bluuebunny/crossref_metadata_2025 huggingface dataset:
Time Evolution of the Large-Scale Solar Magnetic Field
Authors: Altschuler Martin D. , Newkirk Gordon , Trotter Dorothy E. , Howard Robert
Published: July 2016

The six years of data from the Mt. Wilson Magnetic Atlas were analyzed in terms of surface harmonics. Between 1959 and 1962 the dominant harmonic corresponded to a dipole lying in the plane of the equator (2 sectors). There was also a significant zonal harmonic in which both solar poles had the same magnetic polarity, opposite to that at the equator. From the end of 1962 through 1964, the harmonic corresponding to 4 sectors was dominant. In 1965 and 1966, the harmonic of the north-south dipole became significant.
The Magnetic Field Structure in the Active Solar Corona
Authors: Schatten Kenneth H.
Published: July 2016

The structure of the magnetic field of the active solar corona is discussed with reference to optical and radio observations of the solar atmosphere. Eclipse observations provide evidence of fine scale structures in the solar atmosphere that appear to relate to the coronal magnetic field. The coronal magnetic field used for comparison is that field calculated from potential theory: the influence of solar activity upon the potential theory field is discussed with reference to observations of the Faraday rotation of a microwave signal from Pioneer 6 as it was occulted by the solar atmosphere. Evidence has been found suggesting the existence of expanding magnetic bottles located at 10 R⊙ above flaring active regions. The dynamics of these events is discussed. It is further suggested that these magnetic bottles are an important component in the solar corona.
Active Regions at Millimeter Wavelengths and the Measurement of Magnetic Fields
Authors: Kundu M. R.
Published: July 2016

Some properties of solar active regions at 9 and 3.5 mm wavelengths are discussed. The regions have excess brightness temperatures of up to 1000 and 700K at 9 and 3.5 mm wavelengths respectively. The background radiation at 3.5 mm is often seen to be ‘absorbed’ in regions closely coincident with Hα dark filaments on the disk. Interpretation of this ‘absorption’ as due to the large optical thickness of the overlying filamentary material leads to an estimate of electron density in the filaments. The active regions at millimeter wavelengths show almost one-to-one correspondence with the Ca-plage regions as well as with the regions of longitudinal magnetic fields on Mt. Wilson magnetograms. A comparison of the mm-λ maps with the magnetograms ‘smoothed’ with the beams of mm observations shows this correspondence in a striking manner. This relationship suggests the possibility of measuring chromospheric magnetic fields from the measurement of polarization at millimeter wavelengths.
On the Orientation of Magnetic Fields in Quiescent Prominences
Authors: Anzer Ulrich , Tandberg-Hanssen E.
Published: July 2016

The longitudinal component of the magnetic field in quiescent prominences has been measured directly with magnetographs using the Zeeman effect on selected spectral lines (Rust, 1966; Ioshpa, 1968; Harvey, 1969). We know that as a general rule the magnetic field enters the, largely-vertical, sheet-like quiescent prominence on one side and exits on the other. The field traverses the prominence plasma with components both along and at right angles to the long axis of the prominence. It is the purpose of this paper to describe observations that may indicate the relative importance of the two components of the magnetic field, and to derive a distribution function for the magnetic field vectors.
The Distribution of Galaxies in Relation to Their Formation and Evolution
Authors: Peterson Bruce A.
Published: July 2016

The distribution of galaxies on the sky is not random, but has structure on a scale of ~ 30 Mpc. Similar structure in the cosmic background radiation is not present. Another expected source of structure in the background radiation is the finite size of the light horizon in the early Universe. The lack of observable structure in the background radiation implies extreme initial isotropy. Quantum effects may be responsible for this isotropy, and for the initial perturbations from which galaxies and clusters of galaxies formed.
The Early History of Our Galaxy: Dynamics
Authors: Freeman K. C.
Published: July 2016

Dynamical aspects of the early history of our Galaxy are discussed, with emphasis on the two-component nature of disk galaxies. Topics include the Eggen, Lynden-Bell and Sandage picture of the Galaxy's collapse, dynamical problems of the disk, and the bulge component.
The Distribution of Mass-to-Light Ratio With Radius in M31 and M33
Authors: Baldwin J. E.
Published: July 2016

New H I observations indicate that the mass-to-light ratios in the disks of M31 and M33 are independent of radius.
The Early History of Our Galaxy: Chemical Evolution
Authors: Peimbert Manuel
Published: July 2016

A general review is given of chemical abundance determinations; particular emphasis is given to abundances of galactic and extragalactic metal-poor objects since presumably they represent the abundances of the primeval material from which our Galaxy was formed. The following results are stressed: (a) most of the helium present in the galaxies of the local group as well as in other galaxies was produced before these objects were formed, (b) the heavy elements were produced mainly as the result of stellar evolution, (c) there is a chemical abundance gradient in our Galaxy and, by analogy with other galaxies, it is expected to be steeper near the nucleus, (d) the carbon and oxygen content of our Galaxy increased at a rate different from the metals, reaching their present abundance earlier than the other heavy elements, and (e) the increase of the iron abundance in the disk of our Galaxy with time has been small while that of carbon is negligible; furthermore, as a group the super-metal-rich stars correspond to the old disk population. Several models of galactic chemical evolution are reviewed.
Evidence for Non-Velocity Redshifts-New Evidence and Review
Authors: Arp Halton
Published: July 2016

Evidence for non-velocity redshifts in quasars and galaxies is reviewed. It is shown that all current statistical tests favour the association of at least some quasars with relatively nearby galaxies. It is shown that a statistically significant number of quasars falling close to faint galaxies have intermediate redshift (between z = 0.4 and 1.8). This confirms the previous result that those are the intrinsically most luminous quasars and keeps open the possibility that less luminous quasars can appear projected at large distances around very nearby galaxies.

