Statistical analysis of catalogs of extragalactic objects. X - Clustering of 4C radio sources

1978 ◽  
Vol 225 ◽  
pp. 7 ◽  
Author(s):  
M. Seldner ◽  
P. J. E. Peebles
Keyword(s):  
Statistical Analysis ◽  
Radio Sources

A NEW ESTIMATE OF THE DENSITY AND INTENSITY OF EXTRAGALACTIC RADIO SOURCES

1963 ◽  
Vol 41 (5) ◽  
pp. 737-741
Author(s):  
G. A. Harrower ◽  
M. J. Watson
Keyword(s):  
Steady State ◽  
Statistical Analysis ◽  
Intensity Factor ◽  
Theoretical Curve ◽  
Radio Sources ◽  
Cosmic Radio ◽  
Factor B ◽  
Steady State Analysis ◽  
Extragalactic Radio Sources ◽  
Best Fit

The recent availability, through a statistical analysis of the Cambridge measurements of cosmic radio sources, of a source-count curve extended to distances at which the effect of recessional velocity is clearly evident in the measurements, has prompted the following comparison of this measured source-count curve with a theoretical curve based on a steady-state analysis. A best fit of measurements and theory allows values of proper density of sources ρ0 and intensity factor b to be estimated independently. The results obtained are ρ0 = 35 × 10−74 sources per cubic meter and b = 11 × 1025 (MKS units).

scholarly journals A Catalogue of Radio Sources Between Declinations ?50° and ?80°

1961 ◽  
Vol 14 (4) ◽  
pp. 497 ◽  
Author(s):  
BY Mills ◽  
OB Slee ◽  
ER Hill
Keyword(s):  
Statistical Analysis ◽  
Radio Telescope ◽  
Small Area ◽  
Radio Sources ◽  
Low Weight ◽  
Cross Type

A catalogue has been prepared of the radio sources observed between declinations -50� and -80�, using the Sydney cross-type radio telescope at a wavelength of 3�5 m; a total of 219 sources is listed. This supplements the earlier catalogues for the declination ranges +10� to -20� and -20� to -50�. In addition to the positions and intensities of the sources, angular sizes of 42 of the strongest sources are given. As before, identifications with bright optical objects have been sought, and a number of possible identifications with emission nebulae and bright galaxies are listed. Because of the small area of sky covered by the present catalogue, the numbers of sources are small (compared with those in our earlier catalogues) so that the statistical analysis of their distribution has comparatively low weight.

scholarly journals Statistical Analysis of Observations of a Complete Sample of Compact Extragalactic Radio Sources

1996 ◽  
Vol 175 ◽  
pp. 97-98
Author(s):  
Y.Y. Kovalev
Keyword(s):  
Statistical Analysis ◽  
Radio Sources ◽  
Statistical Distributions ◽  
Turnover Frequency ◽  
Complete Sample ◽  
Extragalactic Radio Sources ◽  
Bl Lacs

Here are analyzed the results of instantaneous multifrequency observations for a complete sample of 113 extragalactic radio sources (see the paper by Yu.A. Kovalev et al. in these Proceedings) with declinations −30° ÷ 43° from the VLBI–survey. It is tested the hypothesis that quasars and BL Lacs have different nature. Statistical distributions for the turnover flux, turnover frequency, spectral indexes, and other parameters are analyzed.

scholarly journals The Statistical Analysis of Anisotropies

1977 ◽  
Vol 74 ◽  
pp. 75-81
Author(s):  
Adrian Webster
Keyword(s):  
Statistical Analysis ◽  
Statistical Method ◽  
Point Processes ◽  
Radio Sources ◽  
The Many ◽  
Celestial Sphere ◽  
Radio Survey

One of the many uses to which a radio survey may be put is an analysis of the distribution of the radio sources on the celestial sphere to find out whether they are bunched into clusters or lie in preferred regions of space. There are many methods of testing for clustering in point processes and since they are not all equally good this contribution is presented as a brief guide to what seem to be the best of them. The radio sources certainly do not show very strong clustering and may well be entirely unclustered so if a statistical method is to be useful it must be both powerful and flexible. A statistic is powerful in this context if it can efficiently distinguish a weakly clustered distribution of sources from an unclustered one, and it is flexible if it can be applied in a way which avoids mistaking defects in the survey for true peculiarities in the distribution of sources.

