bluuebunny/crossref_metadata_2025 huggingface dataset:
Substructures in the Narrow-Line Region of AGN
Authors: Veilleux Sylvain
Published: June 2019

The preliminary results of a high-resolution study of narrow emission-line profiles in bright Seyfert galaxies are reported. Profile substructures such as secondary peaks and shoulders are observed in nearly all the objects. The results of profile comparisons in Mrk 359, Mrk 533, and Mrk 1066 are briefly discussed.
Cloud Disruption and Formation
Authors: Palouš Jan
Published: June 2019

Star formation is responsible at least for a part of radiation coming from central regions of active galaxies. Violent bursts of star formation yield rapidly evolving massive stars, which transform in metal-rich enviroments into so called Warmers / Terlevich et al., 1987 / changing nebular spectra to Seyfert or Liner type.
Delayed Infrared Emission from Luminous Seyfert 1 Galaxies
Authors: Glass I. S.
Published: June 2019

Five Seyfert 1 galaxies of high absolute luminosity (ranging from 28 to 65 times that of NGC4151 at 3.5 μm) have been monitored since 1984 (or earlier) at JHK & L (1.25, 1.65, 2.2 & 3.5 μm). The results are shown in the accompanying figures. Where the variations were of sufficient amplitude, changes in L are seen to have been delayed ∼ 500 days compared to those at shorter wavelengths. In all cases, even in 3A 0557-383 where the amplitude of variation is small, each galaxy traces out loops with time if magnitudes at two different wavelengths are plotted against each other. The loops are always described in the same sense (clockwise as plotted here), such that variations at the longer wavelengths are seen to be retarded compared to those at the shorter. Plots of this kind appear to be a sensitive way to detect delays even when the data are too sparse to support a credible cross-correlation.
Megamasers in Young Active Galactic Nuclei
Authors: Baan Willem A.
Published: June 2019

Megamaser emission provides new insights into the physics of active galactic nuclei. The megamaser phenomenon is consistent with a low-gain amplification model, where inverted foreground molecules amplify the radio continuum from the nucleus. The molecular gas seen in emission in the megamaser galaxies is located between 50 and 300 parsecs from the nucleus covering part of a possible NLR. Megamasers have been found for the molecules OH, H2CO and H2O. However, only OH megamasers form a clearly identifiable group of galaxies. They occur in prominent FIR galaxies and the FIR radiation field serves as a pumping agent for the OH molecules (Baan 1988). As a result only the ground state lines of OH are in emission, while the lines from excited states are in absorption (see Henkel, Güsten and Baan 1987).
Relationships of the Active Nucleus, Galaxy, and Environment
Authors: Fricke K. J. , Kollatschny W.
Published: June 2019

35 years ago Baade and Minkowski (1954) suggested that a galaxy collision - diagnosed from the peculiar appearance of the parent object and its strong emission lines - is responsible for the strong radio-source CygA. This was the first time that gravitational interactions between galaxies were suggested to trigger nuclear activity. Over the following decades after the detection of the quasars and the gradual realization that quasars, comparable to the Seyfert phenomenon, are events at the nuclei of seemingly isolated galaxies, the collision hypothesis was abandoned. Efforts concentrated on the understanding of the activity as internal processes in the host galaxies, possibly aided by infall of gas from the intergalactic medium (cf. Rees, 1978; Gunn, 1979).
Activity of Interacting Galaxies Mkn 673: A Close-By “E+A” Galaxy
Authors: Kollatschny W. , Fricke K. J.
Published: June 2019

The close-by double nucleus galaxy Mkn 673 shows spectra and colors which are typical for “E+A” cluster galaxies.
Nuclear Starbursts in Barred Spirals
Authors: Devereux N.A.
Published: June 2019