It is shown that in four individual cases where quasars fall, projected, closest to bright galaxies, the galaxies show evidence of physical interaction. New evidence for perturbations of the inner isophotes of NGC 4319 by Markarian 205 and by a radio source on the opposite side is presented.

Evidence for systematically higher redshifts for compact and peculiar companion galaxies is reviewed. The intrinsic redshift-morphology relation for clusters of galaxies is commented upon and the relation to Tifft's work is noted. As a summarizing diagram, the individual associations of high redshift quasars and companions are used to show an empirical continuity of observed characteristics between compactness (taken to be a measure of youth) and excess redshift.

Finally some possible theoretical explanations for intrinsic redshifts are mentioned.
The Extragalactic Relative Distance Scale
Authors: Abell G. O.
Published: July 2016

Arguments are given to support the hypothesis that a characteristic point on a cluster luminosity function, m*, corresponds to the same absolute magnitude in all clusters, and thus is an appropriate standard candle for determination of relative cluster distances. It is shown, however, that if m*is a good standard candle, then the first and tenth brightest cluster galaxies, m(1) and m(10), respectively, are not, for m* – m(1) and m* – m(10) both differ significantly from cluster to cluster. Moreover, m(1) and especially m(10) depend on cluster richness. Distances derived from them for remote clusters chosen for analysis are thus subject to selection effects that depend on cluster richness and on Bautz-Morgan type. Finally, a procedure suggested by Bautz and Abell is described whereby m* can be estimated from observed properties of distant clusters.
Radio Frequency Observations of the Nuclei of Galaxies
Authors: Ekers R. D.
Published: July 2016

For spiral galaxies the nuclear radio emission is usually dominated by a complex distribution of emission with median diameter of 200 pc and median power of 1019 W Hz−1 sr−1 at 1400 MHz. There is a large range in both power and diameter. The power is independent of morphological type for the normal spirals but is correlated with the absolute optical magnitude and with the infrared emission. For Seyfert galaxies the emission is generally stronger, in some cases by several orders of magnitude (e.g. NGC 1275, 3C 120).

Elliptical galaxies have been found with very compact radio sources, some less than a parsec in diameter. These are as powerful as the strongest spirals (~ 1021 W Hz−1 sr−1). Even stronger compact nuclear sources are now being found in the nuclei of those elliptical galaxies which also have extended radio sources (the radio galaxies). The presence of nuclear sources of this strength is so highly correlated with the presence of extended sources that this suggests a continuing involvement of the nucleus.
Gravitational Interactions Between Galaxies
Authors: Toomre Alar
Published: July 2016

Recent theoretical studies of the consequences of fierce tidal interactions between galaxies are reviewed and compared.
The Magellanic Stream
Authors: Mathewson D. S. , Cleary M. N. , Murray J. D.
Published: July 2016

A southern sky survey of H I in the velocity range — 340 km s−1 to +380 km s−1 has shown that a long filament of H I extends from the Small Magellanic Cloud (SMC) region down to the South Galactic Pole and connects with the long H I filament discovered recently by Wannier and Wrixon (1972) and van Kuilenburg (1972). There is also some evidence that the feature continues on the other side of the Magellanic Clouds and crosses the galactic plane at l = 306°. The whole filament, which follows very closely a great circle over its entire 180° length, 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.
On the Growth Mechanism of Grains in a Primordial Stage of the Solar Nebula
Authors: Carusi A. , Coradini A. , Federico C. , Fulchignoni M. , Magni G.
Published: July 2016

Grain accretion processes in a protoplanetary nebula have been studied regarding: (a) the distribution function of grain velocities; (b) electrostatic and electromagnetic mechanisms between grains. The velocity distribution function has been investigated for grains embedded in a turbulent gaseous medium. Results have been obtained for protoplanetary nebula densities ranging from 10−19 to 10−10 g cm−3. Considering interactions between two grains, photoelectrically charged by galactic ultraviolet flux and by charged-particle capture, and solid-solid interactions (dipole fluctuation effect), the authors estimate the physical cross section σ(v) with respect to the geometric one σ0. Then a statistical approach for an assembly of grains gives the accretion or destruction rates for these small particles. Therefore, according to their characteristic velocities, the following processes have been studied: rupture, fusion, vaporization.
The Escape of Planetary Atmospheres
Authors: Menzel Donald H.
Published: July 2016

The problem of escape of atmospheres from the Moon and planets has roots deep in ancient history. Many of the great philosophers of the past regarded the Earth's atmosphere as a medium extending to infinity, with a stationary Earth imbedded at the center. Indeed, it was this concept that led Ptolemy, among many others, to conclude that the Earth could not be moving, for otherwise it would be subject to a gale-force wind caused by its own motion. This idea fostered many of the early stories of interplanetary visitations. Lucian, for example, writing in the second century A.D., has his Icarome nippus fly to the Moon and beyond by means of wings attached to his body.
Optical Properties of Particles in Planetary Atmospheres: Laboratory Studies
Authors: Williams Dudley
Published: July 2016

