bluuebunny/crossref_metadata_2025 huggingface dataset:
A Dynamo Model for the Large Scale Fields
Authors: Csada I. K.
Published: July 2016

The expansion of the magnetic field in a series of force-free constituents for the internal field and that of ‘semi’ force-free constituents for the external field results in the skew symmetry of the coupling tensor of a magnetohydrodynamic dynamo. The periodic solution which exists in this case is deduced by the method of eigenvalues. Based on the numerical results a dynamo model is proposed to draw up the characteristic features of the magnetographic observations carried along the central meridian and at the polar areas.
Structure, Dynamics and Statistical Properties of Galaxies
Authors: De Vaucouleurs G.
Published: July 2016

The following empirical or physical parameters describing individual and statistical properties of galaxies are reviewed: morphological type including new or revised types; intrinsic luminosity distribution functions of two main components (spheroid and disk); true ellipticities of different types; characteristic scale parameters (effective diameter and luminosity density) of spheroidal and flat systems; masses and densities of spheroidal, disk and mixed systems from velocity dispersion and rotation velocities; rotation periods, maximum rotation velocities, angular velocities and momenta of different types; neutral hydrogen masses and densities; spectral energy distributions and colour indices; number of independent parameters from principal component (factor) analysis; luminosity functions and selection effects; clustering and space distribution; maximum density-radius and velocity dispersion-radius relations in systems of galaxies.
The Formation of Disks by Inelastic Collisions of Gravitating Particles. Applications to the Formation of Galaxies
Authors: Brahic André
Published: July 2016

The numerical study of a gravitating system of colliding particles has many potential applications, for instance the formation of flat galaxies, the formation of the solar system and the evolution of Saturn's rings. Preliminary results are presented for the galactic case. The system tends towards a final equilibrium state and it seems that such a collision mechanism can flatten a protogalaxy.
Dynamics of Rotating Stellar Systems: Collapse and Violent Relaxation
Authors: Gott J. Richard
Published: July 2016

Axisymmetric systems, having differing amounts of initial angular momentum and containing 2000 stars (mass points) each, are allowed to collapse under their own gravitational attraction. Collapse and violent relaxation are found to lead to the formation of equilibrium structures after only a few free-fall times. The systems contain a sufficient number of mass points so as to be effectively collisionless and the equilibrium structures are consistent with accurate satisfaction of the stationary collisionless Boltzmann equation. Rotating equilibrium models produced in this way resemble elliptical galaxies, with elliptical isophotes. With cosmologically reasonable amounts of initial angular momentum, E0 to E4.5 galaxies can be produced. The equilibrium models show rotation curves in general agreement with that expected from violent relaxation theory. In particular the models show a central region with solid-body rotation. Further out, the systems become differentially rotating. When infall effects are included one can produce models with extended envelopes in good agreement with observed elliptical galaxies. It is suggested that the crucial factor in determining whether an elliptical or a spiral galaxy is formed is whether or not star formation is complete by the time the proto-galaxy reaches its point of maximum collapse.
Models for the Formation and Evolution of Spherical Galaxies
Authors: Larson Richard B.
Published: July 2016

Detailed dynamical model calculations based on a conventional collapse picture of galaxy formation, and conventional assumptions concerning star formation and stellar evolution, are found to be able to reproduce satisfactorily the basic structural and photometric properties of elliptical galaxies. The quasar phenomenon may be identifiable with the formation of the nucleus of a giant elliptical galaxy.
Fine Structure Within the Redshift-Magnitude Correlation for Galaxies
Authors: Tifft W. G.
Published: July 2016

Previous work on the redshift-magnitude banding correlation is briefly reviewed. New tests of the concept are applied successfully to a second cluster (A2199) and the outer portions of the Coma cluster. Using more than 200 redshifts in Coma, Perseus, and A2199 the presence of a distinct band-related-periodicity in redshift is indicated. Finally, a new sample of accurate redshifts of bright Coma galaxies on a single band is presented, which shows a strong redshift periodicity of 220 km s−1. An upper limit of 20 km s−1 is placed on the internal Doppler component of motion in the Coma cluster.

Redshift-magnitude bands are, therefore, now recognized to consist of discrete ‘spin states’ organized into ‘spin groups’ which show strong morphological associations. Bands are probably in turn organized into band systems. The individual spin states are suggested to represent distinct configurations of matter at the nuclear or fundamental particle structure level. Transitions between states in a time systematic sense of decreasing redshift (increasing internal binding) are suggested to occur in galaxy nuclei. Energy released in such transitions may be the driving energy in radio sources and related objects.
Theory of Galactic Nuclei
Authors: Saslaw William C.
Published: July 2016

This paper reviews current ideas about the possible constituents of galactic nuclei, and the mechanisms for ejecting gas and massive objects.
Structures of Central Bulges and Nuclei of Galaxies
Authors: De Vaucouleurs G.
Published: July 2016

The isophotal surfaces of central bulges of normal spirals, often described as ‘spheroidal’, are shown to depart from ellipsoids of revolution and to resemble MacLaurin or Jacobi spheroids with zonal distortion; two typical examples, NGC 4565, 5746, are illustrated. Weaker examples are NGC 2683, 4594 and 891. Stronger examples are NGC 7332 and 128.

