scholarly journals All-sky angular power spectrum – I. Estimating brightness temperature fluctuations using the 150-MHz TGSS survey

2020 ◽  
Vol 494 (2) ◽  
pp. 1936-1945 ◽  
Author(s):  
Samir Choudhuri ◽  
Abhik Ghosh ◽  
Nirupam Roy ◽  
Somnath Bharadwaj ◽  
Huib T Intema ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Galactic Plane ◽  
Cosmic Ray ◽  
Point Sources ◽  
Synchrotron Emission ◽  
Angular Power Spectrum ◽  
Latitude Range ◽  
Diffuse Halo ◽  
Sky Survey ◽  
Before And After

ABSTRACT Measurements of the Galactic synchrotron emission are important for the 21-cm studies of the epoch of reionization. The study of synchrotron emission is also useful for quantifying the fluctuations in the magnetic field and the cosmic-ray electron density of the turbulent interstellar medium (ISM) of our Galaxy. Here, we present the all-sky angular power spectrum (Cℓ) measurements of the diffuse synchrotron emission obtained using the TIFR GMRT Sky Survey (TGSS) at 150 MHz. We estimate Cℓ using visibility data both before and after subtracting the modelled point sources. The amplitude of the measured Cℓ decreases significantly after subtracting the point sources, and it is slightly higher in the Galactic plane for the residual data. The residual Cℓ is most likely to be dominated by the Galactic synchrotron emission. The amplitude of the residual Cℓ decreases significantly away from the Galactic plane. We find that the measurements are quite symmetric in the Northern and Southern hemispheres except in the latitude range 15°−30°, which is the transition region from the disc-dominated to the diffuse halo-dominated region. A comparison between this interferometric measurement and the scaled version of the Haslam rms map at 150 MHz shows that the correlation coefficient (r) is greater than 0.5 for most of the latitude ranges considered here. This indicates that the TGSS is quite sensitive to the diffuse Galactic synchrotron radiation.

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.

scholarly journals The Angular Power Spectrum of Galaxies from Early Sloan Digital Sky Survey Data

2002 ◽  
Vol 571 (1) ◽  
pp. 191-205 ◽  
Author(s):  
Max Tegmark ◽  
Scott Dodelson ◽  
Daniel J. Eisenstein ◽  
Vijay Narayanan ◽  
Roman Scoccimarro ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Survey Data ◽  
Sloan Digital Sky Survey ◽  
Angular Power Spectrum ◽  
Sky Survey

Angular power spectrum estimation of cosmic ray anisotropies with full or partial sky coverage

2004 ◽  
Vol 2004 (10) ◽  
pp. 008-008 ◽  
Author(s):  
O Deligny ◽  
E Armengaud ◽  
T Beau ◽  
P Da Silva ◽  
J-Ch Hamilton ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cosmic Ray ◽  
Spectrum Estimation ◽  
Angular Power Spectrum ◽  
Power Spectrum Estimation

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.

scholarly journals The Sloan Digital Sky Survey Data Release 7 galaxy angular power spectrum

2012 ◽  
Vol 421 (3) ◽  
pp. 2043-2053 ◽  
Author(s):  
Brett Hayes ◽  
Robert Brunner ◽  
Ashley Ross
Keyword(s):  
Power Spectrum ◽  
Survey Data ◽  
Sloan Digital Sky Survey ◽  
Angular Power Spectrum ◽  
Sky Survey ◽  
Data Release

Changes in the cosmic-ray power spectrum during solar flares

1991 ◽  
Vol 69 (8-9) ◽  
pp. 976-980
Author(s):  
K. Kudela ◽  
A. G. Ananth ◽  
D. Venkatesan
Keyword(s):  
Power Spectrum ◽  
Solar Flares ◽  
Cosmic Ray ◽  
Ground Level ◽  
Frequency Interval ◽  
Spectral Form ◽  
High Energies ◽  
Power Spectral ◽  
Before And After ◽  
Monitor Data