The first analysis of the Infrared Astronomical Satellite (IRAS) data revealed differences between barred and unbarred spirals. The study of Shapley-Ames galaxies, by De Jong et al (1984), revealed that barred spirals tend, on average, to be associated with “warmer” far infrared color temperatures and higher Lfir/Lblue ratios than unbarred spirals. In a related study Hawarden et al (1986) noted that barred and unbarred spirals could be partially segregated on the basis of the IRAS S25μm/S25μm flux ratio. Both sets of investigators attributed the differences, between barred and unbarred spirals, to a nuclear starburst in the barred types.
Physical Properties of the Extranuclear Emitting Regions in Irregular and Interacting AGNs
Authors: Rafanelli P.
Published: June 2019

CCD slit spectra have been obtained at Lick Observatory of a sample of fourteen close interacting and irregular Seyfert galaxies. The spectra of the extranuclear emitting regions have been investigated and classified using the quantitative criteria recommended by Veilleux and Osterbrock to distinguish objects photoionized by thermal sources from objects photoionized by a “power law” continuum. From our data it results that four out of the twenty emitting regions identified are typical H II regions, while eight have spectra photoionized by a hard-photon spectrum. Seven regions show a twofold behavior which is interpreted in terms of a combination of photoionization, shock heating and scattering of light by dust.
Far-Infrared Properties of Markarian Galaxies with Multiple Nuclei
Authors: Mazzarella J. M. , Bothun G. D.
Published: June 2019

We have coadded the IRAS data on a sample of 188 multiple-nucleus and morphologically peculiar Markarian galaxies noted as “interacting” in the compilation of Mazzarella and Balzano (1986). We have increased the number of objects in this sample with 60μm and 100μm IRAS detections by a factor of two from what is available in the Point Source Catalog, allowing the determination of far-infrared (FIR) luminosities and colors for over 130 morphologically peculiar Markarian galaxies. The galaxies in this sample have diameters less than 2′, and thus were seen as point sources by IRAS. All far-infrared properties discussed here apply to the entire multiple-nucleus or peculiar system. These data provide a unique opportunity to study the far-infrared properties of mergers which have prior indications of starburst or Seyfert activity as evidenced by their ultraviolet excess.
Low-Activity Nuclei in Spiral Galaxies
Authors: Fabbiano G.
Published: June 2019

Two types of active nuclei have been observed in normal spiral galaxies in X-rays with the Einstein Observatory: low-activity AGN, and starburst regions. The prototype of the first kind is the nucleus of M81 (Elvis and Van Speybroeck 1982; Fabbiano 1988a), but similar nuclei might also be those of M33 and NGC 1313. Soft X-ray spectra of these nuclei suggest relatively steep soft X-ray components (Trinchieri, Fabbiano and Peres 1988; Fabbiano and Trinchieri 1987; Fabbiano 1988a), reminiscent of those observed in QSOs by Bechtold et al (1987) and Wilkes and Elvis (1987). In M81, in particular, this soft component might supply enough photons to explain the optical line spectrum. If this soft X-ray component originates from an accretion disk surrounding a central black hole, the mass of the latter is likely to be smaller than 104–5 solar masses.
The Milliarcsecond Structure of Active Galactic Nuclei Observed with VLBI
Authors: Pearson T. J. , Readhead A. C. S.
Published: June 2019

Very Long Baseline Interferometry at radio wavelengths is the only technique available for imaging the central few parsecs of powerful radio galaxies and quasars. VLBI observations have shown that in many nuclei radio-emitting material is collimated into a jet on a scale less than a parsec and ejected at relativistic velocities. The interpretation of the observations is complicated by the relativistic motion, however: the images are dominated by those parts of the source that are moving almost directly towards the observer, and thus amplified by relativistic aberration. Nonetheless, the VLBI images are vital for understanding the nature of the central engine, the cause of the collimation, and the physics of the jets.
Radio Observations of Moderately Compact Steep Spectrum Sources
Authors: Akujor Chidi , Browne I.W.A. , Wilkinson P.N.
Published: June 2019

It is now common practice for objects with a steep radio spectrum and compact radio structure to be lumped together and called compact steep spectrum (CSS) sources (Peacock and Wall, 1982; van Breugel, 1984 Fanti et al. 1985). This rather arbitrary categorisation results in the class containing sources with a wide range of structures, from core-jet or complex (e.g. 3C147,3C48), small classical doubles (e.g. 3C237, 3C241), to VLBI compact doubles (e.g. CTD93; Phillips and Mutel, 1982). Some of the questions we are asking include:

(a)

Are compact sources intrinsically small, or do they appear small because they are seen in projection?

