Cambridge Catalogue Research Articles

THE REVISED 3C CATALOG OF RADIO SOURCES: A REVIEW OF OPTICAL IDENTIFICATIONS AND SPECTROSCOPY.

ABSTRACT We present a catalog of the important optical data for the radio sources in the Revised Third Cambridge Catalog. Optical positions, redshifts, magnitudes, and identifications have been included, as well as radio flux densities and spectral indices for the sample of 297 extragalactic 3CR sources. A bibliography of optical identifications, spectroscopy, and radio position/structure is also given. In addition to the literature compilation, we present new spectroscopic observations of 27 3CR radio galaxies, 25 of which do not have previously published redshifts.

Australian Journal of Physics Astrophysical Supplements Number 22, May 1972

Observations at 408 MHz of radio sources from the 4C catalogue. IV. Declination range 20� to 0�. By R. E. B. Munro Abstract. Radio positions and flux densities measured at 408 MHz with the Molonglo radio telescope are given for 1392 sources from the Fourth Cambridge catalogue in the declination range 20� to 0�. The mean spectral indices between 178 and 408 MHz are also considered in the light of these improved flux densities.

The Log S–log z Diagram for Radio Galaxies and its Relation to Cosmology

An examination of the flux S and redshift z of radio galaxies in the third Cambridge catalogue lends some encouragement to the steady state cosmology.

The Spectra of Radio Sources in the Revised 3c Catalogue

Accurate values of the flux density are given for nearly all sources in the Revised Third Cambridge Catalogue at frequencies of 38, 178, 750, 1400, 2695, and 5000 MHz. These have been used to determine the spectrum of each source over this frequency range. It is concluded that the form of the spectra in many sources is determined not only by the energy distribution of relativistic electrons but also, as a result of self-absorption, by their spatial distribution. Sources identified with quasi-stellar objects have a wider dispersion of spectral indices than those identified with radio galaxies, particularly at the higher fre- quencies. Among the radio galaxies, the intrinsically strongest sources appear to have the steepest spectra. Unidentified sources have steep spectra similar to those of the stronger radio galaxies, and they are probably distant galaxies

The Radio Spectra of Sources in the Fourth Cambridge Catalogue, II

The Radio Spectra of Sources in the Fourth Cambridge Catalogue, II

The Source Counts from the 4C Survey

Abstract The source counts derived from the fourth Cambridge catalogue of radio sources (4C) are presented and are combined with previously published results to give the number/flux density (log N/log S) curve over the range of flux density 0.27 < S < 35 × 10−26(c/s)−1. The correction necessary to take account of confusion is deterrnined by a Monte Carlo process and the corrections for angular diameters of sources and source clustering are also discussed. On the assumption that the form of the source counts can be explained by density variation with epoch, forms of this density variation are derived which would be consistent with the latest derivation of the luminosity distribution function.

A Double Radio Source with a Wide Component Separation

Moffet (1964, 1965) has recently drawn attention to two double radio sources which have unusually large ratios of separation to component size. One of these, 3C 33, an interferometric double, has an angular separation of 250". and a component size of 16", giving a ratio of 16 : 1. The distance of the parent galaxy is such that the physical separation of the two components is at least 200 kpc. The other double consists of the sources 3C 343 and 3C 343�1 (revised Third Cambridge Catalogue

The Farthest Quasar

The most distant object ever observed has been reported by M. Schmidt and T. A. Matthews of the Mount Wilson and Palomar Observatories. The faint (18th‐magnitude) object is a quasi‐stellar radio source designated as 3C147 in the Third Cambridge Catalogue of Radio Sources. The “quasars” are the most energetic objects ever found, and about a dozen of them are now known.

On the Identification of Extragalactic Radio Sources

Identifications of radio sources with galaxies and clusters of galaxies have been sought systematically in a limited region of the sky. The optical data have been taken principally from the National Geographic Society-Palomar Observatory Sky Atlas and a catalogue of clusters of galaxies prepared by Abell (1958) from the same Atlas. The radio data are taken from results obtained with the Sydney cross-type radio telescope, supplemented at times with additional information from a recent Cambridge Catalogue (3C). A total of 46 possible identifications with galaxies are listed and 55 possible identifications with clusters of galaxies, the great majority of which are new. Most of these galaxies are double systems, but no other common features could be recognized: it seems probable that many galaxies of completely normal appearance are very strong radio emitters. The possible nature of the double galaxies is discussed briefly and attention is drawn to a corresponding duplicity in the radio brightness distribution observed in some strong radio sources. In many cases the emission from clusters appears to be associated with a single galaxy or pair of galaxies in the cluster; evidence for the existence of radiation of intergalactic origin is inconclusive. A selection of the possible galaxy identifications has been used to derive a provisional radio luminosity function; it appears probable that there is no distinct class of " radio galaxies", but all radio luminosities appear to be represented, the numbers of radio sources in a given volume of space falling rapidly with increasing luminosity. A radio luminosity function of the form derived is capable of accounting for a substantial number of the radio sources of small size observed at high galactic latitudes; the remainder could be accommodated by the uncertainty in the data. It is found that, at the levels to which source counts can currently be taken, cosmological effects are likely to be small, although the most distant sources are markedly affected.