The true nucleus of an ordinary spiral is at most a very small object (~ 10 pc) resolved only in the nearest galaxies. The apparently larger nuclei seen in more distant spirals and lenticulars, in particular the so-called N-types, are probably artifacts due to insufficient resolution. It is possible that even in M31 the small ‘nucleus’ is merely the seeing-convolved image of the central peak in the r1/4 luminosity distribution of the spheroidal component.

In the nearest barred lenticulars and early spirals each large ellipsoidal ‘nucleus’ (~ 1.0 × 1.5 kpc) in the centre of the bar or central lens is found to include a second bar and inner nucleus on a smaller scale, in the approximate ratio of the corresponding Jeans' lengths. This is illustrated by high resolution photographs of NGC 1291; another example is NGC 1326.
UBV Photometry of Mars
Authors: Young A. T.
Published: July 2016

A critical analysis of selected high-quality photometric observations of Mars indicates that: (1) The phase function is concave upward out to at least 40° phase. No sudden brightening occurs at opposition, but the curvature increases at small phase. (2) Large systematic differences (0.1–0.2 mag.) exist between different observers' data. However, the small random scatter attributable to Mars (0.01–0.02 mag.) in the better series suggests that these differences represent systematic errors in data reduction, not variations in the planet's brightness. (3) The disentangling of seasonal, diurnal, and phase effects leaves considerable ambiguity; more observations are needed, over a long time, with a stable instrumental system. However, even the present data are sufficient to expose substantial errors in published phase curves of Mars (and consequently, in interpretations based on them).
On the Equation of State of Hydrogen and its Use in Models of Major Planets
Authors: Hawke R. S.
Published: July 2016

Since Jupiter and Saturn are considered to be composed primarily of hydrogen, its pressure-density equation of state is needed for computational models of their interiors. Until recently, experimental data were limited to 20 kbar statically and 40 kbar dynamically. Since the majority of a major planet is at a pressure in excess of this, there were only theoretical calculations available for modeling.

Wigner-Seitz type calculations have been shown to be accurate at determining the equations of state of the alkali metals. Hence, it has been assumed that the equation of state of metallic hydrogen can be calculated in the same way with fair confidence. However, the molecular hydrogen equation of state has been much more ellusive. The many attempts at modeling the interatomic forces have led to rather scattered pressure density relationships.

The planetary model situation is further complicated by the expectation that the transition from the molecular to the metallic phase will be in conjunction with a relatively large density change.

Recently, data from new experiments have become available; in one case up to 8 Mbar. The data are not in disagreement with many calculations on hydrogen, but the resolution is not yet adequate to determine accurately and confidently, the pressure and the densities of the molecular to metallic phase transition. The accuracy of these parameters in turn affect the models of the planetary interiors, such as the radii of the metallic sphere and high density core.

This paper will discuss the details of these relations and the possible affects of the speculative properties of metallic hydrogen.
Jupiter's Radiation Belts and Upper Atmosphere
Authors: Degioanni Joseph J. , Dickel John R.
Published: July 2016

Models of Jupiter's radiation belts have been constructed to determine the distribution of particles and their energies which will produce the observed decimetric radio emission. Data on the spectrum and the variation of emission with Jovian longitude have been used to show that the relativistic particles have a nearly isotropic distribution with high energies (of order 100 MeV) within 2 Jovian radii and a very flat distribution in the equatorial plane of low energy particles further out in the magnetosphere.

Subtraction of the emission predicted by this model from the total radio emission shows that the thermal contribution in the frequency range between 3000 and 10000 MHz is somewhat less than had been previously expected. (The brightness temperature of the planetary disk is 180 K at 3000 MHz, for example.) This suggests that the ammonia mixing ratio in Jupiter's upper atmosphere may be as high as 0.002.
Models of Saturn's Rings Which Satisfy the Optical Observations
Authors: Kawata Y. , Irvine W. M.
Published: July 2016

A theoretical model of Saturn's rings is investigated which includes the shadowing effect and realistic anisotropic phase functions for the ring particles. The effects of multiple scattering and the finite size of the Sun, including the penumbra, are rigorously included. The permissible range of the relevant parameters, including optical thickness, single scattering albedo, volume density, and phase function are investigated by comparing the theoretical results to observations of the ring brightness vs phase angle, wavelength, and elevation of the Sun and Earth. Anisotropic scattering by the ring particles is necessary in order to match the observations. The colour dependence of the opposition effect is interpreted in terms of the albedo spectrum of the ring particles.
Rationale for Nasa Planetary Exploration Program
Authors: Rasool I. , Herman D. , Kerrisk D. , Brunk W.
Published: July 2016

NASA program of future solar system exploration in the years 1973–1990 is presented.
Large-scale structure of spiral nebulae
Authors: Baade W.
Published: July 2016

For a discussion of the large-scale structure of spiral nebulae, we should like, of course, to choose a stellar system which we are certain is similar to our own. Since we know that our own Galaxy is a spiral galaxy, this narrows our choice to the spiral galaxies and, of those, we can immediately eliminate the so-called barred spirals, as we know that our galaxy is not a barred spiral. Hence, we need only consider spirals of types Sa, Sb, and Sc on Hubble's system. NGC 4594 is an Sa system with a large central spheroidal system typical of these early-type spirals. Undoubtedly, our Galaxy does not have such a large spheroidal system since it would be obvious as a large bulge which simply has not been observed. Next, M 81 is typical of the Sb spirals in which the central system has shrunk considerably. Finally, M 33 is typical of the Sc spirals in which the central system has shrunk until it actually approaches a semi-stellar point.
The distribution of atomic hydrogen in the galaxy
Authors: Van De Hulst H. C.
Published: July 2016