The laboratory techniques employed for the determination of optical constants are discussed briefly. The values obtained for the real n and imaginary k (or ni) parts of the refractive indices of water, ice, and liquid ammonia are presented graphically. Work currently in progress on solid ammonia and on sulphuric acid is discussed. Other approaches to studies of the properties of aerosols in planetary atmospheres are presented briefly.
Infrared Spectra of Venus
Authors: Young Louise Gray
Published: July 2016

A historical account of observations of Venus and their interpretation is given. The major constituent of the atmosphere on Venus (CO2) was detected spectroscopically forty years ago, and minor constituents (CO, HF, HCl) have been found more recently. The infrared spectra also provide a means of studying the motions of her cloudy atmosphere. The composition of the clouds has been sought in the reflection spectrum of Venus, and some of the evidence for their nature is discussed.
Radio Interferometry of Venus at Short Wavelengths
Authors: Janssen Michael A.
Published: July 2016

From short wavelength (γ < 4 cm) interferometry of Venus interpreted on the basis of the physical structure and bulk composition of its atmosphere as given by spacecraft measurements, evidence for the presence of a source of opacity in addition to CO2 is found. This opacity presumably is due to unknown minor constituents of the atmosphere of Venus.
Profondeur de penetration et formation des raies dans une atmosphere diffusante
Authors: Fouquart Y.
Published: July 2016

The systematic study of the distribution of the photon optical path in a finite scattering atmosphere gives the penetration depth of the radiation in a cloud; one can get then an accurate knowledge about the layer thickness in which the spectral line has been formed. The relation between the observed line frequency and the corresponding altitude is thus precisely expressed. The method is presented here with some preliminary results, it could be applied to the Venus, Jupiter and Saturne atmospheres to improve the knowledge of their clouds internal structure.

Using this method in case of Venus spectral lines it has been possible to deduce that for the Hansen's model, the optical depth of Venus clouds should be of the order of 40 and the cloud top closed to 70 km height.
Etude theorique de la repartition de luminance sur le disque de Venus
Authors: Bigourd C. , Deuze J. L. , Devaux C. , Herman M. , Lenoble J.
Published: July 2016

The analysis of the sunlight scattered by Venus gives some insight upon its clouds. The measurements of polarized light are probably more sensitive to the nature of their constituents, and some recent studies seem to be able to give a satisfactory interpretation of this part of the scattered light. But the polarized light concerns the upper part of the clouds, and it is interesting to compare these results with intensity measurements. The phase curves, for the integrated light, leave some indeterminations, so we have studied if the intensity distribution on the Venus disk could give more accurate informations. This work, based on some plates kindly communicated by A. Dollfus, and analysed at Meudon Observatory, is more a preliminary investigation of the sensitivity of the method than an interpretation of the partial results presented. A simple model, of homogeneous plane parallel cloud, has been used, and the influence of various parameters has been tested (single scattering albedo, refractive index of particles and size distribution, optical depth of the cloud).
Results of Current Mars Studies at the IAU Planetary Research Center
Authors: Baum William A.
Published: July 2016

The purpose of this paper is to give an updated report on several recent findings concerning Mars obtained from studies now in progress at the Planetary Research Center of Lowell Observatory. In this work, extensive use has been made of ground-based images obtained almost hourly by seven observatories cooperating under the International Planetary Patrol Program (Baum, 1973).
Photometric Data from Some Photographs of Mars Obtained with the Automatic Interplanetary Station ‘Mars 3’
Authors: Botvinova V. V. , Bugaenko O. I. , Koval I. K. , Narajeva M. K. , Selivanov A. S.
Published: July 2016

The results of detailed photometric treatment of Mars photographs obtained with the Automatic Interplanetary Station ‘Mars 3’ in three wavelengths are given. Photometric maps of the Martian surface have been constructed; a thin layer observed near the limb has been investigated.
Mars: Local Structure of Dust Storms
Authors: Barenblatt G. I. , Golitsyn G. S.
Published: July 2016

A hydronamical theory describing the motion of the dusty flow including the effects of thermal stratification is presented. It is shown that the dust, while decreasing the intensity of turbulence in the flow, can accelerate the wind. Applied to Mars, the theory reveals that these effects may be important there in understanding the nature and the long duration of Martian dust storms.
The Influence of the Surface Boundary Layer on Evolutionary Models of Jupiter
Authors: Graboske Harold C.
Published: July 2016

A recent theoretical study of the structure and evolution of Jupiter (Graboske et al., 1974b) is based on a three-stage model of Jovian evolution. The central phase, gravitational contraction of an adiabatic, homogeneous convective fluid system, begins early in solar system evolution and lasts for times of the order of 2 × 109 yr. Good agreement with observed radius and luminosity is achieved for a model with a solar mixture composition. The surface boundary layer has a dominant influence on the evolutionary timescale. Surface boundary factors which are important are the solar energy input, a function of the solar luminosity and the planetary albedo, and the detailed physics of the superadiabatic zone, which depends on the variation of opacity and ∇ad with depth. The evolutionary study demonstrates that the current planet cannot be an adiabatic homogeneous fluid throughout. The inclusion of a superadiabatic zone is necessary, and the existence of a heterogeneous (gravitationally layered) fluid interior is possible.
Atmospheric Properties of Jupiter Determined from Galilean Satellite Eclipse Light Curves
Authors: Shorthill R. W. , Greene T. F. , Smith D. W.
Published: July 2016

