scholarly journals Sensitivity of neutrinos to the supernova turbulence power spectrum: Point source statistics

2015 ◽  
Vol 92 (1) ◽  
Author(s):  
James P. Kneller ◽  
Neel V. Kabadi
Keyword(s):  
Power Spectrum ◽  
Point Source ◽  
Spectrum Point

scholarly journals Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array

2019 ◽  
Vol 36 ◽  
Author(s):  
Cathryn M. Trott ◽  
Catherine A. Watkinson ◽  
Christopher H. Jordan ◽  
Shintaro Yoshiura ◽  
Suman Majumdar ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Point Source ◽  
Noise Level ◽  
Future Prospects ◽  
Careful Choice ◽  
Murchison Widefield Array ◽  
Using Data ◽  
Redundant Arrays ◽  
High Band ◽  
Compact Array

AbstractWe apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv-plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167–197 MHz; z = 6.2–7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.

scholarly journals The power spectrum of the Point Source Catalogue redshift survey

1999 ◽  
Vol 308 (2) ◽  
pp. 289-301 ◽  
Author(s):  
W. Sutherland ◽  
H. Tadros ◽  
G. Efstathiou ◽  
C. S. Frenk ◽  
O. Keeble ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Point Source ◽  
Redshift Survey

scholarly journals The angular power spectrum measurement of the Galactic synchrotron emission using the TGSS survey

2017 ◽  
Vol 12 (S333) ◽  
pp. 157-161
Author(s):  
Samir Choudhuri ◽  
Somnath Bharadwaj ◽  
Sk. Saiyad Ali ◽  
Nirupam Roy ◽  
H. T. Intema ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Power Spectrum ◽  
Point Source ◽  
Power Law ◽  
Point Sources ◽  
Synchrotron Emission ◽  
Angular Power Spectrum ◽  
Spectrum Measurement ◽  
Upper Limit ◽  
Sky Survey

AbstractCharacterizing the diffuse Galactic synchrotron emission (DGSE) at arcminute angular scales is needed to remove this foregrounds in cosmological 21-cm measurements. Here, we present the angular power spectrum (Cℓ) measurement of the diffuse Galactic synchrotron emission using two fields observed by the TIFR GMRT Sky Survey (TGSS). We apply 2D Tapered Gridded Estimator (TGE) to estimate the Cℓ from the visibilities. We find that the residual data after subtracting the point sources is likely dominated by the diffuse Galactic synchrotron radiation across the angular multipole range 240 ≤ ℓ ≲ 500. We fit a power law to the measured Cℓ over this ℓ range. We find that the slopes in both fields are consistent with earlier measurements. For the second field, however, we interpret the measured Cℓ as an upper limit for the DGSE as there is an indication of a significant residual point source contribution.

Evolution of the angular power spectrum of scattered radiation from a point source upon propagation in a turbid medium

2004 ◽  
Vol 96 (5) ◽  
pp. 804-809 ◽  
Author(s):  
V. G. Gavrilenko ◽  
A. V. Sorokin ◽  
G. V. Jandieri ◽  
V. G. Jandieri
Keyword(s):  
Power Spectrum ◽  
Point Source ◽  
Scattered Radiation ◽  
Turbid Medium ◽  
Angular Power Spectrum

scholarly journals The CMB angular power spectrum via component separation: a study on Planck data

2019 ◽  
Vol 624 ◽  
pp. A67
Author(s):  
C. Umiltà ◽  
J. F. Cardoso ◽  
K. Benabed ◽  
M. Le Jeune
Keyword(s):  
Power Spectrum ◽  
Point Source ◽  
Cosmological Parameters ◽  
Point Sources ◽  
Blind Separation ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Planck Data ◽  
Small Scales ◽  
Source Emission

Aims. We investigate the extent to which foreground-cleaned cosmic microwave background (CMB) maps can be used to estimate cosmological parameters at small scales. Methods. We use the SMICA method, a blind separation technique that works directly at the spectral level. In this work we focus on the small scales of the CMB angular power spectrum, which are chiefly affected by noise and extragalactic foregrounds, such as point sources. We adapt SMICA to use only cross-spectra between data maps, thus avoiding the noise bias. In this study, performed using both simulations and Planck 2015 data, we fit for extragalactic point sources by modelling them as shot noise of two independent populations. Results. In simulations, we correctly recover the point-source emission law, and obtain a CMB angular power spectrum that has an average foreground residual of one fifth of the CMB power at ℓ ≥ 2200. With Planck data, the recovered point-source emission law corresponds to external estimates, with some offsets at the highest and lowest frequencies, possibly due to frequency decoherence of point sources. The CMB angular power spectrum residuals are consistent with what we find in simulations. The cosmological parameters obtained from the simulations and the data show offsets up to 1σ on average from their expected values. Biases on cosmological parameters in simulations represent the expected level of bias in Planck data. Conclusions. The results on cosmological parameters depend on the detail of the foreground residual contamination in the spectrum, and therefore a tailored modelling of the likelihood foreground model is required.

