scholarly journals Optimal strategy for polarization modulation in the LSPE-SWIPE experiment

2018 ◽  
Vol 609 ◽  
pp. A52 ◽  
Author(s):  
A. Buzzelli ◽  
P. de Bernardis ◽  
S. Masi ◽  
N. Vittorio ◽  
G. de Gasperis
Keyword(s):  
Power Spectrum ◽  
Polarization Modulation ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Half Wave ◽  
Wide Range ◽  
Cmb Polarization ◽  
Systematic Effects ◽  
Single Detector ◽  
Frequency Map

Context. Cosmic microwave background (CMB) B-mode experiments are required to control systematic effects with an unprecedented level of accuracy. Polarization modulation by a half wave plate (HWP) is a powerful technique able to mitigate a large number of the instrumental systematics. Aims. Our goal is to optimize the polarization modulation strategy of the upcoming LSPE-SWIPE balloon-borne experiment, devoted to the accurate measurement of CMB polarization at large angular scales. Methods. We departed from the nominal LSPE-SWIPE modulation strategy (HWP stepped every 60 s with a telescope scanning at around 12 deg/s) and performed a thorough investigation of a wide range of possible HWP schemes (either in stepped or continuously spinning mode and at different azimuth telescope scan-speeds) in the frequency, map and angular power spectrum domain. In addition, we probed the effect of high-pass and band-pass filters of the data stream and explored the HWP response in the minimal case of one detector for one operation day (critical for the single-detector calibration process). We finally tested the modulation performance against typical HWP-induced systematics. Results. Our analysis shows that some stepped HWP schemes, either slowly rotating or combined with slow telescope modulations, represent poor choices. Moreover, our results point out that the nominal configuration may not be the most convenient choice. While a large class of spinning designs provides comparable results in terms of pixel angle coverage, map-making residuals and BB power spectrum standard deviations with respect to the nominal strategy, we find that some specific configurations (e.g., a rapidly spinning HWP with a slow gondola modulation) allow a more efficient polarization recovery in more general real-case situations. Conclusions. Although our simulations are specific to the LSPE-SWIPE mission, the general outcomes of our analysis can be easily generalized to other CMB polarization experiments.

scholarly journals Improved constraints on reionisation from CMB observations: A parameterisation of the kSZ effect

2020 ◽  
Vol 640 ◽  
pp. A90
Author(s):  
A. Gorce ◽  
S. Ilić ◽  
M. Douspis ◽  
D. Aubert ◽  
M. Langer
Keyword(s):  
Power Spectrum ◽  
Light Sources ◽  
Microwave Background ◽  
Free Electrons ◽  
Angular Power Spectrum ◽  
Intensity Mapping ◽  
Wide Range ◽  
Simple Scaling ◽  
Hydrodynamical Simulations ◽  
Two Parameters

We show that, in the context of patchy reionisation, an accurate description of the angular power spectrum of the kinetic Sunyaev–Zel’dovich (kSZ) effect is not possible with simple scaling relations between the amplitude of the spectrum and global parameters, such as the reionisation midpoint and its duration. We introduce a new parameterisation of this spectrum, based on a novel description of the power spectrum of the free electrons density contrast Pee(k, z) in terms of the reionisation global history and morphology. We directly relate features of the spectrum to the typical ionised bubble size at different stages in the process and, subsequently, to the angular scale at which the patchy kSZ power spectrum reaches its maximum. We successfully calibrated our results on a custom set of advanced radiative hydrodynamical simulations and later found our parameterisation to be a valid description of a wide range of other simulations and, therefore, reionisation physics. In the end, and as long as the global reionisation history is known, two parameters are sufficient to derive the angular power spectrum. Such an innovative framework applied to cosmic microwave background data and combined with 21 cm intensity mapping will allow a first consistent detection of the amplitude and shape of the patchy kSZ signal, giving in turn access to the physics of early light sources.

scholarly journals Clustering properties of TGSS radio sources

2019 ◽  
Vol 623 ◽  
pp. A148 ◽  
Author(s):  
Arianna Dolfi ◽  
Enzo Branchini ◽  
Maciej Bilicki ◽  
Andrés Balaguera-Antolínez ◽  
Isabella Prandoni ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Angular Spectrum ◽  
Radio Sources ◽  
Angular Power Spectrum ◽  
Sky Survey ◽  
Systematic Effects ◽  
Angular Correlation Function ◽  
Multiple Component ◽  
Anomalous Nature

We investigate the clustering properties of radio sources in the Alternative Data Release 1 of the TIFR GMRT Sky Survey (TGSS), focusing on large angular scales, where previous analyses have detected a large clustering signal. After appropriate data selection, the TGSS sample we use contains ∼110 000 sources selected at 150 MHz over ∼70% of the sky. The survey footprint is largely superimposed on that of the NRAO VLA Sky Survey (NVSS) with the majority of TGSS sources having a counterpart in the NVSS sample. These characteristics make TGSS suitable for large-scale clustering analyses and facilitate the comparison with the results of previous studies. In this analysis we focus on the angular power spectrum, although the angular correlation function is also computed to quantify the contribution of multiple-component radio sources. We find that on large angular scales, corresponding to multipoles 2 ≤ ℓ ≤ 30, the amplitude of the TGSS angular power spectrum is significantly larger than that of the NVSS. We do not identify any observational systematic effects that may explain this mismatch. We have produced a number of physically motivated models for the TGSS angular power spectrum and found that all of them fail to match observations, even when taking into account observational and theoretical uncertainties. The same models provide a good fit to the angular spectrum of the NVSS sources. These results confirm the anomalous nature of the TGSS large-scale power, which has no obvious physical origin and seems to indicate that unknown systematic errors are present in the TGSS dataset.