Twelve eclipse light curves for the Galilean satellites have been observed at 30 colors. The shape of the curves depend upon Jovian atmospheric properties such as Rayleigh scattering, aerosol distribution, molecular absorption, scale height and cloud top altitude, as well as the satellite diameter. Different zenographic latitudes and longitudes along the sunrise and sunset terminator have been observed. Very long absorption path lengths are obtained compared to normal incidence because of the tangential passage of the Sun's rays. Refractive tails are observed in most cases which allow aerosol distributions to be determined. The other atmospheric properties may also be derived.
Millisecond Polarized Pulses in Decametre-Wave Radiation from Jupiter and Sun
Authors: Barrow C. H.
Published: July 2016

A new approach is suggested to the problem of the theory of Jovian decametric radiation and physical conditions at the point of origin. This depends upon a comparison of the characteristics of fast pulse decametre-wave radio emission from both Jupiter and the Sun and invokes the deductive procedure which Sagan (1971) has called ‘Propositional Calculus’.

Fast polarized pulses in radiation from Jupiter and the Sun have been studied at fixed frequencies in the range 18 to 26 MHz with time resolutions from one to five msec; a number of similarities between the pulses from both sources have been noted. A comparison of some of the pulse characteristics is being made in order to decide whether or not they are sufficiently alike to be regarded as having a common mechanism of origin at both Jupiter and the Sun. From this ‘decision’ it is proposed to establish boundary conditions for theoretical study. Fast pulses in the Jupiter radiation are generally supposed to be a source phenomenon although their actual mechanism is not understood. The reasons for this are to some extent inferred rather than proven and so, to check the possible (if unlikely) role of the interplanetary medium, observations are also being made using the large 26 MHz array at the University of Florida to search for possible fast pulses in the radiation from the more distant source Taurus A.
Photopolarimetry of Planets
Authors: Gehrels T.
Published: July 2016

Polarimetry is reviewed in a new book of which I am the editor (Gehrels 1974) while detailed papers of our group in Arizona continue to appear in a series ‘The Wavelength Dependence of Polarization’ in the Astronomical Journal.
On rotating ring orbits in galaxies
Authors: Lindblad Bertil , Lindblad Per Olof
Published: July 2016

If ω is the angular velocity of circular motions in a stellar system depending on the distance R from the centre, and κ is the frequency of oscillation in the radius vector for an orbit in the equatorial plane which differs slightly from a circular orbit, we may show that in a coordinate system of angular speed
the orbit in question is a closed oval, in the first approximation an ellipse, with two opposite vertices and with its centre in the centre of the system. The conditions are illustrated in Fig. 1, when AA is the apsidal line of an orbit. The expression for κ is
where A is Oort's constant of differential rotation. If the distribution of matter in the stellar system may be approximated by a sum of concentric spheroids with one and the same plane of symmetry, the density increasing with decreasing dimensions of the spheroids, we should expect κ = 2ω close to the centre, whereas in the outermost regions we must expect that κ approaches to ω. It is therefore likely that ω – ½κ does not change appreciably within the system. Fig. 2 gives the run of κ, ω, and ω – ½κ for the galactic system according to the values of ω given by Kwee, Muller, and Westerhout [2]. In this case ω – ½κ changes very slowly with R. A relative orbit has a quite important property, if ω – ½κ is constant in the interval of R covered by the orbit. In this case, if the centre of gravity of a cloud of free particles follows the orbit, and if the velocity dispersion is small, the particles will pursue orbits which differ only slightly from each other and from the central orbit, but on the other hand there will in general be considerable differential motions along the central orbit. This orbit is therefore the curve in space along which a cloud of free particles tends to disperse. The process is similar to the dispersion of the meteoric particles of a comet along its orbit.
On Microwave Recombination Lines from Hi Regions
Authors: Zuckerman B. , Ball John A.
Published: July 2016

There has been considerable uncertainty in the nature of the regions from which carbon and narrow hydrogen lines have been observed. Specifically there are two different models. In model I the lines originate in low-density Hiregions that are basically atomic, and stimulated emission enhances the line intensity by an order of magnitude. In model II the lines originate in the outer layers of very dense molecular regions and are due primarily to spontaneous emission. The first model is generally accepted and used by the astronomical community. However, we believe that the second is correct.
Interstellar Molecules – Theory
Authors: Brown R. D.
Published: July 2016

A number of possible mechanisms for the formation of molecules in the interstellar medium are discussed. Plausible suggestions have been made for the production of most of the known diatomics, but there is little understanding of polyatomics so far.
Galactic Background Radiation at 2 cm and Thermal Electrons in the Galaxy
Authors: Hirabayashi H.
Published: July 2016

The galactic background radiation at 4.2 and 15.5 GHz was observed with a resolution of 11′ at nine points on the galactic equator free of confusion from discrete sources. Relative amounts of thermal and nonthermal radiation were determined, and conditions in the interstellar gas are discussed.
Thermal and Maser Phenomena in Rotationally Excited Oh
Authors: Palmer Patrick
Published: July 2016