ON THE LINEAR FILTERS FOR POINT SOURCE EXTRACTION OF THE PLANCK MISSION

2005 ◽  
Vol 14 (07) ◽  
pp. 1251-1272
Author(s):  
LUNG-YIH CHIANG ◽  
PAVEL D. NASELSKY ◽  
IGOR D. NOVIKOV
Keyword(s):  
Power Spectrum ◽  
Point Source ◽  
A Priori ◽  
Point Sources ◽  
Noise Power ◽  
Linear Filters ◽  
Angular Power Spectrum ◽  
Beam Shape ◽  
Compact Source ◽  
Source Extraction

The manifestation of point sources in the upcoming Planck maps is a direct reflection of the properties of the pixelized antenna beam shape for each frequency, which is related to the scan strategy, pointing accuracy, noise properties and map-making algorithm. In this paper we firstly compare analytically two filters for the Planck point source extraction, namely, the adaptive top-hat filter (ATHF) and the theoretically-optimal filter (TOF). Our analyses are based on the premise that the required experiment parameters of the TOF are assumed to be already known: the CMB and noise power spectrum and a circular Gaussian beam shape and size. Whereas, the ATHF does not need any a priori knowledge. The analyses show that the TOF is optimal in terms of the gain after the parameter inputs. We simulate the Planck HFI 100 GHz channel with elliptical beam in rotation to test the efficiency of the TOF and the ATHF. We also apply the ATHF on the WMAP Q-band map and the derived map (the foreground-cleaned map by Tegmark, de Oliveira Costa & Hamilton) from the WMAP one-year data. The uncertainties on the angular power spectrum will hamper the efficiency of the TOF. The ATHF is computationally efficient in tackling more realistic data such as the following effects: an elliptical beam with slow precession and the change of the beam ellipticity ratio due to possible mirror degradation. The ATHF is well suited for the construction of the Planck Early Release Compact Source Catalogue.

The on-line use of histogram data for high-speed correction and alignment of electron microscope images

1984 ◽  
Vol 42 ◽  
pp. 556-557
Author(s):  
William Krakow
Keyword(s):  
Power Spectrum ◽  
High Speed ◽  
Direct Memory Access ◽  
Digital Television ◽  
Contrast Transfer Function ◽  
The Past ◽  
High Resolution Tem ◽  
On Line ◽  
Correction Of Astigmatism ◽  
The Fourier Transform

In the past few years on-line digital television frame store devices coupled to computers have been employed to attempt to measure the microscope parameters of defocus and astigmatism. The ultimate goal of such tasks is to fully adjust the operating parameters of the microscope and obtain an optimum image for viewing in terms of its information content. The initial approach to this problem, for high resolution TEM imaging, was to obtain the power spectrum from the Fourier transform of an image, find the contrast transfer function oscillation maxima, and subsequently correct the image. This technique requires a fast computer, a direct memory access device and even an array processor to accomplish these tasks on limited size arrays in a few seconds per image. It is not clear that the power spectrum could be used for more than defocus correction since the correction of astigmatism is a formidable problem of pattern recognition.

Log-log scale roughness spectroscopy of surfaces

1993 ◽  
Vol 51 ◽  
pp. 224-225
Author(s):  
P. Fraundorf ◽  
B. Armbruster
Keyword(s):  
Power Spectrum ◽  
Autocorrelation Function ◽  
Power Spectra ◽  
Scanning Force Microscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Scanning Force ◽  
Lateral Structure ◽  
Scale Roughness

Optical interferometry, confocal light microscopy, stereopair scanning electron microscopy, scanning tunneling microscopy, and scanning force microscopy, can produce topographic images of surfaces on size scales reaching from centimeters to Angstroms. Second moment (height variance) statistics of surface topography can be very helpful in quantifying “visually suggested” differences from one surface to the next. The two most common methods for displaying this information are the Fourier power spectrum and its direct space transform, the autocorrelation function or interferogram. Unfortunately, for a surface exhibiting lateral structure over several orders of magnitude in size, both the power spectrum and the autocorrelation function will find most of the information they contain pressed into the plot’s origin. This suggests that we plot power in units of LOG(frequency)≡-LOG(period), but rather than add this logarithmic constraint as another element of abstraction to the analysis of power spectra, we further recommend a shift in paradigm.

XRMF applications of a monolithic, polycapillary, focusing x-ray optic

1996 ◽  
Vol 54 ◽  
pp. 240-241
Author(s):  
D. A. Carpenter ◽  
Ning Gao ◽  
G. J. Havrilla
Keyword(s):  
Trace Elements ◽  
Point Source ◽  
Focal Spot ◽  
Fluorescence Analysis ◽  
X Rays ◽  
Focal Distance ◽  
Spot Diameter ◽  
X Ray ◽  
Focal Spot Diameter

A monolithic, polycapillary, x-ray optic was adapted to a laboratory-based x-ray microprobe to evaluate the potential of the optic for x-ray micro fluorescence analysis. The polycapillary was capable of collecting x-rays over a 6 degree angle from a point source and focusing them to a spot approximately 40 µm diameter. The high intensities expected from this capillary should be useful for determining and mapping minor to trace elements in materials. Fig. 1 shows a sketch of the capillary with important dimensions.The microprobe had previously been used with straight and with tapered monocapillaries. Alignment of the monocapillaries with the focal spot was accomplished by electromagnetically scanning the focal spot over the beveled anode. With the polycapillary it was also necessary to manually adjust the distance between the focal spot and the polycapillary.The focal distance and focal spot diameter of the polycapillary were determined from a series of edge scans.

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