Planck intermediate results Akrami, Y.; Andersen, K. J.; Baccigalupi, C. ...
Astronomy and astrophysics (Berlin),
11/2020, Letnik:
643
Journal Article
Recenzirano
Odprti dostop
We present the
NPIPE
processing pipeline, which produces calibrated frequency maps in temperature and polarization from data from the
Planck
Low Frequency Instrument (LFI) and High Frequency ...Instrument (HFI) using high-performance computers.
NPIPE
represents a natural evolution of previous
Planck
analysis efforts, and combines some of the most powerful features of the separate LFI and HFI analysis pipelines. For example, following the LFI 2018 processing procedure,
NPIPE
uses foreground polarization priors during the calibration stage in order to break scanning-induced degeneracies. Similarly,
NPIPE
employs the HFI 2018 time-domain processing methodology to correct for bandpass mismatch at all frequencies. In addition,
NPIPE
introduces several improvements, including, but not limited to: inclusion of the 8% of data collected during repointing manoeuvres; smoothing of the LFI reference load data streams; in-flight estimation of detector polarization parameters; and construction of maximally independent detector-set split maps. For component-separation purposes, important improvements include: maps that retain the CMB Solar dipole, allowing for high-precision relative calibration in higher-level analyses; well-defined single-detector maps, allowing for robust CO extraction; and HFI temperature maps between 217 and 857 GHz that are binned into 0′.9 pixels (
N
side
= 4096), ensuring that the full angular information in the data is represented in the maps even at the highest
Planck
resolutions. The net effect of these improvements is lower levels of noise and systematics in both frequency and component maps at essentially all angular scales, as well as notably improved internal consistency between the various frequency channels. Based on the
NPIPE
maps, we present the first estimate of the Solar dipole determined through component separation across all nine
Planck
frequencies. The amplitude is (3366.6 ± 2.7)
μ
K, consistent with, albeit slightly higher than, earlier estimates. From the large-scale polarization data, we derive an updated estimate of the optical depth of reionization of
τ
= 0.051 ± 0.006, which appears robust with respect to data and sky cuts. There are 600 complete signal, noise and systematics simulations of the full-frequency and detector-set maps. As a
Planck
first, these simulations include full time-domain processing of the beam-convolved CMB anisotropies. The release of
NPIPE
maps and simulations is accompanied with a complete suite of raw and processed time-ordered data and the software, scripts, auxiliary data, and parameter files needed to improve further on the analysis and to run matching simulations.
We theoretically and observationally investigate different choices of initial conditions for the primordial mode function that are imposed during an epoch preceding inflation. By deriving predictions ...for the observables resulting from several alternate quantum vacuum prescriptions we show some choices of vacua are theoretically observationally distinguishable from others. Comparing these predictions to the Planck 2018 observations via a Bayesian analysis shows no significant evidence to favour any of the quantum vacuum prescriptions over the others. In addition we consider frozen initial conditions, representing a white-noise initial state at the big-bang singularity. Under certain assumptions the cosmological concordance model and frozen initial conditions are found to produce identical predictions for the cosmic microwave background anisotropies. Frozen initial conditions may thus provide an alternative theoretic paradigm to explain observations that were previously understood in terms of the inflation of a quantum vacuum.
Planck 2018 results Aghanim, N.; Akrami, Y.; Aumont, J. ...
Astronomy and astrophysics (Berlin),
09/2020, Letnik:
641
Journal Article
Recenzirano
Odprti dostop
This paper presents the High Frequency Instrument (HFI) data processing procedures for the
Planck
2018 release. Major improvements in mapmaking have been achieved since the previous
Planck
2015 ...release, many of which were used and described already in an intermediate paper dedicated to the
Planck
polarized data at low multipoles. These improvements enabled the first significant measurement of the reionization optical depth parameter using
Planck
-HFI data. This paper presents an extensive analysis of systematic effects, including the use of end-to-end simulations to facilitate their removal and characterize the residuals. The polarized data, which presented a number of known problems in the 2015
Planck
release, are very significantly improved, especially the leakage from intensity to polarization. Calibration, based on the cosmic microwave background (CMB) dipole, is now extremely accurate and in the frequency range 100–353 GHz reduces intensity-to-polarization leakage caused by calibration mismatch. The Solar dipole direction has been determined in the three lowest HFI frequency channels to within one arc minute, and its amplitude has an absolute uncertainty smaller than 0.35
μ
K, an accuracy of order 10
−4
. This is a major legacy from the
Planck
HFI for future CMB experiments. The removal of bandpass leakage has been improved for the main high-frequency foregrounds by extracting the bandpass-mismatch coefficients for each detector as part of the mapmaking process; these values in turn improve the intensity maps. This is a major change in the philosophy of “frequency maps”, which are now computed from single detector data, all adjusted to the same average bandpass response for the main foregrounds. End-to-end simulations have been shown to reproduce very well the relative gain calibration of detectors, as well as drifts within a frequency induced by the residuals of the main systematic effect (analogue-to-digital convertor non-linearity residuals). Using these simulations, we have been able to measure and correct the small frequency calibration bias induced by this systematic effect at the 10
−4
level. There is no detectable sign of a residual calibration bias between the first and second acoustic peaks in the CMB channels, at the 10
−3
level.
