into account noise bias and possible systematic effects. The sensitivity of the Planck HFI polarization measurements allows for the first time a mapping of Galactic dust polarized emission on large scales, including low column density regions. We find that the maximum observed dust polarization fraction is high (pmax = 19.8%), in particular in some regions of moderate hydrogen column density (NH < 2 × 1021 cm-2). The polarization fraction displays a large scatter at NH below a few 1021 cm-2. There is a general decrease in the dust polarization fraction with increasing column density above NH ≃ 1 × 1021 cm-2 and in particular a sharp drop above NH ≃ 1.5 × 1022 cm-2. We characterize the spatial structure of the polarization angle using the angle dispersion function. We find that the polarization angle is ordered over extended areas of several square degrees, separated by filamentary structures of high angle dispersion function. These appear as interfaces where the sky projection of the magnetic field changes abruptly without variations in the column density. The polarization fraction is found to be anti-correlated with the dispersion of polarization angles. These results suggest that, at the resolution of 1°, depolarization is due mainly to fluctuations in the magnetic field orientation along the line of sight, rather than to the loss of grain alignment in shielded regions. We also compare the polarization of thermal dust emission with that of synchrotron measured with Planck, low-frequency radio data, and Faraday rotation measurements toward extragalactic sources. These components bear resemblance along the Galactic plane and in some regions such as the Fan and North Polar Spur regions. The poor match observed in other regions shows, however, that dust, cosmic-ray electrons, and thermal electrons generally sample different parts of the line of sight.
Wilkinson Microwave Anisotropy Probe (WMAP) data when combined with ancillary data on free-free, synchrotron and dust allow an improved understanding of the spectrum of emission from each of these ...components. Here we examine the sky variation at intermediate and high latitudes using a cross-correlation technique. In particular, we compare the observed emission in several global partitions of the sky plus 33 selected sky regions to three 'standard' templates. The regions are selected using a criterion based on the morphology of these template maps.
The synchrotron emission shows evidence of steepening between GHz frequencies and the WMAP bands. There are indications of spectral index variations across the sky, but the current data are not precise enough to accurately quantify this from region to region.
The Hα template correlated emission derived from the global fits shows clear evidence of deviation from a free-free spectrum. If this spectrum is decomposed into a contribution from both free-free and spinning dust emission in the warm ionized medium of the Galaxy, the derived free-free emissivity corresponds to a mean electron temperature of ∼6000 K (a value critically dependent on the impact of dust absorption on the Hα intensity), and the spinning dust emission has a peak emission in intensity typically in the range 40-50 GHz. However, the analysis of the smaller regions is generally unrevealing and the analysis presented here does not unambiguously demonstrate the presence of spinning dust emission in the warm ionized medium, as advocated by Dobler & Finkbeiner.
The anomalous microwave emission associated with dust is detected at high significance in most of the 33 fields studied. The anomalous emission correlates well with the Finkbeiner et al. model 8 predictions (FDS8) at 94 GHz, and is well described globally by a power-law emission model with an effective spectral index between 20 and 60 GHz of β≈−2.7. It is clear that attempts to explain the emission by spinning dust models require multiple components, which presumably relates to a complex mix of emission regions along a given line of sight. An enhancement of the thermal dust contribution over the FDS8 predictions by a factor ∼1.2 is required with such models. Furthermore, the emissivity varies by a factor of ∼50 per cent from cloud to cloud relative to the mean.
The significance of these results for the correction of cosmic microwave background data for Galactic foreground emission is discussed.
Planck 2018 results Akrami, Y.; Aumont, J.; Baccigalupi, C. ...
Astronomy and astrophysics (Berlin),
09/2020, Letnik:
641
Journal Article
Recenzirano
Odprti dostop
We report on the implications for cosmic inflation of the 2018 release of the
Planck
cosmic microwave background (CMB) anisotropy measurements. The results are fully consistent with those reported ...using the data from the two previous
Planck
cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles.
Planck
temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be
n
s
= 0.9649 ± 0.0042 at 68% CL. We find no evidence for a scale dependence of
n
s
, either as a running or as a running of the running. The Universe is found to be consistent with spatial flatness with a precision of 0.4% at 95% CL by combining
Planck
with a compilation of baryon acoustic oscillation data. The
Planck
95% CL upper limit on the tensor-to-scalar ratio,
r
0.002
< 0.10, is further tightened by combining with the BICEP2/Keck Array BK15 data to obtain
r
0.002
< 0.056. In the framework of standard single-field inflationary models with Einstein gravity, these results imply that: (a) the predictions of slow-roll models with a concave potential,
V
″(
ϕ
) < 0, are increasingly favoured by the data; and (b) based on two different methods for reconstructing the inflaton potential, we find no evidence for dynamics beyond slow roll. Three different methods for the non-parametric reconstruction of the primordial power spectrum consistently confirm a pure power law in the range of comoving scales 0.005 Mpc
−1
≲
k
≲ 0.2 Mpc
−1
. A complementary analysis also finds no evidence for theoretically motivated parameterized features in the
Planck
power spectra. For the case of oscillatory features that are logarithmic or linear in
k
, this result is further strengthened by a new combined analysis including the
Planck
bispectrum data. The new
Planck
polarization data provide a stringent test of the adiabaticity of the initial conditions for the cosmological fluctuations. In correlated, mixed adiabatic and isocurvature models, the non-adiabatic contribution to the observed CMB temperature variance is constrained to 1.3%, 1.7%, and 1.7% at 95% CL for cold dark matter, neutrino density, and neutrino velocity, respectively.
Planck
power spectra plus lensing set constraints on the amplitude of compensated cold dark matter-baryon isocurvature perturbations that are consistent with current complementary measurements. The polarization data also provide improved constraints on inflationary models that predict a small statistically anisotropic quadupolar modulation of the primordial fluctuations. However, the polarization data do not support physical models for a scale-dependent dipolar modulation. All these findings support the key predictions of the standard single-field inflationary models, which will be further tested by future cosmological observations.
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