It is my privilege to report here about the investigations of the distribution of neutral hydrogen in the Galaxy. These observations, conducted by the Netherlands Foundation for Radio Astronomy, were made at Kootwijk and reduced at the Leiden Observatory. More than a dozen persons have participated in this work during the past year. Among them are Prof. Oort and myself, but I should mention three in particular: C. A. Muller has perfected the instruments even further and has supervised the observations that were made during 24 hr a day. G. Westerhout has supervised most of the reductions at Leiden and has prepared the map and model of the outer parts of the Galaxy. M. Schmidt has unravelled the situation in the inner parts of the Galaxy, on the basis of his observations made for this purpose.
The radio emission from the galaxy and the andromeda nebula
Authors: Baldwin J. E.
Published: July 2016

Although the sources responsible for the radio emission from the Galaxy are unknown, it may nevertheless be valuable to make a comparison between the magnitude and distribution of the emission observed in our Galaxy and that of other nebulae. Analyses have already been made to relate the total emitted power from nearby nebulae with that from the Galaxy, and by considering the integrated radiation from well-defined clusters attempts were made to extend the comparison to the average emission from fainter nebulae.
Line Absorption Studies of the Interstellar Gas Near 1015 Hz
Authors: Jenkins Edward B.
Published: July 2016

The Copernicus satellite now opens up the ultraviolet region for inspection, and the number of resonance lines which may be studied has increased from 6, seen in the visible, to more than 30. The distribution and properties of an important constituent of the interstellar gas, molecular hydrogen, can be studied in detail using this instrument. A more comprehensive picture may now be developed for element depletion factors, electron densities, and sources of ionization (UV photons, low energy cosmic and X-rays).
Two New Recombination-Line Results
Authors: Kerr F. J. , Jackson P. D. , Knapp G. R. , Brown R. L.
Published: July 2016

This paper reports two new recombination-line results. The first is the detection of carbon line emission from the dark cloud near ϱ Ophiuchi, and the second discusses the origin of hydrogen recombination line emission associated with ionized gas outside known discrete continuum sources.
Theoretical Calculations of Interstellar Cloud Formation
Authors: Goldsmith Donald W.
Published: July 2016

Numerical calculations of the growth of thermal instabilities show that condensations tend to form with the proper sort of density contrast but the wrong shapes (and, to some extent, sizes) to qualify as the observed interstellar clouds analyzed by Heiles.
A High-Resolution Polarization Survey of the North Polar Spur
Authors: Westerhout G. , Bechis D.
Published: July 2016

Observations have been made at 21 cm with a resolution of 11′ to look for fine structure in the polarization distribution. In the North Polar Spur, the angular scale of the polarization parameters varies with latitude. This is attributed to an increase in the irregularity of the magnetic field in the Spur with latitude.
Recent Radio Observations of Galactic H ii regions
Authors: Churchwell E.
Published: July 2016

The structure and physics of Hiiregions are reviewed. The discussion is principally based on the radio mapping of intermediate-size Hiiregions to measure the energy balance, the mapping of small-scale structure by aperture-synthesis techniques to define the ionization conditions, and determination of helium abundances from radio recombination-line observations of H and He in Hiiregions.
High-Resolution Radio Observations of a Giant Hii Region in Cygnus
Authors: Baars Jacob W. M. , Wendker Heinrich J.
Published: July 2016

Westerbork observations of several large Hiiregions in the Cygnus-X region are described. IC 1318 appears to be a giant Hiiregion, and two nearby sources may be genetically related to it.
The Hiiregions of M31
Authors: Spencer J. H. , Burke B. F.
Published: July 2016

The luminosity of the brightest Hiiregions of M31 was determined with the NRAO 3-element interferometer at 3.7 cm and 11 cm wavelength. It is unlikely that M31 has any superbright Hiiregions such as W51 or W49; our Galaxy has between 10 and 20 Hiiregions that are more luminous than any in M31.
Large-Scale Expansion in the Carina Nebula
Authors: Huchtmeier W. K. , Day G. A.
Published: July 2016

Radio recombination line observations of the Carina nebula at 6 cm and 3.4 cm were made at Parkes. Around Carina II the profiles are separated by as much as 45 km s-1. This is interpreted as expansion in the H ii region.
Decimeter-Wavelength Studies of Recombination Lines
Authors: Terzian Yervant , Pankonin Vernon
Published: July 2016

The results of new studies of decimeter wavelength Hnα and Cnα lines toward galactic nebulae are reported. The observations were made with the 305-m radio telescope of the Arecibo Observatory at 430 MHz (247α and 248α) and 606 MHz (221α). Selected positions in W51, W49, and the Rosette nebula were observed. The observed lines exhibit no pressure broadening; however, this is consistent with the interpretation of the data.
A 160-Mhz Map of Cas A
Authors: Hirabayashi H.
Published: July 2016

A rotational synthesis map of Cas A was obtained at 160 MHz with a resolution of 2 × 3′.
Stellar X-Ray Sources
Authors: Tananbaum Harvey D.
Published: July 2016