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

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.

Counts of Extragalactic Radio Sources and Uniform Model Universes

The radio sources are assumed to be galaxies sharing in the red-shift phenomenon. The counts of such sources to successive limits of flux density are interpreted in terms of the model universes of general relativity. The flux density in each infinitesimal interval of frequency is assumed to be proportional to a power of the frequency and to a multiplicative parameter, both these quantities being regarded as functions of the red-shift, i.e. of the time of travel of the radiation. All sources at the same distance from the observer are assumed to be identical radiators; this permits the introduction of a standard comparison source. The data in the Sydney catalogue can then be interpreted in terms of radio sources of constant strength�(i.e. which are independent of the red-shift) if they are similar to NGC 1275, taken as standard. If they are similar to Cygnus A, the data imply that the sources were radiating more strongly when their radiation left them than is Cygnus A now. This type of conclusion appears to be unavoidable for the data of the Cambridge catalogue. It is briefly explained how to modify the theory to take account of a variation with time of the space-density of sources and also of a mixture of comparison sources.

Notes on the Annelida Tubicola of the Wenlock Shales, from the Washings of Mr. George Maw, F.G.S.

The bibliography of this very interesting group of animal remains is comparatively scanty if compared with the literature of some other groups. In his celebrated ‘Petrefacten’ (1820) Schlotheim founded the genus Cornulites for the inclusion of “certain Silurian fossils of somewhat doubtful affinities, but apparently most nearly allied to the tubicolar annelids”. In the ‘Silurian System,’ published in 1839, species found in the Upper and Lower Silurian were identified with species described by Schlotheim; and since then authors have referred specimens to either Tentaculites or Cornulites . In ‘Siluria,’ and also in the ‘Cambridge Catalogue,rs Sailer rectified somewhat the earlier errors by showing that some at least of the casts of specimens had been referred to as separate species. In his ‘British Palæozoic Fossils’ M'Coy redefines and limits the species of previous authors; but he adds little to our knowledge of the group generally. It is to Prof. Nicholson, whilst working amongst the American Palæozoic fauna, that we owe the most detailed account of Tubicolar Annelida, and that from material collected by himself. In working over the species which had previously been identified as Tentaculites he first saw the necessity of founding new genera for their reception. Tentaculites was redefined and limited, and Prof. Nicholson separated this group from ordinary Tubicolar Annelida; but I am not prepared to say that Tentaculites belongs to the Pteropoda. Following, however, the example set by Nicholson, I shall keep them separate, and deal with their structural peculiarities further on. The new genera founded by Nicholson are Conchicolites and Ortonia .

A Review and Description of the various Species of British Upper-Silurian Fenestellidæ

I have been recently engaged in investigating some of the Palæzoic Polyzoa, more particularly the Upper-Silurian Fenestellidæ: the result I beg to lay before the Society. The Silurian group of the Fenestellidæ has by no means proved hitherto so interesting a field for research as the Carboniferous series. I find that only three palæontologists have entered the field—Lonsdale, Portlock, and Prof. M'Coy. The former, in Murchison's ‘Silurian System,’ gives an account of four species of Fenestella and two allied forms, which are most likely Fenestellœ . Prof. M'Coy, in the Cambridge Catalogue, describes two more species, and Portlock one from the Silurian strata in Ireland, making nine species in all, viz.:— Fenestella antiqua, Lonsd. , Murch. Sil. Syst. pl. 15. fig. 16. —Milleri, Lonsd. , ibid. pl. 15. fig. 17. —prisca, Lonsd. , ibid. pl. 15. figs. 15, 18. —reticulata, Lonsd. , ibid. pl. 15. fig. 19. Retepora infundibulum, Lonsd. , ibid. pl. 15. fig. 24. Gorgonia assimilis, Lonsd. , ibid. pl. 15. fig. 27. Fenestella rigidula, M'Coy , Brit. Pal. Foss. pl. 1 c. fig. 19. —patula, M'Coy , ibid. pl. 1 c. fig. 20. Gorgonia regularis, Portl. , Geol. Londonderry, p. 324, pl. 22. fig. 3. Prof. M'Coy's portion of the work has the advantage of being full, clear, and definite. On the other hand, Lonsdale, from causes to which I shall allude, has not been so fortunate or successful in his descriptions. Indeed the work of Lonsdale in arranging the Fenestellœ of the Murchison collection can only be regarded as provisional. With the scanty material