(b)

Why are structures in compact radio galaxies and compact radio quasars different? Wilkinson et al. (1984) and Spencer et al (1988, in preparation)have shown that there appears to be a ‘clear-cut’ difference in morphology between quasar CSS and galaxy CSS, with quasars showing more distortions while galaxies tend to be doubles. But is this trend present even in their slightly more-extended counterparts?
Protoplanetary Material Around Nearby Stars
Authors: Aumann Hartmut H.
Published: June 2019

A statistical analysis of IRAS observations indicates that about 20% of the nearby main sequence stars, and probably a similar fraction of main sequence stars not detectable by IRAS, shows evidence of significant infrared excess beyond 12 microns. Spectral type A dwarfs are predominant, but not exclusive in showing large 60 micron excesses. Our solar system, when viewed from sufficient distance, appears to have, in contrast to this, less than 1% of cool infrared excess. These observational facts are consistent with the working hypothesis that cold infrared excess in stable main sequence stars is due to proto-planetary material, observable during the accretion phase in the evolution of a solar system.
Evidence for a Solar Companion Star
Authors: Muller Richard A.
Published: June 2019

Periodicity seen in both the mass extinctions and large impact cratering on earth can be explained if one postulates that the sun has a companion star, orbiting in a moderately eccentric orbit with a major axis of 2.8 light-years. No other explanations that have been suggested are compatible with known facts of physics and astronomy. If the companion is a red dwarf star, the most common kind in the galaxy, then no previous astronomical observations would have found it. A search for red objects with large parallax is now underway at Berkeley, and has a good chance of identifying the star in the near future.
On the Occurrence and Appearance of Galactic Life Forms: A Thermodynamic Approach
Authors: Bodifee G. , de Loore C.
Published: June 2019

Biological life is an evolving complex dissipative structure, in the sense introduced by Prigogine. The question is considered how life in an advanced stage of evolution manifests itself to an outside observer. Fundamental uncertainties are inherent to the process of self-organization as manifested by dissipative structures. Their evolution is determined by stochastic fluctuations in far from equilibrium conditions, where instabilities arise that cause bifurcations in the behavior of the process system. Since no specific physical or chemical properties of extraterrestrial life can be predicted, general characteristics based on fundamental thermodynamic principles should guide us in our SETI programs. A biological system necessarily must be macroscopic, open with regard of the rest of the universe, and far from thermodynamic equilibrium. The processes within the system must be strongly nonlinear. We should therefore look for life in environments that are in a staticnary far from equilibrium state, such as planetary surfaces and cool interstellar molecular clouds, where an extreme nonequilibrium exists between radiation and kinetic temperature. In any case an advanced form of life should manifest itself by a large entropy emission, possibly carried by low-grade energy radiation, and propably not by information-rich communication channels intended for internal process regulation.
The Multichannel Spectrum Analyzer
Authors: Peterson A. M. , Chen K. S. , Linscott I. R.
Published: June 2019

The MCSA is a special-purpose digital signal processor. Its main function is to filter a wide-band signal into many narrower bands, so that each of the output bands has a bandwidth that is a better match to the signal being searched for.

The basic MCSA provides simultaneous output bandwidths of approximately 1 HZ, 32 Hz, 1024 Hz, and 74 kHz over a spectrum that is about 8 MHz wide. The input to the MCSA consists of a complex signal sampled at 10 MHz, and the outputs consist of either complex samples or power (square-law-detected) samples. In addition, the MCSA provides an accumulator for taking the integral of the power of the output bands for periods up to 1000 sec.