Data are presented for Cygnus X-1, Cygnus X-3, and Scorpius X-1 from radio to X-ray wavelengths. The evidence for Cygnus X-1's being a black hole is now quite convincing. New data for Cygnus X-3 show the presence of X-ray activity at the time of the giant radio outburst. The data for Scorpius X-1 show a close correlation between the X-ray and optical behavior, but coverage was not sufficiently complete to fully assess the relationship (if any) between the X-ray and optical emission and the radio emission.
Some High-Velocity Sources of 1612 MHz OH Emission
Authors: Kerr F. J. , Bowers P. F.
Published: July 2016

A pilot survey was made to study the feasibility of using radio observations of OH/IR stars to investigate the galactic distribution and kinematics of these presumably intermediate-population objects. Seven new sources were found, four near the center, two near l = 30°, and one at l = 128°.
Infrared Radiation from the Galactic Center
Authors: Borgman J.
Published: July 2016

IR observations of the region within 0°.5 of Sgr A are discussed. The total IR luminosity is 150 × 106L⊙. Most of it is stellar radiation, absorbed by low temperature dust and reradiated in the IR. There is no unique interpretation for the highly structured infrared core. It may comprise compact infrared sources like those in some Hn regions, or the structure may simply result from the dust distribution. Nonthermal radiation is also feasible, but a tradeoff between source luminosity and extinction is possible and prevents a final decision on this question.
The Galactic Centre at 408 MHz
Authors: Little A. G.
Published: July 2016

The Molonglo radio telescope has been used to map the galactic centre region with a resolution of 2.9′. Although similar to microwave maps of comparable resolution, there are differences. In particular, the source G1.05-0.1 is not visible at microwaves, and the source G0.1-0.0 is not visible at 408 MHz. The flux values of all the other sources around Sgr A confirm that they are thermal and that the sources G0.7−0.0, G0.5 − 0.0, and G0.2−0.0 are optically thick.

A more extensive galactic background survey with the cross shows the existence of a peak in the background emission with a brightness temperature of about 500 K at the galactic centre. This is probably the nonthermal source observed at 85 MHz. The higher-resolution observations of this map show the narrower, hotter region which appears on the microwave map and which surrounds Sgr A. This has a brightness temperature of 2100 K, which cannot be accounted for by a simple thermal spectrum extrapolated from microwaves.
Observations of the J = 6 to 5 Line of OCS in SGR B2
Authors: Akabane Kenji , Morimoto Masaki , Nagane Kiyoshi , Kaifu Norio
Published: July 2016

The J = 6 to 5 line of OCS at 72.9768 GHz was detected in Sgr B2 with antenna temperature 0.3 K, velocity + 62 km s-1, and velocity half width of ∼ 25 km s-1.
A Simple Interpretation of the ‘Rolling Motions’
Authors: Yuan C. , Wallace L.
Published: July 2016

The rolling motion phenomenon is interpreted as an apparent motion in the observations. It is caused by (i) the combined effect of the differential rotation and the bending of the galactic plane for the spiral arms beyond the solar circle, or (ii) the displacement of the spiral arms from the central galactic plane for those within the solar circle.
High Velocity Neutral Hydrogen Clouds
Authors: Davies R. D.
Published: July 2016

A review is given of the observations of neutral hydrogen high velocity clouds (|ν| > 80 km s−1) in and near the Galaxy. The positive and negative clouds are seen to have different distributions in the sky, following roughly the velocity pattern of galactic rotation. A characteristic of the majority of the clouds is their distribution in elongated bands or strings. The various theories of origin of HVCs are discussed; the possible role of the tidal interactions between the Magellanic Clouds and the Galaxy is emphasized. Tests are suggested to distinguish between the Oort theory of the infall of intergalactic material and theories which envisage the HVCs as originating in the outermost spiral structure.
The Magellanic Stream
Authors: Mathewson D. S. , Cleary M. N. , Murray J. D.
Published: July 2016

A southern sky survey of Hiin the velocity range − 340 km s−1 to + 380 km s−1 has shown that a long filament of H iextends from the Small Magellanic Cloud (SMC) region down to the South Galactic Pole and connects with the long Hifilament discovered recently by Wannier and Wrixon (1972) and van Kuilenberg (1972). There is also some evidence that this continues on the other side of the Magellanic Clouds and crosses the galactic plane at l = 306°. This filament, which follows very closely a great circle over its entire 180° arc across the sky, is given the name ‘The Magellanic Stream’. It may have been produced by gravitational interaction between the SMC and the Galaxy during a close passage (20 kpc) of the SMC some 5 × 108 yr ago, although it is impossible to account for the observed radial velocities along the Stream unless some force other than gravity is invoked to act on the Stream as well.
Rotating Gas and the Shapes of Radio Sources
Authors: Sparke L. S.
Published: July 2016

The power for a strong extragalactic radio source comes from deep within the nucleus, but the extended radio structure is clearly related to the larger-scale properties of the galaxy in which it lives. Very large sources are found in elliptical rather than spiral galaxies, and big galaxies have stronger radio sources than small ones. The narrow jets mapped in weaker radio galaxies do not expand with a constant opening angle, but become better focussed along their length, suggesting that they are confined by an external pressure. This paper discusses how the rotation of a radio galaxy affects the distribution of gas within it, and consequently the radio structure in elliptical and Seyfert galaxies. A model is proposed which leads to a specific prediction, relating the width of radio jets to the rotation speed of the galaxy in which they lie.
Observations of Radio Galaxies and QSR with Ratan-600
Authors: Soboleva N. S. , Parijskij Y. N.
Published: July 2016

