scholarly journals Application of Mathematical Theories of Approximation to Aerial Smoothing in Radio Astronomy

1957 ◽  
Vol 10 (1) ◽  
pp. 16 ◽  
Author(s):  
J Arsac
Keyword(s):  
Systematic Error ◽  
Finite Length ◽  
Radio Astronomy ◽  
Brightness Distribution ◽  
Radio Brightness ◽  
Object Function ◽  
Trigonometric Sum ◽  
Radio Brightness Distribution ◽  
Image Function ◽  
The Difference

An aerial rarely provides a perfect image of a radio brightness distribution. If we consider an array as a filter of "spatial harmonics", the image function is a trigonometric sum approximating the object function. An application of mathematical theories shows the influence of the length and the shape of the array on the difference between object and image. Whatever the array, the image contrasts are bounded. The results provided by various arrays of the same length may be reduced by linear transforms. Inaccuracies of measurement, especially those due to the receiver noise, add to the systematic error due to the finite length of the antenna. We may try to get a compromise between these various causes of uncertainty.

scholarly journals The Radio Brightness Distribution on the Sun at 21 cm from Combined Eclipse and Pencil?Beam Observations

1961 ◽  
Vol 14 (3) ◽  
pp. 403 ◽  
Author(s):  
T Krishnan ◽  
NR Labrum
Keyword(s):  
High Resolution ◽  
High Sensitivity ◽  
Brightness Distribution ◽  
Pencil Beam ◽  
The Sun ◽  
Radio Brightness ◽  
Radio Brightness Distribution ◽  
Grating Interferometer

A study of the brightness distribution on the Sun at 21-cm wavelength on April 8, 1959, is described. High resolution observations were made of the partial eclipse on that day with a simple radiometer of high sensitivity. The brightness distribution of the uneclipsed Sun at the same wavelength was obtained using a cross-grating interferometer, which enabled the bright regions to be located accurately.

Techniques for Decimetre Wavelength Observations of Radio Plages and Bursts

1967 ◽  
Vol 1 (2) ◽  
pp. 55-55
Author(s):  
W. N. Christiansen
Keyword(s):  
Brightness Distribution ◽  
Resolving Power ◽  
The Sun ◽  
Two Dimensional ◽  
Radio Brightness ◽  
Field Station ◽  
Radio Brightness Distribution ◽  
The University

The first daily maps showing the two-dimensional radio brightness distribution over the Sun were produced at Fleurs ten years ago when the 64-antenna grating cross was completed. The maps had a resolution of 3′ arc at λ = 21 cm.When the Fleurs field station was given to the University by CSIRO in 1963 it was decided to use the antennas of the grating cross and add to them four or more larger antennas (45 ft diameter) to produce a pair of high resolving-power compound interferometers.

scholarly journals Vlbi Observations of the Compact Components in M82

1986 ◽  
Vol 7 ◽  
pp. 661-663
Author(s):  
N. Bartel ◽  
M.I. Ratner ◽  
A.E.E. Rogers ◽  
I.I. Shapiro ◽  
R.J. Bonometti ◽  
...  
Keyword(s):  
Central Region ◽  
Brightness Distribution ◽  
Radio Brightness ◽  
Upper Limit ◽  
Vlbi Observations ◽  
Radio Brightness Distribution ◽  
The Galaxy ◽  
Considerable Detail

The nearby IrrII galaxy M82 (3C 231, NGC3034) is known to have a complex, very elongated radio brightness distribution in the central region of the galaxy (e.g., Kronberg and Wilkinson 1975). Because of the galaxy’s proximity (distance ~ 3.3 Mpc; Tammann and Sandage 1968), the brightness distribution can be investigated in considerable detail. Recently Unger et al. (1984) and Kronberg, Biermann, and Schwab (1985; see also Kronberg 1986) distinguished about 20 compact components in the central region, most of them unresolved with an upper limit on their angular sizes of ~ 150 mas corresponding to an upper limit on their linear sizes of ~ 2 pc. About half of the components were observed at more than one frequency and at several epochs and were found typically to have steep spectra between 5 and 15 GHz and (Kronberg and Sramek 1985) slowly decreasing flux densities.

scholarly journals Large-Scale Radio Jets

1983 ◽  
Vol 6 ◽  
pp. 731-733
Author(s):  
R.A. Laing
Keyword(s):  
Surface Brightness ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Radio Galaxies ◽  
Brightness Distribution ◽  
Physical Parameters ◽  
Radio Brightness ◽  
Radio Jets ◽  
Radio Brightness Distribution

The purpose of this review is to outline the systematic properties of radio jets on kpc scales, as derived from the basic observations of surface brightness and linear polarization and to emphasize the uncertainties in the determination of their physical parameters. These results come primarily from observations of about 100 jets with the VLA: a fuller account is given by Bridle (1982) and the proceedings of IAU Symposium 97 contain many illustrations and references, which must be omitted here.I take a “jet” to be a feature in the radio brightness distribution which is at least four times as long as it is wide, which can be clearly separated (spatially or by brightness contrast) from the rest of the source and points away from a radio core. Wilson (1982) has considered jets in spiral galaxies and I shall discuss only the more luminous jets found in elliptical radio galaxies and quasars.

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