The MCSA hardware is constructed using wire-wrap technology. The implementation of the hardware is done with the aid of a computer program developed specifically for the design of the MCSA. Care has been taken in the MCSA design to ensure that engineering tradeoffs do not adversely affect the performance of the system.
Software Implementation of Detection Algorithms for the MCSA
Authors: Cullers D. Kent
Published: June 2019

The NASA Multichannel Spectrum Analyzer (MCSA) supplies data in several formats and in a wide range of frequency resolutions. To decide if an extraterrestrial signal is present, this data is searched using detection algorithms particularly sensitive to signals concentrated in frequency and/or time. The algorithms, whose ultimate sensitivities are determined by theoretical considerations, are also constrained by available computing power. At present, practical detection of repetitive pulses is possible at an average power about five times lower than that for incoherent CW detection. After a period of field testing, the best detection algorithms, presently implemented in software, will be converted to hardware to increase their speed.
Questionmarks Remaining
Authors: Marx George
Published: June 2019

As this successful Symposium is drawing to a close, let me bring to your attention some important questionmarks that still remain unanswered and for which we will hopefully have some better answers in our next meeting in Hungary in the summer of 1987.
Observed Surface Densities in Globular Clusters
Authors: King Ivan R.
Published: June 2019

This review of observations is oriented toward the problem of core collapse in globular clusters. After a brief discussion of methods of determining surface densities, recent results are cited which show that the central brightness peak seen in M15 also appears in several other clusters. The central peaks of brightness are interpreted as the result of core collapse, which theories have repeatedly predicted. If binaries stabilize the collapsed core, the cluster should follow a Hénon model. In two of the three cases tested this model is a reasonable fit. Remaining theoretical questions are listed, as are observational needs.
A High Spatial Resolution Investigation of the Core of Some Dynamically Evolved Globular Clusters
Authors: Aurière M. , Cordoni J. P. , Le Fèvre O. , Terzan A.
Published: June 2019

We present a high spatial resolution photographic study of the core of some concentrated globular clusters (F.W.H.M. of averaged star intensity profiles reaches 0″.5 on the best plates). Good plates of M 79, M 53, M 3, M 5, M 13, M 92, NGC 6397, M 15, M 2 and M 30 were obtained (Aurière and Cordoni, 1983, Astron. Astrophys. Suppl. Ser. 52, 383 and references therein). The observations are mainly obtained at the 2 m and 1 m Cassegrain telescopes of Pic-du-Midi Observatory. The high spatial resolution of our plates enables us to achieve stellar photometry, at least for the bright stars, in these overcrowded regions. Surface photometry is also obtained.
A Statistical Treatment of Low-N Systems
Authors: Casertano Stefano
Published: June 2019

The long-term evolution of N-body systems with high N (>104) cannot yet be studied by direct integration of the equations of motion. Instead, the study of systems with smaller N can give insight into the higher N limit in two ways. First, we can measure the dependence on N of all quantities of interest for a range of N-values, and extrapolate the results to higher N. Second, even a very high-N system will eventually undergo core collapse, at which point the central dynamics will be dominated by a subset of stars with small N (10–100).
3-Integral Models for Globular Clusters
Authors: Lupton Robert
Published: June 2019

This work was done in collaboration with Jim Gunn.
Dynamics of Open Star Clusters
Authors: Wielen Roland
Published: June 2019

The dynamical evolution of open star clusters has been studied successfully by numerical N-body simulations. We compare in detail the theoretically predicted lifetimes with those derived from the observed age distribution of open clusters. Rare but efficient encounters between clusters and giant molecular clouds are probably responsible for the sudden disruption of many open clusters. Massive black holes from the galactic corona would, on the average, affect only old open clusters.
Some Summary Remarks
Authors: Ostriker Jeremiah P.
Published: June 2019