We shall tell you briefly about the main observational program connected with radio galaxies. Different theories of radio galaxies predict different types of spectral index variations across the main body of the source. One would expect that the best solution of the problem is the construction of two-dimensional maps at a number of frequencies. However, we suggest that in some cases (i.e., for standard well-aligned structures) one-dimensional images with filled aperture may be much more accurate in determination of the variations of the spectral index along the major axes of radio galaxies. We now have 47 one-dimensional multifrequency images of all sources brighter than 1 Jy at centimeter wavelengths in the declination range −43° −+53° resolvable with our beam. Up to 7 frequencies were used (1.35, 2.08, 3.9, 6.5, 8.2, 13, and 31 cm). Cyg A is the best example showing structures of different scale: nuclear sources, bridges, main bubbles, and hot spots.
High Resolution VLA Observations of Quasars with Distorted Radio Stucture
Authors: Stocke J. , Christiansen W. , Burns J.
Published: July 2016

Most quasars with extended radio structures have the classical linear double structure (Class II) which is also characteristic of the most luminous radio galaxies. A very small fraction of quasars do, however, show deviations from the classical double structure which are similar to the distortions observed in some low luminosity radio galaxies, e.g., bent double sources. Among radio galaxies, structural distortions seem to be associated with membership in a cluster of galaxies. Indeed, Scott and Hintzen, 1978, have suggested that such distortions might be indicators of cluster membership for quasars as well. To test this hypothesis and examine the physics of distorted quasars, we have mapped the quasars 3C 270.1 and 3C 275.1 in both I and P using the VLA A-Array at 20 cm and 6 cm. Our high resolution (0.1 arc sec at 6 cm) and high dynamic range (200:1) observations demonstrate that the displaced components reported previously for these sources are indeed connected with the quasars themselves and, therefore, the distortions are not simply projection effects. We also report the discovery of a very narrow northwesterly pointing jet in the quasar 3C 275.1.
Multi-Frequency Polarization Studies of Radio Galaxies
Authors: Pooley G. G.
Published: July 2016

This is a brief report on some of the work in progress at Cambridge, with emphasis on studies of extragalactic radio sources using the One-mile and 5-km telescopes; together with the 6C survey and a new instrument now being commisioned at 151 MHz, we have a frequency range of 100:1 available for high-resolution mapping. The 6C survey has resulted in the discovery of a number of giant radio galaxies, most notably NGC 6251. At 151 MHz, the beautiful jet is not prominent; we have mapped it with the One-mile and 5-km instruments and a paper (by Saunders et al.) will shortly appear in Monthly Notices. Dr Willis will speak later on the structure of this source.
A Complete Sample of Radio Galaxies
Authors: Shaver P.A. , Danziger I.J. , Ekers R.D. , Fosbury R.A.E. , Goss W.M. , Malin D. , Moorwood A.F.M. , Wall J.V.
Published: July 2016

We report here some preliminary results of a multi-wavelength study of a complete sample of radio galaxies. The sample is comprised of 93 radio sources from the Parkes 11 cm catalog which are identified with galaxies of 17th magnitude or brighter in the declination zone −17° to −40°. Our objective is to cross-correlate the radio, infrared, optical, and other properties of a properly defined sample of radio galaxies.
Proton-Proton Collisions in Extragalactic Radio Sources
Authors: Okoye S. E. , Okeke P. N.
Published: July 2016

The majority of extragalactic radio sources are known to consist of two extended components straddling an optical galaxy or quasar with each component being maintained from the nucleus of the associated optical object through a beam or jet of relativistic plasma and magnetic fields. Hitherto, the energetics of radio source components have been considered essentially from the point of view of the cooling of the relativistic electrons through their interaction with ambient magnetic fields (synchrotron radiation) and with low energy photons (inverse Compton emission). Here we consider a hitherto neglected problem involving the mutual interactions between the fast particles themselves. (The results of a detailed investigation into these interactions will be reported elsewhere — see Okoye and Okeke, 1982.)
Radio and X-Ray Observations of Large Scale Jets in Quasars
Authors: Wardle J. F. C. , Potash R. I.
Published: July 2016

The first big radio jet to be found in a quasar was in 4C32.69 (z=.659) (Potash and Wardle, 1980). A new higher resolution map of this jet, made with the VLA at 5 GHz, is shown in Fig. 1. Observationally the important points are 1) it is very luminous, 2) it is very well collimated, 3) the magnetic field is parallel to the jet over its entire length, 4) it bends at least three times along its path to the outer radio lobe. Physically this is interesting because 1) it is a very lossy pipeline to the outer lobe, 2) the high degree of collimation suggests either the jet is confined by external pressure or it is highly supersonic. But the minimum internal energy density is very high (>3×10–10 erg cm–3), so if it is confined the external pressure must also be very high. On the other hand, if the jet is expanding freely, it is easy to show that the momentum flux is enormous (>4×1038 dynes). Such a jet is very rigid. It is difficult to stop and difficult to bend, but evidently both of these things happen. A detailed discussion of these problems is given in Potash & Wardle (1980), who concluded that the jet cannot be expanding freely. They suggested that the jet might be confined either by the thermal pressure of external hot gas, or by a helical component of magnetic field due to currents in the jet.
Recent WSRT and VLA Observations of the Jet Radio Galaxy NGC 6251
Authors: Willis A. G. , Strom R. G. , Perley R. A. , Bridle A. H.
Published: July 2016

