scholarly journals The XFaster Power Spectrum and Likelihood Estimator for the Analysis of Cosmic Microwave Background Maps

2021 ◽  
Vol 922 (2) ◽  
pp. 132
Author(s):  
A. E. Gambrel ◽  
A. S. Rahlin ◽  
X. Song ◽  
C. R. Contaldi ◽  
P. A. R. Ade ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Power Spectrum ◽  
Transfer Functions ◽  
Data Sets ◽  
Microwave Background ◽  
Data Set ◽  
Angular Power Spectrum ◽  
Quadratic Estimator ◽  
Diagonal Approximation ◽  
Analysis Package

Abstract We present the XFaster analysis package, a fast, iterative angular power spectrum estimator based on a diagonal approximation to the quadratic Fisher matrix estimator. It uses Monte Carlo simulations to compute noise biases and filter transfer functions and is thus a hybrid of both Monte Carlo and quadratic estimator methods. In contrast to conventional pseudo-C ℓ –based methods, the algorithm described here requires a minimal number of simulations and does not require them to be precisely representative of the data to estimate accurate covariance matrices for the bandpowers. The formalism works with polarization-sensitive observations and also data sets with identical, partially overlapping, or independent survey regions. The method was first implemented for the analysis of BOOMERanG data and also used as part of the Planck analysis. Here we describe the full, publicly available analysis package, written in Python, as developed for the analysis of data from the 2015 flight of the Spider instrument. The package includes extensions for self-consistently estimating null spectra and estimating fits for Galactic foreground contributions. We show results from the extensive validation of XFaster using simulations and its application to the Spider data set.

scholarly journals Observations of the CMB on Scales of 2° to 15°

1999 ◽  
Vol 183 ◽  
pp. 103-103 ◽  
Author(s):  
R.D. Davies ◽  
R.J. Davis ◽  
A. Wilkinson ◽  
R.A. Watson ◽  
S.J. Melhuish ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Data Sets ◽  
Two Dimensional ◽  
Microwave Background ◽  
Data Set ◽  
Galactic Emission ◽  
Likelihood Analysis ◽  
Fluctuation Amplitude ◽  
Intrinsic Fluctuation

Beamswitching has been used at 10, 15 and 33 GHz to map the microwave background over the Declination range 30° to 45°, covering more than one steradian of the sky. The beamwidth is 5° and the beam-throw is ±8° at each frequency. The three data sets are used to separate Galactic emission from intrinsic CMB emission. For the scan at Dec = 40° the intrinsic fluctuation level is ΔTrms = 48+21−15 μK on a coherence scale of 4°; the equivalent analysis for a Harrison-Zeldovich model gives a power spectrum normalisation of Qrms = 22+10−6 μK. The value of the fluctuation amplitude calculated from the likelihood analysis of the two-dimensional data set is ΔTrms = 54 ± 13 μK at 10 GHz and 39+8−7 μK at 15 GHz.

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 CNVScope: Visually Exploring Copy Number Aberrations in Cancer Genomes

2019 ◽  
Vol 18 ◽  
pp. 117693511989029
Author(s):  
James LT Dalgleish ◽  
Yonghong Wang ◽  
Jack Zhu ◽  
Paul S Meltzer
Keyword(s):  
Copy Number ◽  
High Performance ◽  
Data Sets ◽  
Data Set ◽  
The Public ◽  
Public Data ◽  
Analysis Package ◽  
Cis And Trans ◽  
High Performance Computing Cluster ◽  
Shiny Application

Motivation: DNA copy number (CN) data are a fast-growing source of information used in basic and translational cancer research. Most CN segmentation data are presented without regard to the relationship between chromosomal regions. We offer both a toolkit to help scientists without programming experience visually explore the CN interactome and a package that constructs CN interactomes from publicly available data sets. Results: The CNVScope visualization, based on a publicly available neuroblastoma CN data set, clearly displays a distinct CN interaction in the region of the MYCN, a canonical frequent amplicon target in this cancer. Exploration of the data rapidly identified cis and trans events, including a strong anticorrelation between 11q loss and17q gain with the region of 11q loss bounded by the cell cycle regulator CCND1. Availability: The shiny application is readily available for use at http://cnvscope.nci.nih.gov/ , and the package can be downloaded from CRAN ( https://cran.r-project.org/package=CNVScope ), where help pages and vignettes are located. A newer version is available on the GitHub site ( https://github.com/jamesdalg/CNVScope/ ), which features an animated tutorial. The CNVScope package can be locally installed using instructions on the GitHub site for Windows and Macintosh systems. This CN analysis package also runs on a linux high-performance computing cluster, with options for multinode and multiprocessor analysis of CN variant data. The shiny application can be started using a single command (which will automatically install the public data package).

scholarly journals A New Robust Diagnostic Plot for Classifying Good and Bad High Leverage Points in a Multiple Linear Regression Model

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Mohammed Alguraibawi ◽  
Habshah Midi ◽  
A. H. M. Rahmatullah Imon
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Multiple Linear Regression Model ◽  
Parameter Estimates ◽  
Data Sets ◽  
Data Set ◽  
Monte Carlo Simulation Study ◽  
Leverage Points ◽  
Diagnostic Plot ◽  
Leverage Point

Identification of high leverage point is crucial because it is responsible for inaccurate prediction and invalid inferential statement as it has a larger impact on the computed values of various estimates. It is essential to classify the high leverage points into good and bad leverage points because only the bad leverage points have an undue effect on the parameter estimates. It is now evident that when a group of high leverage points is present in a data set, the existing robust diagnostic plot fails to classify them correctly. This problem is due to the masking and swamping effects. In this paper, we propose a new robust diagnostic plot to correctly classify the good and bad leverage points by reducing both masking and swamping effects. The formulation of the proposed plot is based on the Modified Generalized Studentized Residuals. We investigate the performance of our proposed method by employing a Monte Carlo simulation study and some well-known data sets. The results indicate that the proposed method is able to improve the rate of detection of bad leverage points and also to reduce swamping and masking effects.

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 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.

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