Of the classical problems of physics there is one which might be picked out as simplest to state but slowest to approach solution. “What is the fate of a self-gravitating system of point masses interacting according to Newton's laws?” The frustration felt by theoreticians, who, despite the accumulation of more than 300 years of mathematical knowledge and numerical technology, have not solved the problem, even to understanding the qualitative late evolution of such systems, is compounded by the existence of observations known since Messier's time of over 100 globular star clusters. These are real and ancient systems, well approximating the idealized problem; astronomical study of their properties should have led us to an understanding of the physical situation. Galactic clusters containing smaller numbers of stars also exist in abundance. However, most of these are much younger systems and they are also subject to a variety of additional complex processes, not important in the large N, globular cluster, systems. Because of this complexity they are less well understood than globulars and will not be covered in this theoretically oriented review.
On the Dynamics of Open Clusters
Authors: Ambartsumian V. A.
Published: June 2019

It has already been pointed out in the literature that due to several causes, open star clusters dissipate with time. For instance, Rosseland showed that when external stars move through a cluster, they cause a perturbation of the motion of the stars in the cluster and could transfer enough momentum to individual stars to cause their escape from the cluster's gravitational field. In this way the cluster will lose stars gradually, i.e., it will dissipate. According to Rosseland the time needed for the star cluster to dissipate following the outlined mechanism is 1010 years. However, as pointed out by the author of this article in the supplement to the Russian edition of Rosseland's book, there is another factor that makes the life of the open cluster even shorter: the stars in the cluster have close encounters with each other, as a result of which they exchange kinetic energy and gradually tend towards the most probable distribution, i.e., a Maxwell-Boltzmann distribution. And this, as we shall see shortly, also causes the dissipation of the cluster.
The possibility of estimating tidal perturbations of Jupiter's Galilean satellites
Authors: Lieske Jay H.
Published: June 2019

Recent measurements in the infra-red of the energy emitted by Io suggest that if the observed emission is due to tidal dissipation in Io, then one should observe a very large secular acceleration of Io in its orbit. The purpose of this paper is to investigate the observational evidence which might be examined to verify that hypothesis. We have assembled the largest collection of eclipse observations extant and investigate the possibility of observing secular drifts in the period of Io. Analysis of eclipse observations requires the knowledge of good tables of ΔT and we explore the implications of the standard lunar acceleration of Spencer-Jones ṅMoon = −22.44 arcsec/cy2 versus that of Morrison and Ward ṅMoon = −26.0 arcsec/cy2. Preliminary results suggest that large tidal accelerations of Jupiter's satellites do not exist at the suggested magnitude and hence the heat flux measurements probably represent an episodic occurrence.
On calculation of relativistic effects in numerical prediction of the artificial satellite motion
Authors: Bordovitsyna T. V. , Sharkovsky N. A.
Published: June 2019

This paper discussed the algorithm of the calculation of relativistic effects in numerical prediction of the artificial satellites motion. An attempt to estimate the values of relativistic effects in the motion of two artificial satellites Navstar and Lageos is made. These values are compared with the quantities of other weak perturbations and the errors of the calculated position of the satellite due to the inaccurate approximation of perturbations.
The international atomic time, definition, realization
Authors: Guinot B.
Published: June 2019

The International Atomic Time TAI is a realized time scale which is ultimately used for comparisons between the observations and dynamical theories. Its definition should tell us unambiguously what an ideal TAI should be. It is also important know the uncertainties of the implementation of this definition.

Concerning the definition, there is an apparent divergence between the physicists for whom TAI is a coordinate-time and the astronomers who often consider it as a proper time. This matter should be clarified and it might be advisable that IAU adopts a recommendation on this topic, based on the already existing CCDS and CCIR definitions, but completed for the specific uses in astronomy. The present TAI definition refers to the geoid. Some years will elapse before the tidal effects be observable. Nevertheless, it is desirable to have some exchanges of views on an improved definition.

The accuracy (conformity with the definition), stability and precision of reading of TAI are progressively improving. Present and past properties will be briefly reported.
Radial Velocities of Remote Globular Clusters
Authors: Peterson Ruth C.
Published: June 2019

Radial velocities good to 25 km/s have been measured for the remote globular clusters Eridanus, NGC 2419, Palomar 3, Palomar 4, Palomar 5, Palomar 14, and Palomar 15. Spectra with a resolution of 3.0 A were recorded for 4 to 10 stars at a time in each cluster, using an aperture plate with the KPNO 4m telescope, R-C spectrograph, Simmons camera, and baked IIIaJ plates. Radial velocities for each star were determined from the position of the night-sky emission feature near 4360A with respect to several strong atomic features in the vicinity.