NGC 6251, a 14th mag elliptical galaxy, was shown by Waggett et al. (1977) to have large-scale radio emission features with a total angular extent of ∼ 1.1°, which corresponds to a projected linear size of about 1.7 Mpc (HO = 75 km s−1 Mpc−1). A bright radio jet links a central core source embedded in NGC 6251 to the extended emission on the northwest side of the galaxy.
The Radio Core in 3C 236
Authors: Fomalont E. B. , Bridle A. H. , Miley G. K.
Published: July 2016

The two-kpc steep-spectrum radio core in the giant radio galaxy 3C 236 has been mapped with 0′.1 resolution using the VLA. The core morphology is substantially different from other radio cores and suggests that the flow of energy from the galactic nucleus may be continuous on one side and “blobby” on the other side.
The Compact Radio Structure of SS433
Authors: Schilizzi R.T. , Fejes I. , Romney J.D. , Miley G.K. , Spencer R.E. , Johnston K.J.
Published: July 2016

A campaign of VLBI observations of SS433 using the European network was begun in January 1980 and since October 1980 has continued at intervals of about two months except for the last two observations which were 6 days apart, see Table 1. The results of the first two epochs have been published in Nature (ref. 1), and those of the following six epochs are being prepared for publication.
SS433: Periodic Changes in the Radio Structure of Scale Size 1016 cm
Authors: Niell A. E. , Lockhart T. G. , Preston R. A. , Backer D. C.
Published: July 2016

Radio observations have clearly demonstrated that the kinematic twin-jet model (Milgrom 1979; Abell and Margon 1979) is the correct description of the general behavior of SS433 and have determined the orientation parameters that could not be obtained from the optical observations (Gilmore and Seaquist 1980; Hjellming and Johnston 1981 (HJ); Niell, Lockhart, and Preston 1981 (NLP)). Figure 1 shows the observed position angle of the radio jet at a distance of approximately from the core during the period 1979 May to 1981 May as determined from our VLBI measurements at 2.3 GHz. The mean position angle is 98°±2° for a 20° half-angle cone of precession about an inclination of 79° to the line of sight. The phase is consistent with the expected propagation time out to (1016cm) at a speed of 0.26c for a distance to SS433 of 5 kiloparsecs (HJ; NLP).
Instabilities in Pressure Confined Beams and Morphology of Extended Radio Sources
Authors: Ferrari A. , Massaglia S. , Trussoni E. , Zaninetti L.
Published: July 2016

Several authors have suggested that radio jet morphologies resolved in extragalactic sources are the effects of large-scale Kelvin-Helmholtz instabilities in high-speed, pressure-confined fluid beams ejected from parent active galactic nuclei (Ferrari et al. 1978, 1979, 1981; Hardee 1979;Benford et al. 1980). In particular results from studies for cylindrical geometries indicate how to connect the “wiggles” (observed in 3C449, NGC 6251, M87 and Cen A) with helical perturbations and the “knots” (observed in NGC 315, M87, Cen Aetc.) with pinching modes. Correspondingly small scale MHD perturbations, generated by the same instability or nonlinear cascade processes, are efficient in accelerating relativistic electrons via stochastic scatterings (Lacombe 1977; Ferrari et al. 1979). This picture may satisfy both the requirements for in situ re-acceleration and the intrinsic correlation between morphology and emission.
Galactic Centers and Twin-Jets
Authors: Kundt Wolfgang
Published: July 2016

A schematic model is suggested to describe the various activities in the centers of massive galaxies. Basic assumptions are that (i) a uniform model can account for all the observed phenomena, such as quasars, blazars, radio galaxies, Seyferts, and the centers of normal galaxies (with disks), (ii) activity in galactic centers is repetitive, and (iii) in-situ-acceleration of highly relativistic electrons (other than by adiabatic compression) has an insignificant efficiency, i.e. is ignorable.
High Resolution Observations of the Quasar 3C147
Authors: Preuss E. , Alef W. , Pauliny-Toth I. , Kellermann K. I.
Published: July 2016

We report here preliminary results of observations of the quasar 3C147 which were made at 6 cm with a resolution of about 1 milliarcsecond using a VLB interferometer system with four antennas in the USA and one in Europe. Our observations are shown in Figure 1 along with previously published maps on larger size scales. VLA observations made at 2 cm wavelength (Fig. 1a) show an extended feature lying about 0.5 arc-seconds (3.5 kpc) to the northeast of a bright core (Readhead et al. 1980), while VLBI observations made at 18, 50, and 91 cm (Readhead and Wilkinson 1980, Wilkinson et al. 1977, and Simon et al. 1980) show a jet-like feature extending about 0.2 arcsec (1 kpc) in the opposite direction (Fig. 1b). The 18 cm VLB observations also indicated the presence of a smaller elongated feature extending only 3 milliarcseconds (20 pc) again toward the northeast (Fig. 1c). We have observed 3C147 in March 1978 and again in April 1981 with a resolution of 0.7 and 1.5 milliarcsec respectively. The 1981 data (Fig. 1d) clearly show the double structure of the core as well as a lower surface brightness feature which can also be seen in the 18 cm map. Our 1978 data (Fig. 1e) has better resolution and shows considerable structure in the milliarcsec component, but due to the absence of phase information in these data, the details are not reliable and the orientation is uncertain by 180°. The orientation is, however, specified by reference to the 1981 data.
Compact Radio Sources: Their Use and Size
Authors: Johnston K. J.
Published: July 2016

