Planck intermediate results Ade, P; Aghanim, N; Alves, M ...
Astronomy and astrophysics (Berlin),
02/2016, Letnik:
586
Journal Article
Recenzirano
Odprti dostop
Within ten nearby (d< 450pc) Gould belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized ...thermal emission of Galactic dust observed by Planck at 353GHz, and the gas column density structures, quantified by the gradient of the column density, N sub(H). The selected regions, covering several degrees in size, are analysed at an effective angular resolution of 10' FWHM, thus sampling physical scales from 0.4 to 40pc in the nearest cloud. The column densities in the selected regions range from N sub(H)approximate 10 super(21) to10 super(23)cm super(-2), and hence they correspond to the bulk of the molecular clouds. The relative orientation is evaluated pixel by pixel and analysed in bins of column density using the novel statistical tool called "histogram of relative orientations". Throughout this study, we assume that the polarized emission observed by Planck at 353GHz is representative of the projected morphology of the magnetic field in each region, i.e., we assume a constant dust grain alignment efficiency, independent of the local environment. Within most clouds we find that the relative orientation changes progressively with increasing N sub(H), from mostly parallel or having no preferred orientation to mostly perpendicular. In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfvenic or sub-Alfvenic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength with estimates we obtain from other methods and discuss the implications of the Planck observations for the general picture of molecular cloud formation and evolution.
Abstract
LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and ...fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun–Earth Lagrangian point L2, where it will map the cosmic microwave background polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of $2.2\, \mu$K-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions, and synergies with other projects.
We present the first measurement of the correlation between the map of the cosmic microwave background (CMB) lensing potential derived from the Planck nominal mission data and z≳1.5 galaxies detected ...by the Herschel-ATLAS (H-ATLAS) survey covering about 600 deg{sup 2}, i.e., about 1.4% of the sky. We reject the hypothesis that there is no correlation between CMB lensing and galaxy detection at a 20σ significance, checking the result by performing a number of null tests. The significance of the detection of the theoretically expected cross-correlation signal is found to be 10σ. The galaxy bias parameter, b, derived from a joint analysis of the cross-power spectrum and of the autopower spectrum of the galaxy density contrast is found to be b=2.80{sub −0.11}{sup +0.12}, consistent with earlier estimates for H-ATLAS galaxies at similar redshifts. On the other hand, the amplitude of the cross-correlation is found to be a factor 1.62 ± 0.16 higher than expected from the standard model and also found by cross-correlation analyses with other tracers of the large-scale structure. The enhancement due to lensing magnification can account for only a fraction of the excess cross-correlation signal. We suggest that part of it may be due to an incomplete removal of the contamination of the cosmic infrared background, which includes the H-ATLAS sources we are cross-correlating with. In any case, the highly significant detection reported here using a catalog covering only 1.4% of the sky demonstrates the potential of CMB lensing correlations with submillimeter surveys.
We present an overview of the design and status of the
Polarbear
-2 and the Simons Array experiments.
Polarbear
-2 is a cosmic microwave background polarimetry experiment which aims to characterize ...the arc-minute angular scale B-mode signal from weak gravitational lensing and search for the degree angular scale B-mode signal from inflationary gravitational waves. The receiver has a 365 mm diameter focal plane cooled to 270 mK. The focal plane is filled with 7588 dichroic lenslet–antenna-coupled polarization sensitive transition edge sensor (TES) bolometric pixels that are sensitive to 95 and 150 GHz bands simultaneously. The TES bolometers are read-out by SQUIDs with 40 channel frequency domain multiplexing. Refractive optical elements are made with high-purity alumina to achieve high optical throughput. The receiver is designed to achieve noise equivalent temperature of 5.8
μ
K
CMB
s
in each frequency band.
Polarbear
-2 will deploy in 2016 in the Atacama desert in Chile. The Simons Array is a project to further increase sensitivity by deploying three
Polarbear
-2 type receivers. The Simons Array will cover 95, 150, and 220 GHz frequency bands for foreground control. The Simons Array will be able to constrain tensor-to-scalar ratio and sum of neutrino masses to
σ
(
r
)
=
6
×
10
-
3
at
r
=
0.1
and
∑
m
ν
(
σ
=
1
)
to 40 meV.
Euclid preparation Bodendorf, C.; Grupp, F.; Hormuth, F. ...
Astronomy and astrophysics (Berlin),
06/2022, Letnik:
662
Journal Article
Recenzirano
Odprti dostop
Euclid
will be the first space mission to survey most of the extragalactic sky in the 0.95–2.02 µm range, to a 5
σ
point-source median depth of 24.4 AB mag. This unique photometric dataset will find ...wide use beyond
Euclid’s
core science. In this paper, we present accurate computations of the Euclid
Y
E
,
J
E
, and
H
E
passbands used by the Near-Infrared Spectrometer and Photometer (NISP), and the associated photometric system. We pay particular attention to passband variations in the field of view, accounting for, among other factors, spatially variable filter transmission and variations in the angle of incidence on the filter substrate using optical ray tracing. The response curves’ cut-on and cut-off wavelengths – and their variation in the field of view – are determined with ~0.8 nm accuracy, essential for the photometric redshift accuracy required by
Euclid.