The power spectrum analyses of cosmic-ray neutron-monitor data at two different cutoff rigidity stations, Calgary (1.09 GV) and Lomnicky Stit (4.0 GV), exhibit similar changes in power spectral form in the frequency interval 10−5–10−3 Hz before and after the six solar flare events that occurred from January 1989 to June 1990. The power spectrum index n at both stations, which showed significantly lower values one day before the flare onset, indicated a sharp steepening of the spectral shape following the flare event. The change in the power spectrum is attributed to the redistribution of inhomogeneities near the sun, produced before the solar flares in which cosmic-ray particles are accelerated to high energies, to produce a ground level event.

scholarly journals Hoinga: a supernova remnant discovered in the SRG/eROSITA All-Sky Survey eRASS1

2021 ◽  
Vol 648 ◽  
pp. A30
Author(s):  
W. Becker ◽  
N. Hurley-Walker ◽  
Ch. Weinberger ◽  
L. Nicastro ◽  
M. G. F. Mayer ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Galactic Plane ◽  
Point Sources ◽  
Galactic Latitude ◽  
Gas Temperature ◽  
High Galactic Latitude ◽  
X Ray ◽  
Flux Limit ◽  
Sky Survey ◽  
The Universe

Supernova remnants (SNRs) are observable for about (6−15) × 104 yr before they fade into the Galactic interstellar medium. With a Galactic supernova rate of approximately two per century, we can expect to have of the order of 1200 SNRs in our Galaxy. However, only about 300 of them are known to date, with the majority having been discovered in Galactic plane radio surveys. Given that these SNRs represent the brightest tail of the distribution and are mostly located close to the plane, they are not representative of the complete sample. The launch of the Russian-German observatory SRG/eROSITA in July 2019 brought a promising new opportunity to explore the Universe. Here we report findings from the search for new SNRs in the eROSITA all-sky survey data which led to the detection of one of the largest SNRs discovered at wavelengths other than the radio: G249.5+24.5. This source is located at a relatively high Galactic latitude, where SNRs are not usually expected to be found. The remnant, ‘Hoinga’, has a diameter of about 4. °4 and shows a circular shaped morphology with diffuse X-ray emission filling almost the entire remnant. Spectral analysis of the remnant emission reveals that an APEC spectrum from collisionally ionised diffuse gas and a plane-parallel shock plasma model with non-equilibrium ionisation are both able to provide an adequate description of the data, suggesting a gas temperature of the order of kT = 0.1−0.02+0.02 keV and an absorbing column density of NH = 3.6−0.6+0.7 × 1020 cm−2. Various X-ray point sources are found to be located within the remnant boundary but none seem to be associated with the remnant itself. Subsequent searches for a radio counterpart of the Hoinga remnant identified its radio emission in archival data from the Continuum HI Parkes All-Sky Survey and the 408-MHz ‘Haslam’ all-sky survey. The radio spectral index α = −0.69 ± 0.08 obtained from these data definitely confirms the SNR nature of Hoinga. We also analysed INTEGRAL SPI data for fingerprints of 44Ti emission, which is an ideal candidate with which to study nucleosynthesis imprinting in young SNRs. Although no 44Ti emission from Hoinga was detected, we were able to set a 3σ upper flux limit of 9.2 × 10−5 ph cm−2 s−1. From its size and X-ray and radio spectral properties we conclude that Hoinga is a middle-aged Vela-like SNR located at a distance of about twice that of the Vela SNR, i.e. at ~500 pc.

scholarly journals Estimating the large-scale angular power spectrum in the presence of systematics: a case study of Sloan Digital Sky Survey quasars

2013 ◽  
Vol 435 (3) ◽  
pp. 1857-1873 ◽  
Author(s):  
Boris Leistedt ◽  
Hiranya V. Peiris ◽  
Daniel J. Mortlock ◽  
Aurélien Benoit-Lévy ◽  
Andrew Pontzen
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Sloan Digital Sky Survey ◽  
Angular Power Spectrum ◽  
Sky Survey
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