Both maser emission and thermal emission and absorption have been observed from the rotationally excited 2π3/2, J = 5/2 and 2π1/2, J = 1/2 states of OH. Conditions in the interstellar gas are discussed.
Magnetic Fields in OH Maser Clouds
Authors: Davies R. D.
Published: July 2016

Observations of Class I OH maser sources show a range of features which are predicted on the basis of Zeeman splitting in a source magnetic field. Magnetic field strengths of 2 to 7 mG are derived for eight OH maser sources. The fields in all the clouds are directed in the sense of galactic rotation. A model of W3 OH is proposed which incorporates the magnetic field data. It is shown that no large amount of magnetic flux or angular momentum has been lost since the condensation from the interstellar medium began.
On the First Southern-Sky H2O Masers Observed at Itapetinga, Brazil
Authors: Kaufmann Pierre , Fogarty W. G. , Scalise E. , Schaal R. E.
Published: July 2016

The first spectra of southern H2O masers obtained with the 14-m Itapetinga radio telescope are described. A new H2O source was found in H2-3 (G345.4 − 0.9).
Hii Regions: Some the Oretical Developments
Authors: Kahn F. D.
Published: July 2016

Observations have revealed the presence of inhomogeneities in both density and velocity in Hiiregions. Dense non-ionized condensations can persist for a long time, developing bright rims of dense ionized gas around them. Attempts have been made to understand the large ~50 km s-1motions seen in some Hiiregions by invoking stellar winds or the flow of cosmic ray particles through the plasma.
Radio Observations of IR/OH/H2O Stars
Authors: Caswell J. L.
Published: July 2016

A small percentage of infrared stars, selected on the basis of their IR brightness at 2.2 µm and their redness (I–K colour index), show 18 cm OH emission, and some exhibit 1.35 cm H2O emission; further investigations identify some of these objects as M-type supergiants and the remainder as M-type giant long-period variable stars.

For the strongest 1612 MHz OH emitters, long-baseline interferometry shows that the emission arises from a large number of small-diameter features distributed over a much larger, approximately elliptical region corresponding to a circumstellar cloud. Models for the geometry of the emitting regions are discussed.

The OH characteristics with respect to the ratios of line intensities for different transitions and the velocity structure are distinctive, not being found in other types of OH source; consequently a large number of new OH emitters can be recognized as probably IR/OH objects despite the absence of IR or optical data; the precise classification of these sources is considered together with their relevance in understanding the identified sources.
The Infrared Properties of Circumstellar OH/IR and H2O/IR Sources
Authors: Caswell J. L.
Published: July 2016

Anomalous OH and H2O microwave emission is a common occurrence in circumstellar shells surrounding cool oxygen-rich M supergiants and Mira variables. Infrared spectra have shown that the atmospheric conditions in these stars are such that the concentration of OH molecules is a maximum. For those with H20 microwave emission, strong H20 1.9 μm absorption is present.

There exists a growing number of typical OH/IR sources discovered by radio surveys, for which no associated IR object has yet been found. Preliminary results of TV photography to discover IR counterparts are shown.

Several interesting correlations have been defined between the IR colour, period and amplitude of infrared variability, and the velocity separation of the OH emission peaks. The relationship of these to pulsationally driven mass loss and the observed characteristics of circumstellar dust shells is investigated.

The maser emission from OH/IR and H20 / I R sources is believed to be pumped by IR radiation. Combined studies of the variability of OH and H20 emission and the IR continuum of the Mira sources confirm that IR pumping is probably the dominant mechanism, although the data do not appear to favour any specific pump scheme. The OH masers are at least partially saturated; the degree of saturation of the H20 masers is unclear.
Occultation Observations of the Galactic Center Region at 327 MHz
Authors: Swarup G. , Gopal-Krishna  , Sarma N. V. G.
Published: July 2016

Lunar occultation observations of the thermal sources Sgr B2, G0.9 + 0.1 and G1.1-0.1 at 327 MHz have been used to estimate their electron densities and temperatures. A new nonthermal source of size ∼ 10 × 5′ has been found about 7′ to the south of G1.1 − 0.1. A brightness contour diagram with a resolution of approximately 25 × 6′ is presented for the background radio emission near the sources Sgr A and Sgr B2.
Current Problems in 21 cm Line Studies of the Large-Scale Structure of the Galaxy
Authors: Burton W. B.
Published: July 2016

A number of current problems in 21 cm line studies of the Galaxy as a whole are discussed. Because of the difficulties involved with straightforward mapping, it is important to isolate integrated and other properties of the hydrogen profiles, the interpretation of which does not require accurate distance determinations. In addition, methods of analysis are necessary which either account for or exploit the sensitivity of hydrogen profiles to velocity irregularities and to geometrical configurations. The model-fitting approach to the interpretation of the hydrogen profiles is useful in this respect. Extragalactic hydrogen studies which show the relative ordering of the various components of spiral structure can inspire research in our own Galaxy. Such investigations are necessary for an understanding of the forces governing the spiral structure. It seems that the neutral hydrogen is primarily a tracer of locations where the overall distribution of stars is producing a gravitational sink. Other spiral tracers, in particular the molecules, are better considered as tracers of regions where the gas has been compressed, perhaps (at least on a large scale) by the shock front predicted by the density-wave theory.
Continuum Radio Emission and Galactic Structure
Authors: Price R. M.
Published: July 2016

Recent studies of high latitude brightness have shown that in several regions a significant proportion of it is due to loop features. The largest of these are now thought to be local (within a few hundred parsecs) and perhaps to be due to supernova events.