After computing the photometric zero points in the AB mag system, we present linear transformations from and to common ground-based near-infrared photometric systems, for normal stars, red and brown dwarfs, and galaxies separately. A
Python
tool to compute accurate magnitudes for arbitrary passbands and spectral energy distributions is provided. We discuss various factors, from space weathering to material outgassing, that may slowly alter
Euclid
’s spectral response. At the absolute flux scale, the
Euclid
in-flight calibration program connects the NISP photometric system to
Hubble
Space Telescope spectrophotometric white dwarf standards; at the relative flux scale, the chromatic evolution of the response is tracked at the milli-mag level. In this way, we establish an accurate photometric system that is fully controlled throughout
Euclid’s
lifetime.
Planck intermediate results Adam, R; Ade, P A R; Alves, M I R ...
Astronomy and astrophysics (Berlin),
12/2016, Letnik:
596
Journal Article
Recenzirano
Odprti dostop
Recent models for the large-scale Galactic magnetic fields in the literature have been largely constrained by synchrotron emission and Faraday rotation measures. We use three different but ...representative models to compare their predicted polarized synchrotron and dust emission with that measured by the Planck satellite. We first update these models to match the Planck synchrotron products using a common model for the cosmic-ray leptons. We discuss the impact on this analysis of the ongoing problems of component separation in the Planck microwave bands and of the uncertain cosmic-ray spectrum. In particular, the inferred degree of ordering in the magnetic fields is sensitive to these systematic uncertainties, and we further show the importance of considering the expected variations in the observables in addition to their mean morphology. We then compare the resulting simulated emission to the observed dust polarization and find that the dust predictions do not match the morphology in the Planck data but underpredict the dust polarization away from the plane. We modify one of the models to roughly match both observables at high latitudes by increasing the field ordering in the thin disc near the observer. Though this specific analysis is dependent on the component separation issues, we present the improved model as a proof of concept for how these studies can be advanced in future using complementary information from ongoing and planned observational projects.
Context
. Component separation is the process with which emission sources in astrophysical maps are generally extracted by taking multi-frequency information into account. It is crucial to develop ...more reliable methods for component separation for future cosmic microwave background (CMB) experiments such as the Simons Observatory, the CMB-S4, or the LiteBIRD satellite.
Aims
. We aim to develop a machine learning method based on fully convolutional neural networks called the CMB extraction neural network (CENN) in order to extract the CMB signal in total intensity by training the network with realistic simulations. The frequencies we used are the
Planck
channels 143, 217, and 353 GHz, and we validated the neural network throughout the sky and at three latitude intervals: 0° < |
b
| < 5°, 5° < |
b
| < 30°, and 30° < |
b
| < 90°, Moreover, we used neither Galactic nor point-source (PS) masks.
Methods
. To train the neural network, we produced multi-frequency realistic simulations in the form of patches of 256 × 256 pixels that contained the CMB signal, the Galactic thermal dust, cosmic infrared background, and PS emissions, the thermal Sunyaev–Zel’dovich effect from galaxy clusters, and instrumental noise. After validating the network, we compared the power spectra from input and output maps. We analysed the power spectrum from the residuals at each latitude interval and throughout the sky, and we studied how our model handled high contamination at small scales.
Results
. We obtained a CMB power spectrum with a mean difference between input and output of 13 ± 113 µK
2
for multipoles up to above 4000. We computed the residuals, obtaining 700 ± 60 µK
2
for 0° < |
b
| < 5°, 80 ± 30 µK
2
for 5° < |
b
| < 30°, and 30 ± 20 µK
2
for 30° < |
b
| < 90° for multipoles up to above 4000. For the entire sky, we obtained 30 ± 10 µK
2
for
l
≤ 1000 and 20 ± 10 µK
2
for
l
≤ 4000. We validated the neural network in a single patch with strong contamination at small scales, obtaining a difference between input and output of 50 ± 120 µK
2
and residuals of 40 ± 10 µK
2
up to
l
~ 2500. In all cases, the uncertainty of each measure was taken as the standard deviation.
Conclusions
. The results show that fully convolutional neural networks are promising methods for performing component separation in future CMB experiments. Moreover, we show that CENN is reliable against different levels of contamination from Galactic and PS foregrounds at both large and small scales.
ABSTRACT
We present the application of the fast independent component analysis (fastica) technique for blind component separation to polarized astrophysical emission. We study how the cosmic ...microwave background (CMB) polarized signal, consisting of E and B modes, can be extracted from maps affected by substantial contamination from diffuse Galactic foreground emission and instrumental noise. We implement Monte Carlo chains varying the CMB and noise realizations in order to asses the average capabilities of the algorithm and their variance. We perform the analysis of all‐sky maps simulated according to the Planck satellite capabilities, modelling the sky signal as a superposition of the CMB and of the existing simulated polarization templates of Galactic synchrotron. Our results indicate that the angular power spectrum of CMB E mode can be recovered on all scales up to ℓ≃ 1000, corresponding to the fourth acoustic oscillation, while the B‐mode power spectrum can be detected, up to its turnover at ℓ≃ 100, if the ratio of tensor to scalar contributions to the temperature quadrupole exceeds 30 per cent. The power spectrum of the cross‐correlation between total intensity and polarization, TE, can be recovered up to ℓ≃ 1200, corresponding to the seventh TE acoustic oscillation.
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