Compact radio sources are both interesting from an astrophysical point of view and useful for geophysics. They propose some very interesting astrophysical questions as to their energy generation and transport. Their small size allows the measurement of their positions to unprecedented accuracy extending astrometric measurements of parallax and proper motions to further distances. These celestial “beacons” may be used to establish an almost inertial reference frame against which positions on the earth and the earth's motions such as Universal Time (UT1) and polar motion may be measured to centimeter scale accuracy. Finally these sources when used in conjunction with radio interferometry can allow precise time synchronization over global distances at subnanosecond accuracy.
Variable Radio Sources
Authors: Fanti R. , Padrielli L. , Salvati M.
Published: July 2016

Flux variations are a common feature of flat spectrum compact extra-galactic radio sources. Detailed analysis and quantitative comparisons with theoretical models (e.g. van der Laan, 1966) are difficult due to the complex characteristics of the flux variations, which generally appear to consist of different outbursts blended together in time. Nevertheless, the general consensus is that the basic process has been correctly identified and consists in an expansion of a synchrotron radiating plasma cloud of relativistic electrons and magnetic field partially opaque to its own radiation. The main differences between data and predictions of the theory are that the variations propagate too fast and with too large amplitude toward lower frequencies. This behaviour however may be indicative of continuous energy supply and consequent accelerated expansion.
Superluminal Motion in NRAO 140 and a Possible Future Method for Constraining HO and QO
Authors: Marscher Alan P. , Broderick John J.
Published: July 2016

NRAO 140 is a quasar (z = 1.258) which is among only 3 or 4 such objects (and the one with the highest z) which were detected at X-ray energies prior to the operation of the Einstein Observatory (Marscher et al. 1979). We obtained contemporaneous X-ray and radio VLBI observations of the source in early 1980, to determine whether Compton scattering within the radio source is the primary X-ray emission mechanism (Marscher and Broderick 1981b). Instead, we found that the radio parameters predicted more than 103 times more X-ray flux than was observed. Since the Compton calculation is independent of distance, and since the troublesome component was partially resolved (and hence not a high-brightness-temperature emitter), we found that relativistic motion aimed nearly directly toward the observer with Lorentz factor exceeding 4, needed to be invoked in order to bring the predicted Compton flux down to the observed level (Marscher and Broderick 1981a, b). Since relativistic motion is also the preferred explanation for the apparent superluminal expansion seen in some compact radio sources (e.g., M. Cohen, this volume; Marscher and Scott 1980; Kellermann and Pauliny-Toth 1981), we predicted that the compact components in NRAO 140 should appear to separate at a speed exceeding about 4c.
VLA Observations of the Palomar Bright Quasar Survey
Authors: Shaffer David B. , Green Richard F. , Schmidt Maarten
Published: July 2016

Green and Schmidt (Green 1976, and in preparation) have optically surveyed some 10000 square degrees of the northern sky to search for bright quasars. Their final sample contains about 100 quasars. The B magnitudes of the sample range from 13.1 to 16.5, with most in the range 15.0–16.2. The redshifts range from 0.03 to over 2, considerably concentrated toward smaller values (median of 0.18).
BL Lac Objects and Their Associated Galaxies
Authors: Weistrop Donna
Published: July 2016

CCD photometry of five BL Lac objects indicates that at least three, and possibly four, are located at the centers of giant elliptical galaxies. The redshift for one of these objects, 1218+304, is estimated. A lower limit is placed on the redshift of 1219+28, for which no associated galaxy has been detected. Separation of the galaxy emission from the total observed flux makes possible comparison of the optical — far red flux from the point source alone with radio and X-ray data. This comparison suggests the emission from 1727+50 and 1218+304 can be interpreted as due to direct synchrotron emission. Observations of a small group of galaxies associated with the BL Lac object 1400+162 are also discussed.
A Comparison of the Structures of 3CR Quasars and Blank Field Radio Sources
Authors: Owen F. N. , Puschell J. J. , Laing R. A.
Published: July 2016

The purpose of this communication is to update our knowledge of the radio structural properties of quasars and blank field radio sources (blank field ≡ any radio source without an identification on the Palomar Sky Survey prints). The quasar sample consists of all sources (25) with angular sizes greater than 10 arcsec in the list of Jodrell Bank quasars observed by Owen, Porcas and Neff (1978). The blank fields consist of 16 3CR sources also with structures >10 arcsec based on Cambridge 5 km telescope observations. The sources were selected in low-frequency surveys; their emission at ν < 1 GHz is dominated by extended components with steep spectra. Thus, both samples should be oriented randomly in space except for a slight bias to be in the plane of the sky.
Gravitational Lenses and Cosmological Evolution
Authors: Peacock J. A.
Published: July 2016

Empirical descriptions of cosmological evolution rely on an assumed relation between luminosity distance and redshift in order to derive the luminosity function and its epoch dependence. This relation is usually taken to be that of an idealised Friedmann cosmology, despite the obvious abundance of small-scale structure in the Universe. However, the assumption that the probability of a lensing event is negligible is now made less tenable with the discovery of the double and triple QSO's, both of which appear to have been magnified by factors of 10–15. With at least two events of this amplification in 1500 known quasars, it may be that a large fraction of observed QSO's have been magnified by significant amounts. Turner (1980) suggests that all evolutionary statistics (e.g. V/Vmax) may thus be misleading, although he considers only an illustrative model of the effect. The problem is that, even if the intrinsic probability of a lensing event is very low, the effect becomes important if the background density of faint sources rises sufficiently quickly. We must therefore calculate not only the intrinsic probability of a given amplification, but incorporate this with the luminosity function to see if lensing could be made dominant by selection effects.
Superluminal Velocities of Compact Radio Sources: A Gravitational Lens Effect
Authors: Barnothy Jeno M.
Published: July 2016