Aperture synthesis maps of 45 external spiral galaxies have shown large-scale continuum nonthermal features in the disks of some and, in general, an absence of spherical halos around the galaxies. This supports the view that the radio emission from our Galaxy can best be described as coming from a thick disk. Any large-scale spherical component could not have a volume emissivity greater than 1.5% of the average volume emissivity of the disk at meter wavelengths.

A comparison of the disk radiation with new disk models suggests that the galactic plane radiation has two components: a base disk and a spiral component. Each of these contributes ~50% of the total power output of the disk at 150 MHz.
The Bonn 408 MHz Survey
Authors: Haslam C. G. T. , Wilson W. E. , Graham D. A. , Hunt G. C.
Published: July 2016

The 100 m telescope was used to complete the northern sky survey started at Jodrell Bank. The survey aimed at reaching the confusion limit of the telescope. Zero levels are consistent within ± 3 K, and scale errors are less than 10%. The survey will be published in the form of maps; a machine readable version is also available.
Large Scale Emission from Radio Galaxies
Authors: Andernach H. , Wielebinski R.
Published: July 2016

Radio galaxies are known to exhibit a variety of scales in their structure. First we have the nuclear sources, which so far have not been completely resolved even on the scale of 1/10 milliarcsecond with VLBI observing methods (e.g. Preuss, 1981). Then we have the ‘jets’ (which at some stage break up into ‘blobs’) which are considered to transfer energy from the ‘nuclear engine’ to the outer heads. The latter appear to be the sites of transfer of the collimated jet energy into a diffuse emission region. Despite their usually low brightness these diffuse emission regions dominate the internal energy content in particles and fields, even for the collimated doubles. Note that only 1% of the total energy in Cyg A is in the hot spots (Perola, 1981).
The Spectral Index Distribution of Cygnus A
Authors: Scott P. F.
Published: July 2016

High dynamic range maps of Cygnus A at 2.7 and 5 GHz have been used to investigate the variation of spectral index over the extended parts of the source. Although both components show a steepening of spectral index away from the hotspots there is a marked asymmetry between the two components. This is interpreted as being due to a higher value of magnetic field in the Sf component.
Nuclear Ejection — One Side at a Time
Authors: Rudnick Lawrence
Published: July 2016

Examination of the structures of extragalactic radio sources shows a distinct asymmetry in addition to the more general symmetries which are well known. The most likely explanation for the observed asymmetries is that ejection from the active nucleus occurs in only one direction at a time. This direction then switches back and forth to form the large scale double structures. Implications of this picture for the nuclear engine and the radio source environment are discussed.
Extended Optical Line Emission Associated with Radio Galaxies
Authors: van Breugel Wil , Heckman Tim
Published: July 2016

Using the Video Camera (e.g. Butcher et al. 1980) and the High Gain Video Spectrometer (e.g. Heckman et al. 1981) we are carrying out a program at Kitt Peak to search for optical line emission associated with the jets and lobes of radio galaxies. Several sources have been found in which extended optical line emission is clearly related to the non-thermal radio emission. Some general information on these and a few other sources is summarized in Table 1.
Radio-Optical Studies of a Complete Sample of Abell Clusters
Authors: Mills B. Y. , Hunstead R. W.
Published: July 2016

Study of the properties of radio galaxies in clusters is beset with problems of selection and identification. To reduce these problems we have selected a complete sample of Abell clusters and are using optical spectra of identified galaxies to determine their cluster membership. The sample is in a volume of space defined by the limits of coverage and sensitivity of the two Sydney University radiotelescopes and the Anglo-Australian Telescope; it comprises the 42 clusters with δ≤-8° and distance class 4 or closer. Radio maps have been prepared using archive 408 MHz data from the Molonglo Cross. Possible optical identifications have been selected from the Palomar Sky Survey and low-dispersion optical spectra have been taken of these and sometimes other galaxies or stellar objects within the cluster area. When needed, maps of the cluster areas have been produced at 1415 MHz using the Fleurs Synthesis Telescope. Some details of our early results have been published (Mills et al. 1978, 1979) and here a brief summary of the overall statistics is presented. Observations on five clusters remain to be completed but should not greatly affect the present conclusions.
The Radio Emission of Interacting Galaxies
Authors: Hummel E. , van der Hulst J. M. , van Gorkom J. H. , Kotanyi C. G.
Published: July 2016

Gravitational interaction is a straightforward interpretation of some of the peculiar optical morphologies shown by galaxies. There have also been attempts to study the effects of a gravitational interaction on the radio continuum emission. Statistically, the central radio sources (inner 1 kpc) in interacting spiral galaxies are about three times stronger than in isolated spirals; on the other hand, the intensity of the extended emission does not seem to be affected (Stocke, 1978; Hummel, 1981). Peculiar radio morphologies are not a general property of interacting galaxies, since in the complete sample studied by Hummel (1981) of spirals with a probability ≥0.8 of being physically related to their companion, less than 5% have a peculiar radio morphology.
Radio and X-Ray Structure of Centaurus A
Authors: Feigelson Eric D.
Published: July 2016

