scholarly journals The optical identification of radio sources

1959 ◽  
Vol 9 ◽  
pp. 507-513
Author(s):  
D. W. Dewhirst
Keyword(s):  
Radio Sources ◽  
Astronomy Observatory ◽  
National Geographic Society ◽  
Optical Identification ◽  
National Geographic ◽  
Extensive Search ◽  
Sky Survey ◽  
A Minor ◽  
Minor Character

Previous attempts to identify any large proportion of the discrete sources discovered at meter wavelengths have met with small success. In the investigation briefly reported here an extensive search has been made on the original plates of the 48-inch Palomar—National Geographic Society Sky Survey, using the available published radio data, but more especially the as yet unpublished results of a survey between +50 and −10 degrees declination that has been made with the interferometer of the Mullard Radio Astronomy Observatory, Cambridge. This radio survey (3C) has been carried out at 159.5 Mc/s using the aerial array of the 2C survey [1] in modified form. An account of the observation and reduction of this recent survey is given by other speakers in the Symposium. The area of sky covered by the 3C survey, and the criteria for the selection and classification of the sources, are likely to undergo small extensions and modifications before the final catalog is ready for publication, but these modifications will be of a minor character and will not alter the general conclusions of the present paper.

scholarly journals General Superclustering

1983 ◽  
Vol 6 ◽  
pp. 753-756
Author(s):  
G.O. Abell
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Statistical Approach ◽  
Clusters Of Galaxies ◽  
National Geographic Society ◽  
National Geographic ◽  
Large Numbers ◽  
Sky Survey ◽  
Point Correlation ◽  
Point Correlation Function

The distribution of rich clusters of galaxies revealed on the photographs taken for the National Geographic Society-Palomar Observatory Sky Survey shows a strong dumpiness on a scale of 100 Mpc (for H = 50 km s–1 Mpc–1), with vast intraclump regions apparently void of rich clusters (Abell 1958; 1961). Studies of the n-point correlation function by Peebles and his associates (e.g., Peebles 1980 and references therein) show that this large-scale dumpiness applies also to individual galaxies. Peebles’ statistical approach does not, of course, indicate individual superclusters or their structures; that kind of information awaited the breakthrough provided by the development of high-speed detectors, with which radial velocities of large numbers of galaxies can be obtained in reasonable observing times.

QSQs and Radio Galaxies - their Spectra and Time Variations at Radio Frequencies

1972 ◽  
Vol 44 ◽  
pp. 232-248
Author(s):  
Beverley J. Harris
Keyword(s):  
Radio Galaxies ◽  
Radio Sources ◽  
Optical Identification ◽  
High Frequencies ◽  
Compact Component ◽  
Sky Survey ◽  
Time Variations ◽  
Radio Frequencies ◽  
Luminous Objects ◽  
Interplanetary Scintillations

Accurate relative spectra for 300 radio sources from the Parkes catalogue have been measured and a statistical study made of their relation to class of optical identification and to other radio properties. Individual spectra and their time variations have also been investigated.The results support the contention that radio sources for which no identification appears on the Palomar Sky Survey prints may be galaxies more luminous at radio frequencies than those which are identified. From a study of QSOs, radio galaxies and these blank field objects, it appears (a) that with increasing radio luminosity compact components are more often found, their presence being indicated by synchrotron self-absorption at low and high frequencies, by flat, variable spectra at high frequencies, and by interplanetary scintillations; and (b) that where no compact component contributes to the spectrum at high frequencies, many spectra steepen with increasing frequency, an effect which may be more marked for the more radio luminous objects.Detailed analyses of the time variations in the compact components of 22 variable sources are generally consistent with the adiabatically expanding, uniform sphere model of Shklovsky, Kellermann, van der Laan and others. The model was modified to include relativistic expansion according to the formulae given by Rees and Simon. The results suggest that these components have evolved within months or years, have linear dimension of 0.1 to 100 pc and magnetic fields of 1 to 10−4 G. Some spectra at frequencies above 5000 MHz suggest non-adiabatic expansion which may be the result of continued injection of energy into an expanding region.

scholarly journals Catalogue with visual morphological classification of 32,616 radio galaxies with optical hosts

2019 ◽  
Vol 15 (S356) ◽  
pp. 361-363
Author(s):  
Natalia Żywucka ◽  
Dorota Koziel-Wierzbowska ◽  
Arti Goyal
Keyword(s):  
Signal To Noise Ratio ◽  
Radio Galaxies ◽  
Sloan Digital Sky Survey ◽  
Radio Sources ◽  
Type I ◽  
Host Galaxies ◽  
Contour Maps ◽  
Narrow Angle ◽  
Sky Survey