An intervening galaxy acting as a gravitational lens produces usually from a compact radio source two or four enlarged “crescent” shaped virtual images, which have the same surface brightness as the object, but look brighter, due to the lens caused enlargement of the object area in the image. Velocities between elements of a source being vector quantities, will also be seen enlarged, occasionally to superluminal velocities (Fig.1). It is as simple as that. (Barnothy and Barnothy 1971; Barnothy 1976.)
The Galactic Distribution of Wolf-Rayet Stars
Authors: Hidayat B. , Supelli K. , van der Hucht K.A.
Published: July 2016

On the basis of the most recent compilation of narrow-band photometry and absolute visual magnitudes of Wolf-Rayet stars, and adopting a normal interstellar extinction law in all directions, the galactic distribution of 132 of the 159 known galactic WR stars is presented and discussed.

The spiral structure is found to be more clearly pronounced than in earlier studies. Furthermore we find an indication of two spiral arms at r=4 and 6 kpc. There appears to be an asymmetry of the z-distribution of single stars with respect to galactic longitude.

The location of the WC8.5 and WC9 stars between 4.5 and 9 kpc from the galactic center is discussed in the context of Maeder's red supergiant to WR star scenario.
Corrections for Hydrostatic Atmospheric Models: Radii and Effective Temperatures of Wolf Rayet Stars
Authors: De Loore C. , Hellings P. , Lamers H.J.G.L.M.
Published: July 2016

With the assumption of planparallel hydrostatic atmospheres, used generally for the computation of evolutionary models, the radii of WR stars are seriously underestimated. The true atmospheres may be very extended, due to the effect of the stellar wind. Instead of these hydrostatic atmospheres we consider dynamical atmospheres adopting a velocity law. The equation of the optical depth is integrated outwards using the equation of continuity.

The “hydrostatic” radii are to be multiplied with a factor 2 to 8, and the effective temperatures with a factor 0.8 to 0.35 when Wolf Rayet characteristics for the wind are considered, and WR mass loss rates are used. With these corrections the effective temperatures of the theoretical models, which are helium burning Roche lobe overflow remnants, range between 30 000 K and 50 000 K. Effective temperatures calculated in the hydrostatic hypothesis can be as high as 150 000 K for helium burning RLOF-remnants with WR mass loss rates.
Preliminary Results of a New Study of the Intrinsic Properties of Wolf-Rayet Stars
Authors: Turner David G.
Published: July 2016

Results are presented of a semi-empirical investigation of the transformation relations between colors and magnitudes in Lindsey Smith's narrow band photometric system for WR stars and their corresponding parameters in the broad band UBV system. A preliminary application of these relations to the study of WR stars in open clusters indicates that the intrinsic colors of WR stars are slightly bluer than the values tabulated by Smith, and that single WN stars are less luminous than previously supposed.
Infrared (1.4–4.1μM) Spectra of Wolf-Rayet Stars
Authors: Williams P. M.
Published: July 2016

The spectra of a variety of Wolf-Rayet stars have been observed with ∼1% spectral resolution in the 1.4–4.1μm region using UKIRT. Strong lines due to ions of helium and carbon are observed and their relative strengths discussed. The He I singlet at 2.058μm is anomalously strong relative to other He I lines in WC stars and is responsible for the difference in the (H-K) colours of WN and WC stars. Emission line corrections to H, K and L magnitudes of different types are discussed. The Sanduleak 0 VI star ST 3 shows very strong C IV lines like the WC5 stars but not the strong He I.
An Explanation of the Radio Flux Mystery of HD 192163 and Empirical Models for WN Stars
Authors: Nugis T.
Published: July 2016

The radio flux value of the star HD 192163 (WN6) measured by Dickel et al. (1980) imposes strong restrictions on the possible mass outflow region models of this star.
Carbon Abundance in WC Stars
Authors: Nugis T.
Published: July 2016

A specific feature of WC stars is the presence in their spectra of strong subordinate series lines of carbon ions arising in transitions between comparatively high-lying states. The intensities of these lines suggest that carbon abundance must be comparatively high in WC star envelopes because subordinate series lines are already nearly transparent to radiation (escape probability coefficients βik are close to unity) and their intensities strongly depend on the abundance of C(Jki ∝ Nk). The resonance lines of carbon ions and the lines arising in the permitted transitions between the low-lying energy levels are in a wide abundance interval not very sensitive to abundance due to the fact that βik ≪ 1 for these transitions (Jki ∝ Nk/Ni). for 3 WC stars (HD 165763 (WC5), HD 192103 (WC8) and HD 164270 (WC9)) we carried out the same kind of model-fitting study as for the WN stars (reported earlier). We used the same empirical models, that is we assumed that also for them the wind reaches the terminal velocity at R ≃ 2 Ro (v = const for R ≥ 2 Ro) and that Te(R ≥ 2 Ro) = TIIe = 0.6 T∗, where T∗ denotes the core temperature. We took into account the ions (atoms) of He, H and C for determining the ionization structure in the envelope.