Recent studies of the nearby radio galaxy Centaurus A with the Very Large Array and the Einstein X-Ray Observatory reveal complex radio and X-ray structures. A prominent one-sided jet comprised of resolved knots located 0.2–6 kpc from the nucleus is seen in both radio and X-rays. The X-ray emission is probably synchrotron, requiring in situ reacceleration up to Γ ≃ 107. Inverse Compton emission is not a likely explanation though a thermal model in which the nucleus ejects dense 105M0 clouds cannot be excluded. An elongated X-ray region is also found near the “middle” radio lobe and optical HII regions ∼ 30 kpc NE of the nucleus. Conditions around the active nucleus, the absence of X-rays from the inner radio lobes, and X-ray evidence for a hot interstellar medium are briefly discussed.
Relativistic Beaming and Quasar Statistics
Authors: Browne I.W.A. , Orr M.J.L.
Published: July 2016

The predictions of a scheme which attributes the observed differences between flat and steep spectrum quasars to projection and the effects of relativistic beaming are explored. We conclude that the statistical properties of quasars are entirely consistent with such a scheme provided the mean Lorentz factor in the central components of quasars is ∼5.
Highly Polarized Emission from the E-Hotspot in DA240
Authors: Tsien S. C. , Saunders Richard
Published: July 2016

The hotspot in the eastern lobe of the nearby giant radio galaxy DA240 (z=0.0356) provides a rare opportunity to examine the detailed polarization structure of a hotspot. Maps have been made with the Cambridge 5-km telescope at 2.7 and 5.0 GHz. The 5.0-GHz maps are shown in Figs 1 and 2. The main characteristics are: (a) The hotspot has an overall size in the 2.7-GHz map of 10×18 kpc2. It blends smoothly at its outer edge into the background of the extended lobe. The 5.0 GHz total intensity map shows a yet more compact region (subcomponent A). It has not been fully resolved in the direction of the minor axis and has a size <1×2.5 kpc2. There is a second much weaker and diffuse region (subcomponent B). Both subcomponents are superimposed on a broad plateau of emission. The hotspot has spectral index α(0.61–5.0)=0.52, minimum total energy Emin=3×1056 ergs and equipartition magnetic field Beq=2×10−5 G, values typical of other hotspots, although its projected distance from the nucleus is very large (0.65 Mpc);
Radio Emission from the Seyfert Galaxy NGC 5548
Authors: Ulvestad J. S. , Wilson A. S. , Wentzel D. G.
Published: July 2016

Weak radio emission from the type 1.5 Seyfert galaxy NGC 5548 has been mapped with high resolution at the VLA at both 1465 and 4885 MHz. The galaxy contains the largest (5.9 kpc) triple radio source known in a Seyfert galaxy. The central component of that triple is unresolved (<0.39×0.15 kpc) and has a flatter spectrum than the well-resolved outer lobes. In addition, the field surrounding NGC 5548 and two of the sources in that field have been mapped at 1465 MHz; the field sources are unlikely to be physically associated with NGC 5548.
Mechanisms for Jets
Authors: Rees Martin J.
Published: July 2016

The evidence is now compelling that “jets” delineate the channels along which power is supplied from galactic nuclei into extended radio sources — this accumulating evidence, reported by many speakers, has been one of the major themes of this conference. Jets (often apparently one-sided) have been discovered inside many symmetrical double sources. and M87, familiar optically as a “one-sided jet” for over 60 years, is now found to have weak double radio lobes. The VLA has resolved ∼ 70 jets in extended sources; there are now many instances where small jet-like structures are found on the VLBI scale; indirect arguments (some of which I'll mention) indicate that there is directed outflow on still smaller scales, and that the primary collimation may occur right down in the central “powerhouse” (scales ∼< 1015cm). The length-scales relevant to jet production and propagation thus span 9 orders of magnitude; the physical processes and conditions may vary widely over this vast range of scales. This paper will deal briefly with two aspects of jet physics: firstly, some direct inferences from radio maps; and, secondly, some possible mechanisms in galactic nuclei that could set up a collimated outflow.
Connections Between Turbulence and Jet Morphology
Authors: Benford Gregory
Published: July 2016

Radio jet morphologies may be caused by large-scale Kelvin-Helmholtz (KH) instabilities. If high-speed, pressure-confined fluid beams lie at the core of these jets, they are susceptible to KH modes, as studied by a number of authors.1–5 The “wiggles” seen, for example, in 3C449, NGC 6251, M87 and Cen A, may arise from helical instabilities.3,4 “Knots” may be radial oscillations (not necessarily unstable) forming sausage-like regions of compression, as in NGC 315, M87, Cen A etc. There seems no reason why such macroscopic modes should not appear. The smaller scale waves, however, cannot be easily resolved by radio astronomy, and can have profound effects, such as particle reacceleration. It would be rather more satisfying if there were observable large-scale implications of the microturbulence.
Infrared Observations of Radio Galaxies
Authors: Rieke George H.
Published: July 2016