For two remote systems, Eridanus and Palomar 14, the radial velocity transformed to the galactic rest frame is large enough to suggest a total mass for the Galaxy of 1012 M⊙, and a comparable mass is indicated from the average rest-frame velocities of the remote systems. A full presentation of the measurements and results will appear in the October 1, 1985, issue of the Astrophysical Journal.
The Search for Dark Matter in Draco and Ursa Minor: A Three Year Progress Report
Authors: Aaronson M. , Olszewski E.
Published: June 2019

We report the cumulative results of an on-going effort to measure the stellar velocity dispersion in two nearby dwarf spheroidal galaxies. Radial velocities having an accuracy ≲ 2 km s−1 have now been secured for ten stars in Ursa Minor and eleven stars in Draco (including 16 K giants and 5 C types). Most objects have been observed at two or more epochs. Stars having non-variable velocities yield in both dwarfs a large (∼ 10 km s−1) dispersion. These results cannot be explained by atmospheric motions, and circumstantial evidence suggests that the effects of undetected binaries are also not likely to be important. Instead, it seems that both spheroidals contain a substantial dark matter component, which therefore must be “cold” in form.
Hot Coronae Around Early-Type Galaxies: Evidence for Dark Halos
Authors: Forman W. , Jones C. , Tucker W.
Published: June 2019

The analysis of the X-ray emission from a sample of 55 bright early-type galaxies shows that hot gaseous coronae are a common and perhaps ubiquitous feature of such systems. The X-ray emission can be explained most naturally as thermal bremsstrahlung from hot gas (kT ≈ 0.5–1.5 keV) which may be accumulated from mass loss during normal stellar evolution. The presence of these coronae shows that matter (109−1010 M⊙) previously thought to be expelled in a galactic wind is instead stored in a hot galactic corona which may be heated and powered by supernova explosions. Perhaps the single most important feature of these coronae is that they provide a unique tracer of the gravitational potential in the outer regions of bright early-type galaxies. In this paper we describe the X-ray properties of these coronae (gas mass, temperature, and extent) and discuss their implications for the presence of massive dark halos around individual early-type galaxies. We find total masses of early-type galaxies up to 5 × 1012 M⊙. We estimate mass-to-light ratios for early-type galaxies and find values up to ∼100 (in solar units), similar to those found for the larger dynamical systems of groups and clusters.
Gravitational Lenses and Dark Matter: Theory
Authors: Gott J. Richard
Published: June 2019

In principal, gravitational lenses can be used to study dark matter in a variety of ways. They can provide information on masses of lensing galaxies, circular velocities in halos, the value of Ω in condensed objects, and the constitution of heavy halos (whether they are made of low mass stars or not). They can tell us whether mass and light are distributed equally, provide insights on mass in groups of galaxies and on exotic dark matter such as strings and non zero Λ. As an example, the existance of the normal lens case QSO 2016 with zQ = 3.27 allows one to set the limit qo > −2.3.
Clustering Properties of Cold Dark Matter Universes and the CFA Redshift Survey: A Uniform Comparison
Authors: Nolthenius Richard , White Simon
Published: June 2019