Planck 2018 results Akrami, Y.; Ashdown, M.; Aumont, J. ...
Astronomy and astrophysics (Berlin),
09/2020, Letnik:
641
Journal Article
Recenzirano
Odprti dostop
The study of polarized dust emission has become entwined with the analysis of the cosmic microwave background (CMB) polarization in the quest for the curl-like
B
-mode polarization from primordial ...gravitational waves and the low-multipole
E
-mode polarization associated with the reionization of the Universe. We used the new
Planck
PR3 maps to characterize Galactic dust emission at high latitudes as a foreground to the CMB polarization and use end-to-end simulations to compute uncertainties and assess the statistical significance of our measurements. We present
Planck
EE
,
BB
, and
TE
power spectra of dust polarization at 353 GHz for a set of six nested high-Galactic-latitude sky regions covering from 24 to 71% of the sky. We present power-law fits to the angular power spectra, yielding evidence for statistically significant variations of the exponents over sky regions and a difference between the values for the
EE
and
BB
spectra, which for the largest sky region are
α
E
E
= −2.42 ± 0.02 and
α
B
B
= −2.54 ± 0.02, respectively. The spectra show that the
TE
correlation and
E/B
power asymmetry discovered by
Planck
extend to low multipoles that were not included in earlier
Planck
polarization papers due to residual data systematics. We also report evidence for a positive
TB
dust signal. Combining data from
Planck
and WMAP, we have determined the amplitudes and spectral energy distributions (SEDs) of polarized foregrounds, including the correlation between dust and synchrotron polarized emission, for the six sky regions as a function of multipole. This quantifies the challenge of the component-separation procedure that is required for measuring the low-
ℓ
reionization CMB
E
-mode signal and detecting the reionization and recombination peaks of primordial CMB
B
modes. The SED of polarized dust emission is fit well by a single-temperature modified black-body emission law from 353 GHz to below 70 GHz. For a dust temperature of 19.6 K, the mean dust spectral index for dust polarization is
β
d
P
= 1.53±0.02. The difference between indices for polarization and total intensity is
β
d
P
−
β
d
I
= 0.05±0.03. By fitting multi-frequency cross-spectra between
Planck
data at 100, 143, 217, and 353 GHz, we examine the correlation of the dust polarization maps across frequency. We find no evidence for a loss of correlation and provide lower limits to the correlation ratio that are tighter than values we derive from the correlation of the 217- and 353 GHz maps alone. If the
Planck
limit on decorrelation for the largest sky region applies to the smaller sky regions observed by sub-orbital experiments, then frequency decorrelation of dust polarization might not be a problem for CMB experiments aiming at a primordial
B
-mode detection limit on the tensor-to-scalar ratio
r
≃ 0.01 at the recombination peak. However, the
Planck
sensitivity precludes identifying how difficult the component-separation problem will be for more ambitious experiments targeting lower limits on
r
.
The myelin proteolipid protein (PLP) gene (i.e., the PLP/DM20 gene) has been of some interest because of its role in certain human demyelinating diseases, such as Pelizaeus-Merzbacher disease. A ...substantial amount of evidence, including neuronal pathology in knock-out and transgenic animals, suggests the gene also has functions unrelated to myelin structure, but the products of the gene responsible for these putative functions have not yet been identified. Here we report the identification of a new exon of the PLP/DM20 gene and at least two new products of the gene that contain this exon. The new exon, located between exons 1 and 2, is spliced into PLP and DM20 mRNAs creating a new translation initiation site that generates PLP and DM20 proteins with a 12 amino acid leader sequence. This leader sequence appears to target these proteins to a different cellular compartment within the cell bodies of oligodendrocytes and away from the myelin membranes. Furthermore, these new products are also expressed in a number of neuronal populations within the postnatal mouse brain, including the cerebellum, hippocampus, and olfactory system. We term these products somal-restricted PLP and DM20 proteins to distinguish them from the classic PLP and DM20 proteolipids. They represent putative candidates for some of the nonmyelin-related functions of the PLP/DM20 gene.
We demonstrate that the Bayesian evidence can be used to find a good approximation of the ground truth likelihood function of a dataset, a goal of the likelihood-free inference (LFI) paradigm. As a ...concrete example, we use forward modelled sky-averaged 21-cm signal antenna temperature datasets where we artificially inject noise structures of various physically motivated forms. We find that the Gaussian likelihood performs poorly when the noise distribution deviates from the Gaussian case, for example, heteroscedastic radiometric or heavy-tailed noise. For these non-Gaussian noise structures, we show that the generalised normal likelihood is on a similar Bayesian evidence scale with comparable sky-averaged 21-cm signal recovery as the ground truth likelihood function of our injected noise. We therefore propose the generalised normal likelihood function as a good approximation of the true likelihood function if the noise structure is a priori unknown.