A Measurement by BOOMERANG of Multiple Peaks in the Angular Power Spectrum of the Cosmic Microwave Background

2002 ◽  
Vol 571 (2) ◽  
pp. 604-614 ◽  
Author(s):  
C. B. Netterfield ◽  
P. A. R. Ade ◽  
J. J. Bock ◽  
J. R. Bond ◽  
J. Borrill ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Multiple Peaks

scholarly journals Planck2018 results

2020 ◽  
Vol 641 ◽  
pp. A3 ◽  
Author(s):  
◽  
N. Aghanim ◽  
Y. Akrami ◽  
M. Ashdown ◽  
J. Aumont ◽  
...  
Keyword(s):  
High Frequency ◽  
Major Change ◽  
Systematic Effect ◽  
Microwave Background ◽  
Extensive Analysis ◽  
Systematic Effects ◽  
Single Detector ◽  
End To End ◽  
Frequency Calibration ◽  
Analogue To Digital

This paper presents the High Frequency Instrument (HFI) data processing procedures for thePlanck2018 release. Major improvements in mapmaking have been achieved since the previousPlanck2015 release, many of which were used and described already in an intermediate paper dedicated to thePlanckpolarized data at low multipoles. These improvements enabled the first significant measurement of the reionization optical depth parameter usingPlanck-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 2015Planckrelease, 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 0.35μK, an accuracy of order 10−4. This is a major legacy from thePlanckHFI 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 10−4level. There is no detectable sign of a residual calibration bias between the first and second acoustic peaks in the CMB channels, at the 10−3level.

scholarly journals 21-cm power spectrum and ionization bias as a probe of long-mode modulated non-Gaussian sky

2019 ◽  
Vol 488 (4) ◽  
pp. 5941-5951
Author(s):  
Shahram Khosravi ◽  
Amirabbas Ghazizadeh ◽  
Shant Baghram
Keyword(s):  
Power Spectrum ◽  
Background Radiation ◽  
Neutral Hydrogen ◽  
Hydrogen Distribution ◽  
Microwave Background ◽  
Power Asymmetry ◽  
Angular Power Spectrum ◽  
Long Wavelength ◽  
Microwave Background Radiation ◽  
Non Gaussian

ABSTRACT The observed hemispherical power asymmetry in cosmic microwave background radiation can be explained by long-wavelength mode (long-mode) modulation. In this paper, we study the possibility of detecting this effect in the angular power spectrum of the 21-cm brightness temperature. For this task, we study the effect of the neutral hydrogen distribution on the angular power spectrum. This is done by formulating the bias parameter of the ionized fraction to the underlying matter distribution. We also discuss the possibility that the long-mode modulation is accompanied by a primordial non-Gaussianity of local type. In this case, we obtain the angular power spectrum with two effects of primordial non-Gaussianity and long-mode modulation. Finally, we show that the primordial non-Gaussianity enhances the long-mode modulated power of the 21-cm signal via the non-Gaussian scale-dependent bias up to four orders of magnitude. Accordingly, observations of the 21-cm signal with upcoming surveys, such as the Square Kilometer Array (SKA), will probably be capable of detecting hemispherical power asymmetry in the context of long-mode modulation.

scholarly journals Stochastic gravitational wave background anisotropies in the mHz band: astrophysical dependencies

2019 ◽  
Vol 493 (1) ◽  
pp. L1-L5
Author(s):  
Giulia Cusin ◽  
Irina Dvorkin ◽  
Cyril Pitrou ◽  
Jean-Philippe Uzan
Keyword(s):  
Black Hole ◽  
Power Spectrum ◽  
Gravitational Wave ◽  
Stellar Evolution ◽  
Strong Dependence ◽  
Angular Power Spectrum ◽  
Orbital Parameters ◽  
Wide Range ◽  
Self Consistent ◽  
Gravitational Wave Background

ABSTRACT We show that the anisotropies of the astrophysical stochastic gravitational wave background in the mHz band have a strong dependence on the modelling of galactic and sub-galactic physics. We explore a wide range of self-consistent astrophysical models for stellar evolution and for the distribution of orbital parameters, all calibrated such that they predict the same number of resolved mergers to fit the number of detections during LIGO/Virgo O1 + O2 observations runs. We show that different physical choices for the process of black hole (BH) collapse and cut-off in the BH mass distribution give fractional differences in the angular power spectrum of anisotropies of up to 50 per cent on all angular scales. We also point out that the astrophysical information which can be extracted from anisotropies is complementary to the isotropic background and individual mergers. These results underline the interest in the anisotropies of the stochastic gravitational wave background as a new and potentially rich field of research, at the cross-road between astrophysics and cosmology.

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