The Spectral Index Distribution of Cygnus A

1982 ◽  
pp. 29-31
Author(s):  
P. F. Scott
Keyword(s):  
Spectral Index ◽  
Cygnus A ◽  
Index Distribution

scholarly journals The Spectral Index Distribution of Cygnus A

1982 ◽  
Vol 97 ◽  
pp. 29-31
Author(s):  
P. F. Scott
Keyword(s):  
Magnetic Field ◽  
Spectral Index ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Cygnus A ◽  
Index Distribution ◽  
High Dynamic ◽  
5 Ghz

High dynamic range maps of Cygnus A at 2.7 and 5 GHz have been used to investigate the variation of spectral index over the extended parts of the source. Although both components show a steepening of spectral index away from the hotspots there is a marked asymmetry between the two components. This is interpreted as being due to a higher value of magnetic field in the Sf component.

scholarly journals Aperture Synthesis Observations of Cygnus A at 86.2 Ghz

1982 ◽  
Vol 97 ◽  
pp. 27-28
Author(s):  
M. Birkinshaw ◽  
M.C.H. Wright
Keyword(s):  
Spectral Index ◽  
Aperture Synthesis ◽  
Central Component ◽  
Cygnus A

Recent observations of Cygnus A with the Hat Creek interferometer at 86.2 GHz limit the spectral curvature of the hotspots and show that the diffuse lobe emission has a spectral index of about 1.5. The central component is, at most, weakly variable and its spectrum shows a distinct break to a spectral index near 0.65 at about 20 GHz.

scholarly journals The large-scale radio spectral index distribution of Centaurus A

1997 ◽  
Vol 121 (1) ◽  
pp. 11-11 ◽  
Author(s):  
J. A. Combi ◽  
G. E. Romero
Keyword(s):  
Spectral Index ◽  
Large Scale ◽  
Index Distribution ◽  
Centaurus A

Investigation of cubic non-linearity-driven electrostatic structures in the presence of double spectral index distribution function

2019 ◽  
Vol 60 (1) ◽  
pp. e201900065 ◽  
Author(s):  
M.N.S. Qureshi ◽  
K.H. Shah ◽  
Jiankui Shi ◽  
W. Masood ◽  
H.A. Shah
Keyword(s):  
Distribution Function ◽  
Spectral Index ◽  
Index Distribution

scholarly journals A multi-frequency study of the spectral index distribution in the SNR CTB 80

2005 ◽  
Vol 440 (1) ◽  
pp. 171-177 ◽  
Author(s):  
G. Castelletti ◽  
G. Dubner
Keyword(s):  
Spectral Index ◽  
Index Distribution

scholarly journals Measurements of Interstellar Scattering in the Cygnus Region

1988 ◽  
Vol 129 ◽  
pp. 303-304
Author(s):  
S. Spangler ◽  
A. Fey ◽  
R. Mutel
Keyword(s):  
Radio Source ◽  
Spectral Index ◽  
High Quality ◽  
Visibility Function ◽  
Cygnus A ◽  
Interstellar Scattering

We report progress on a study of interstellar scattering in the direction of the constellation Cygnus. A high quality, 1663 MHz VLBI image has been obtained of the radio source 2013+370, whose structure at this frequency is dominated by scattering. The visibility function indicates that the spectral index of the interstellar density irregularities is between 3.7 and 4.0, with the higher value being somewhat more likely. Another project consists of multifrequency observations of eight sources in this region. Pronounced changes in the scattering are observed for sources separated by only a few degrees.

scholarly journals CHANG-ES

2019 ◽  
Vol 632 ◽  
pp. A12 ◽  
Author(s):  
Philip Schmidt ◽  
Marita Krause ◽  
Volker Heesen ◽  
Aritra Basu ◽  
Rainer Beck ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spectral Index ◽  
Time Scales ◽  
Thermal Emission ◽  
Cosmic Ray ◽  
Wide Band ◽  
Radial Dependence ◽  
Very Large Array ◽  
Star Forming ◽  
Index Distribution

Context. Cosmic-ray electrons (CREs) originating from the star-forming discs of spiral galaxies frequently form extended radio haloes that are best observable in edge-on galaxies, where their properties can be directly investigated as a function of vertical height above the disc. Aims. For the present study, we selected two nearby edge-on galaxies from the Continuum Halos in Nearby Galaxies – an EVLA Survey (CHANG-ES), NGC 891 and 4565, which differ largely in their detectable halo extent and their star-formation rates (SFRs). Our aim is to figure out how such differences are related to the (advective and/or diffusive) CRE transport in the disc and in the halo. Methods. We use wide-band 1.5 and 6 GHz Very Large Array (VLA) observations obtained in the B, C, and D configurations, and combine the 6 GHz images with Effelsberg observations to correct for missing short spacings. After subtraction of the thermal emission, we investigate the spatially resolved synchrotron spectral index distribution in terms of CRE spectral ageing. We further compute total magnetic field strengths assuming equipartition between the cosmic-ray (CR) energy density and the magnetic field, and measure synchrotron scale heights at both frequencies. Based on the fitted vertical profiles of the synchrotron intensity and on the spectral index profile between 1.5 and 6 GHz, we create purely advective and purely diffusive CRE transport models by numerically solving the 1D diffusion–loss equation. In particular, we investigate for the first time the radial dependence of synchrotron and magnetic field scale heights, advection speeds, and diffusion coefficients, whereas previous studies of these two galaxies only determined global values of these quantities. Results. We find that the overall spectral index distribution of NGC 891 is mostly consistent with continuous CRE injection. In NGC 4565, many of the local synchrotron spectra (even in the disc) feature a break between 1.5 and 6 GHz and are thus more in line with discrete-epoch CRE injection (Jaffe–Perola (JP) or Kardashev–Pacholczyk (KP) models). This implies that CRE injection time-scales are lower than the synchrotron cooling time-scales. The synchrotron scale height of NGC 891 increases with radius, indicating that synchrotron losses are significant. NGC 891 is probably dominated by advective CRE transport at a velocity of ≳150 km s−1. In contrast, NGC 4565 is diffusion-dominated up to z = 1 kpc or higher, with a diffusion coefficient of ≥2 × 1028 cm2 s−1.

scholarly journals The pulsar spectral index distribution

2013 ◽  
Vol 431 (2) ◽  
pp. 1352-1358 ◽  
Author(s):  
S. D. Bates ◽  
D. R. Lorimer ◽  
J. P. W. Verbiest
Keyword(s):  
Spectral Index ◽  
Index Distribution
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