For technical reasons, infrared studies of active galaxies have lagged far behind optical and radio ones. This is unfortunate, since entirely new aspects of these sources are often revealed in the infrared. The extreme efficiency of dust at degrading ultraviolet photons into cool thermal emission frequently makes the luminosity of an extragalactic source inaccessible to optical and radio astronomers. At the same time, the effects of dust on optical emission line ratios and continuum shapes can be profound. The complete identification of samples of radio sources will require infrared observations to supplement the optical techniques now generally employed, and the extreme properties of the sources bright in the infrared can provide new insights to conditions in extragalactic nonthermal sources. To illustrate these points, I will discuss three cases: 1.) galaxies undergoing a powerful burst of star formation, 2.) intermediate type Seyfert galaxies, and 3.) an extreme infrared identification of an extragalactic radio source.
A Search for HI in Elliptical Galaxies with Nuclear Radio Sources
Authors: Dressel L. L. , Bania T. M. , O'Connell R. W.
Published: July 2016

Many searches have been made in the last few years for 21 cm emission from neutral hydrogen in elliptical galaxies. Emission has been detected in several galaxies, which have 108 to 109 M⊙ of HI (for H○ = 100 km s−1Mpc−1). Upper limits between 106 and 109 M⊙ have been set for the HI mass in about 40 other galaxies. Why most E galaxies have so little gas, and why some few have detectable gas, remains a matter of great interest. Two of the galaxies with large HI mass, NGC 1052 and 4278, are known to have powerful nuclear continuum radio sources (P2380 ∼ 1022 WHz−1). Since both of these attributes are fairly rare among elliptical galaxies, their coexistence in these galaxies is not likely to have occurred by chance. We have therefore observed twelve other elliptical galaxies with nuclear radio power P2380 > 1022 WHz−1 at Arecibo Observatory, to determine whether a large mass of HI is a necessary auxillary to nuclear continuum emission.
Theoretical Models to Explain the Variable 21 cm Absorption Spectrum in AO 0235+164
Authors: Wolfe A. M.
Published: July 2016

The variability of the highly redshifted 21 cm absorption spectrum in AO 0235+164 presents us with two essential facts. First, rapid changes occur in the line depths of foreground clouds with redshift z ≃ 0.524. Second, the background radio source is among the most violently variable objects known. Thus it is reasonable to suppose that changes in the lines stem from activity in the background BL Lac object. The question is how?
Interstellar Scintillations as a Tool for Investigations of Hyperfine Structure in Extragalactic Radio Sources
Authors: Ozernoy L. M. , Shishov V. I.
Published: July 2016

Attempts to use interstellar scintillations (ISS) to study the fine angular structure of quasars and galactic nuclei have not yet met with any success. The main reason for this lies in the comparatively large angular size of the nuclear structure which has been investigated. If dependencies on wavelength for the scintillation index, flux and angular size of a source are taken into account (Ozernoy and Shishov, 1980), it appears that centimeter wave band rather than decimeter wave range used in previous work is most appropriate for observing ISS.
CM-Wavelength Fluxes and Polarizations of Compact Extra-Galactic X-Ray Sources
Authors: Aller Margo F. , Aller Hugh D. , Hodge Philip E.
Published: July 2016

Cm-wavelength observations of 15 BL Lac objects are presented. The degree of radio-wavelength variability is compared with the strength of the emission at optical and X-ray wavelengths.
Superluminal Expansion in 3C 179
Authors: Porcas R. W.
Published: July 2016

The detection of apparent faster-than-light motion (v=7.6c) in the core of 3C 179 poses some problems for the simple relativistic jet explanation.
Relativistic Jets as Radio and X-Ray Sources
Authors: Königl Arieh
Published: July 2016

Various predictions and implications of the relativistic-jet model for compact extragalactic sources are reviewed in the light of recent radio and X-ray observations.
Radio Observations of the Galactic Center
Authors: Backer D. C.
Published: July 2016

Low-resolution, radio-intensity maps of the Galactic Center are dominated by two structures: the extended, nonthermal region between ℓ = 0°.0 and 0°.3 called Sagittarius A(East); and the bright thermal source at ℓ = −0°.05 and b = −0°.05 called Sagittarius A(West). SgrA(East) is probably a supernova remnant. SgrA(West) is a dense, gaseous region which is the very center of our Galaxy. Within SgrA(West) is a pc-sized cluster of infrared sources — late-type stars and gas condensations — swirling about with a dispersion of 250 km s−1. The cluster contains a unique radio source with the following properties: a size not exceeding 1015 cm, a radio luminosity exceeding 1034 erg s−1, and rather stable properties on a time scale of 108 s. This compact, nonthermal object (SgrAcn below) may be surrounded by a 0.1pc infrared source. Models for SgrAcn include both 106 M⊙ black holes related to the central objects in radio galaxies and quasars (Oort 1977, van Buren 1978) and 1 M⊙ degenerate stars related to pulsars and X-ray binaries (Reynolds and McKee 1980). We present below the radio intensity spectrum as a basic datum for further development of either class of models.
Extragalactic Radio Supernovae in NGC 4321 and NGC 6946
Authors: Sramek R. A. , Weiler K. W. , van der Hulst J. M.
Published: July 2016

The supernovae SN1979c in NGC 4321 and SN1980k in NGC 6946 have both been detected at centimeter wavelengths at the VLA. The radio emission turns on very rapidly, but may be delayed by as much as a year with respect to the optical outburst. In both supernovae, the 20 cm radiation peaks after the 6 cm, and the radio emission has a very slow post-maximum decay.