AbstractWe present the catalogue of Radio sources associated with Optical Galaxies and having Unresolved or Extended morphologies I (ROGUE I). It was generated by cross-matching galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR 7) as well as radio sources from the First Images of Radio Sky at Twenty Centimetre (FIRST) and the National Radio Astronomical Observatory VLA Sky Survey (NVSS) catalogues. We created the largest handmade catalogue of visually classified radio objects and associated with them optical host galaxies, containing 32,616 galaxies with a FIRST core within 3 arcsec of the optical position. All listed objects possess the good quality SDSS DR 7 spectra with the signal-to-noise ratio > 10 and spectroscopic redshifts up to z = 0.6. The radio morphology classification was performed by a visual examination of the FIRST and the NVSS contour maps overlaid on a DSS image, while an optical morphology classification was based on the 120 arcsec snapshot images from SDSS DR 7.The majority of radio galaxies in ROGUE I, i.e. ∼ 93%, are unresolved (compact or elongated), while the rest of them exhibit extended morphologies, such as Fanaroff-Riley (FR) type I, II, and hybrid, wide-angle tail, narrow-angle tail, head-tail sources, and sources with intermittent or reoriented jet activity, i.e. double–double, X–shaped, and Z–shaped. Most of FR IIs have low radio luminosities, comparable to the luminosities of FR Is. Moreover, due to visual check of all radio maps and optical images, we were able to discover or reclassify a number of radio objects as giant, double–double, X–shaped, and Z–shaped radio galaxies. The presented sample can serve as a database for training automatic methods of identification and classification of optical and radio galaxies.

scholarly journals Optical Identification Strategies for the Molonglo Cluster Survey

1997 ◽  
Vol 14 (3) ◽  
pp. 221-229 ◽  
Author(s):  
A. J. Haigh ◽  
J. G. Robertson ◽  
R. W. Hunstead
Keyword(s):  
Production Rate ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Optical Identification ◽  
Strong Concentration ◽  
Sky Survey ◽  
Extended Sources ◽  
Abell Cluster ◽  
Absolute Magnitudes ◽  
Optical Identifications

AbstractWe describe a newly refined procedure for making optical identifications of radio sources in Abell cluster fields observed with the Molonglo Observatory Synthesis Telescope (MOST). The method is based on past experience but uses a range of new tools to improve the reliability and production rate of identification lists. The COSMOS/UKST Southern Sky Object Catalogue was used to make preliminary identifications which were then inspected visually with the assistance of computer generated overlays of the MOST images and the Digitized Sky Survey (DSS). The overlaid images were essential for securing identifications for the extended sources prevalent among nearby clusters.We find 21±1·5% of the radio sources are identified with galaxies and 4·6±0·7% with QSO candidates in a sample of 927 radio sources in 27 cluster fields. We make a preliminary attempt to separate cluster radio galaxies from interlopers on the basis of absolute magnitudes. A strong concentration of radio galaxies was found at projected distances less than 100 kpc from the cluster centres and a weaker concentration for projected distances of 100–500 kpc.

Introduction

2018 ◽  
Author(s):  
Jill Hicks-Keeton
Keyword(s):  
Jewish History ◽  
Jewish People ◽  
Second Temple ◽  
Second Temple Period ◽  
A Minor ◽  
Joseph And Aseneth ◽  
Literary Phenomenon ◽  
Minor Character

The Introduction claims that the ancient romance Joseph and Aseneth moves a minor character in Genesis from obscurity to renown, weaving a new story whose main purpose was to intervene in ancient Jewish debates surrounding gentile access to Israel’s God. Aseneth’s story is a tale of the heroine’s transformation from exclusion to inclusion. It is simultaneously a transformative tale. For Second Temple-period thinkers, the epic of the Jewish people recounted in scriptural texts was a story that invited interpretation, interruption, and even intervention. Joseph and Aseneth participates in a broader literary phenomenon in Jewish antiquity wherein authors took up figures from Israel’s mythic past and crafted new stories as a means of explaining their own present and of envisioning collective futures. By incorporating a gentile woman and magnifying Aseneth’s role in Jewish history, Joseph and Aseneth changes the story. Aseneth’s ultimate inclusion makes possible the inclusion of others originally excluded.

scholarly journals CNN architecture comparison for radio galaxy classification

2021 ◽  
Vol 503 (2) ◽  
pp. 1828-1846
Author(s):  
Burger Becker ◽  
Mattia Vaccari ◽  
Matthew Prescott ◽  
Trienko Grobler
Keyword(s):  
Comparative Study ◽  
Galaxy Evolution ◽  
Radio Galaxy ◽  
Recognition Performance ◽  
Model Complexity ◽  
Great Promise ◽  
Radio Sources ◽  
Morphological Classification ◽  
Computational Performance

ABSTRACT The morphological classification of radio sources is important to gain a full understanding of galaxy evolution processes and their relation with local environmental properties. Furthermore, the complex nature of the problem, its appeal for citizen scientists, and the large data rates generated by existing and upcoming radio telescopes combine to make the morphological classification of radio sources an ideal test case for the application of machine learning techniques. One approach that has shown great promise recently is convolutional neural networks (CNNs). Literature, however, lacks two major things when it comes to CNNs and radio galaxy morphological classification. First, a proper analysis of whether overfitting occurs when training CNNs to perform radio galaxy morphological classification using a small curated training set is needed. Secondly, a good comparative study regarding the practical applicability of the CNN architectures in literature is required. Both of these shortcomings are addressed in this paper. Multiple performance metrics are used for the latter comparative study, such as inference time, model complexity, computational complexity, and mean per class accuracy. As part of this study, we also investigate the effect that receptive field, stride length, and coverage have on recognition performance. For the sake of completeness, we also investigate the recognition performance gains that we can obtain by employing classification ensembles. A ranking system based upon recognition and computational performance is proposed. MCRGNet, Radio Galaxy Zoo, and ConvXpress (novel classifier) are the architectures that best balance computational requirements with recognition performance.

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