scholarly journals Extended Emission in BL Lac Objects

1996 ◽  
Vol 175 ◽  
pp. 53-54
Author(s):  
M. Bondi ◽  
D. Dallacasa ◽  
C. Stanghellini ◽  
R. Della Ceca
Keyword(s):  
Magnetic Field ◽  
Statistical Analysis ◽  
Dynamic Range ◽  
Radio Sources ◽  
Parent Population ◽  
Bl Lac Objects ◽  
Extended Radio ◽  
Bl Lac ◽  
Bl Lacs ◽  
Extended Emission

The study of the extended emission and polarization properties of BL Lacs is an important step for the identification of their parent population. FRI radio sources, the supposed parent population of BL Lacs, have weaker extended radio luminosity and a dominant inferred magnetic field perpendicular to the jet, while FRII radio sources, the supposed parent population of quasars, have stronger extended radio power and an inferred magnetic field parallel to the jet. The only complete sample of radio selected BL Lacs (1 Jy sample, Stickel et al. 1991, ApJ, 374, 431) contains 34 objects. Unfortunately, about half of 1 Jy BL Lacs do not have very high dynamic range images, necessary to detect the low emissivity radio emission surrounding the bright compact source, either because the object was never observed, or because the observation was carried out at the beginning of 1980s with low sensitivity. In 1994 we started a programme using the VLA (A, B, and D configuration, see Table 1) and the WSRT (W in Table 1) to complete the high sensitivity radio imaging of the 1 Jy sample. We aim to investigate morphology and polarization properties, as well as the luminosity of the extended emission. This contribution presents the L band observations. The results are very preliminary, some of the data reduction is still in progress as well as the statistical analysis. The sources in Table 1 have been roughly classified as extended (E), or point-like (P) if no extended feature was detected. Among the 15 sources observed at the highest resolution 13 were classified as extended. In many sources we detect significantly much more extended flux than previously reported from earlier observations. Almost all the BL Lac objects we observed at the highest resolution show some extended features; furthermore, in a few cases, we detected emission on the arcminute scale. The power of the extended luminosity covers 3 orders of magnitude, 3 objects (0537–441, 0820+225, and 2240–260) have values typical of a FRII radio source. These new data will be used for an updated statistical analysis of the properties of the extended emission in the 1 Jy sample of BL Lac objects.

A Preliminary Survey of Radio Sources in a Limited Region of the Sky at a Wavelength of 3·5 m

1957 ◽  
Vol 10 (1) ◽  
pp. 162 ◽  
Author(s):  
BY Mills ◽  
OB Slee
Keyword(s):  
Statistical Analysis ◽  
Major Part ◽  
Significant Degree ◽  
Radio Interferometer ◽  
Radio Sources ◽  
Preliminary Survey ◽  
Instrumental Effects ◽  
Limited Region ◽  
Sample Area ◽  
Celestial Equator

A preliminary catalogue has been prepared of radio sources observed in a sample area of about one steradian near the celestial equator: a total of 383 sources is listed. The brightest nebulae in the area are found to be radio sources. Statistical analysis of the catalogue reveals no obvious cosmological effects except, perhaps, for a significant degree of clustering which may be indicative of metagalactic structure. The catalogue is compared in detail with a recent Cambridge catalogue which includes the sample area; it is found that they are almost completely discordant. A theory is developed which explains this discordance in terms of instrumental effects and it is concluded that a major part of the Cambridge catalogue is affected by the low resolution of their radio interferometer.

Statistical analysis of classification

1966 ◽  
Vol 24 ◽  
pp. 188-189
Author(s):  
T. J. Deeming
Keyword(s):  
Multivariate Analysis ◽  
Statistical Analysis ◽  
Classification Scheme ◽  
Analytical Procedure ◽  
Narrow Band ◽  
Scientific Research ◽  
Maximum Amount ◽  
Amount Of Information

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.

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