Kinetic initial conditions for inflation Handley, W. J.; Brechet, S. D.; Lasenby, A. N. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
03/2014, Letnik:
89, Številka:
6
Journal Article
Odprti dostop
We consider the classical evolution of the inflaton field varphi(t) and the Hubble parameter H(t) in homogeneous and isotropic single-field inflation models. Under an extremely broad assumption, we ...show that the Universe generically emerges from an initial singularity in a noninflating state where the kinetic energy of the inflaton dominates its potential energy, varphi super(2) >> V(varphi). In this kinetically dominated regime, the dynamical equations admit simple analytic solutions for varphi(t) and H(t), which are independent of the form of V(varphi). In such models, these analytic solutions thus provide a simple way of setting the initial conditions from which to start the (usually numerical) integration of the coupled equations of motion for varphi(t) and H(t). We illustrate this procedure by applying it to spatially flat models with polynomial and exponential potentials, and determine the background evolution in each case; generically H(t) and varphi(t) as well as their time derivatives decrease during kinetic dominance until varphi super(2) ~ V(varphi), marking the onset of a brief period of fast-roll inflation prior to a slow-roll phase. We also calculate the approximate spectrum of scalar perturbations produced in each model and show that it exhibits a generic damping of power on large scales. This may be relevant to the apparent low-l falloff in the cosmic microwave background power spectrum.
Planck 2018 results Aghanim, N.; Akrami, Y.; Ashdown, M. ...
Astronomy and astrophysics (Berlin),
09/2020, Letnik:
641
Journal Article
Recenzirano
Odprti dostop
Observations of the submillimetre emission from Galactic dust, in both total intensity
I
and polarization, have received tremendous interest thanks to the
Planck
full-sky maps. In this paper we make ...use of such full-sky maps of dust polarized emission produced from the third public release of
Planck
data. As the basis for expanding on astrophysical studies of the polarized thermal emission from Galactic dust, we present full-sky maps of the dust polarization fraction
p
, polarization angle
ψ
, and dispersion function of polarization angles . The joint distribution (one-point statistics) of
p
and
N
H
confirms that the mean and maximum polarization fractions decrease with increasing
N
H
. The uncertainty on the maximum observed polarization fraction,
p
max
= 22.0
−1.4
+3.5
% at 353 GHz and 80′ resolution, is dominated by the uncertainty on the Galactic emission zero level in total intensity, in particular towards diffuse lines of sight at high Galactic latitudes. Furthermore, the inverse behaviour between
p
and found earlier is seen to be present at high latitudes. This follows the ∝
p
−1
relationship expected from models of the polarized sky (including numerical simulations of magnetohydrodynamical turbulence) that include effects from only the topology of the turbulent magnetic field, but otherwise have uniform alignment and dust properties. Thus, the statistical properties of
p
,
ψ
, and for the most part reflect the structure of the Galactic magnetic field. Nevertheless, we search for potential signatures of varying grain alignment and dust properties. First, we analyse the product map ×
p
, looking for residual trends. While the polarization fraction
p
decreases by a factor of 3−4 between
N
H
= 10
20
cm
−2
and
N
H
= 2 × 10
22
cm
−2
, out of the Galactic plane, this product ×
p
only decreases by about 25%. Because is independent of the grain alignment efficiency, this demonstrates that the systematic decrease in
p
with
N
H
is determined mostly by the magnetic-field structure and not by a drop in grain alignment. This systematic trend is observed both in the diffuse interstellar medium (ISM) and in molecular clouds of the Gould Belt. Second, we look for a dependence of polarization properties on the dust temperature, as we would expect from the radiative alignment torque (RAT) theory. We find no systematic trend of ×
p
with the dust temperature
T
d
, whether in the diffuse ISM or in the molecular clouds of the Gould Belt. In the diffuse ISM, lines of sight with high polarization fraction
p
and low polarization angle dispersion tend, on the contrary, to have colder dust than lines of sight with low
p
and high . We also compare the
Planck
thermal dust polarization with starlight polarization data in the visible at high Galactic latitudes. The agreement in polarization angles is remarkable, and is consistent with what we expect from the noise and the observed dispersion of polarization angles in the visible on the scale of the
Planck
beam. The two polarization emission-to-extinction ratios,
R
P
/
p
and
R
S/V
, which primarily characterize dust optical properties, have only a weak dependence on the column density, and converge towards the values previously determined for translucent lines of sight. We also determine an upper limit for the polarization fraction in extinction,
p
V
/
E
(
B
−
V
), of 13% at high Galactic latitude, compatible with the polarization fraction
p
≈ 20% observed at 353 GHz. Taken together, these results provide strong constraints for models of Galactic dust in diffuse gas.
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