We have compared the properties of galaxy groups in the CfA redshift survey to those in the cold dark matter simulations of Davis, Efstathiou, Frenk and White (1985). Redshift catalogs (four realizations) were made from the open universe (unbiased; mass follows light) simulations at expansion factors of 1.8 (Ω=.3, labelled T1) and 3.2 (Ω=.2, labeled T2) relative to initial conditions, and from the biased formation version of the Ω=1 simulation (5 realizations) at expansion factor 1.4. The T1, T2 and biased catalog sets were volume limited at distances of 5000, 3000 and 6500 km s−1 respectively, and magnitude limited (m≤14.5) beyond. They were then randomly culled by 25%, 9% and 10%, respectively, to match the density of comparison versions of the CfA Redshift Survey which were similarly volume limited. We have devised a percolation type grouping algorithm which lets the linking distance on the sky increase with distance in the magnitude limited regions, while keeping the radial velocity linking criteria fixed. We've verified that this produces groups with density contrast uncorrelated with distance and (unlike the Geller-Huchra criteria) M/L uncorrelated with group size for the open models. M/L may, however, show a slight negative correlation with distance.
Profiles of Galaxy Clusters in Cosmological Scenarios
Authors: West Michael J. , Dekel Avishai , Oemler Augustus
Published: June 2019

We have studied the properties of rich clusters of galaxies in various cosmological scenarios by comparing high resolution N-body simulations with observations of Abell clusters. The clusters have been simulated in two steps. First, protoclusters are identified in large-scale simulations which represent a wide range of cosmological scenarios (hierarchical clustering, pancake scenarios, and hybrids of the two, spanning a range of power spectra). Then the region around each protocluster is simulated with high resolution, the particles representing L* galaxies. The protoclusters have no spatial symmetry built into them initially. The final clusters are still dynamically young, and of moderate densities, which should be representative of Abell clusters of richness classes 1 and 2.
Massive Halos and the Stability of Hot Stellar Discs
Authors: Athanassoula E. , Sellwood J. A.
Published: June 2019

Bulge and halo material is often invoked to explain the absence of bars in the majority of disc galaxies, although the amount required is not known, in general, and is sensitive to the shape of the rotation curve. Here we show that the necessary fraction of spherical material is also affected by the degree of random motion amongst the disc stars. Quite moderate velocity dispersion has a strong stabilising influence and our hottest disc is stable without any halo (see also Kalnajs, this volume).
Observable Consequences of Triaxial Halos
Authors: Binney James
Published: June 2019

Heavy halos are probably not axisymmetric. During disk formation, the visible parts of disk galaxies are likely to have aligned their principal axes with those of the surrounding halos, but it is less clear that early-type galaxies are aligned with their halos. Triaxial halos may possibly sustain, or even excite, the warps often seen in the outer parts of disks. Polar rings and ripples around elliptical galaxies provide promising probes of the triaxiality of halo potentials.
Galaxy Formation in a Universe Dominated by Cold Dark Matter
Authors: Bertschinger Edmund
Published: June 2019

ABSTRACT
The mass spectrum of bound baryonic systems (galaxies and globular clusters) is computed as a function of redshift in an Einstein-de Sitter (Ω=1) universe dominated by weakly interacting, cold dark matter. Baryons are assumed to fall into primordial density peaks in the cold particle distribution when the mass in the peaks exceeds the baryon Jeans mass. The distribution of peaks is computed using Gaussian statistics. As the universe expands the baryonic mass attached to a given peak increases because of infall (treated in a spherical approximation), and new peaks of lower amplitude become nonlinear. Globular clusters form first (by z∼40 if the galaxies represent a biased mass distribution). The remaining gas may be reheated to ∼10000 K if a few percent of globular cluster (or Pop. III) stars are very massive. Reheating increases the baryon Jeans mass and delays galaxy formation until z≲10. The present method reproduces the shape (but not the amplitude) of the Schechter galaxy mass function when merging of substructure is included in an approximate fashion.
Limits on the Missing Mass in Dark Stellar Remnants
Authors: Jones Janet E. , Mellor Philip , Storm Jesper
Published: June 2019

A set of comprehensive computer models for the chemical evolution of galaxies have been used to determine the limits on the amount of mass that could exist in the form of dark stellar remnants deriving from normal stellar evolutionary processes. In these models, the instantaneous recycling approximation is not assumed: stars are binned into 10 mass intervals, with different lifetimes, yields and remnant masses. The models were run using many different values for the IMF (including non-Salpeter and varying IMFs), star formation rates, yields, remnant masses, gas infall and outflow rates, primordial metalliciy and initial conditions. The Galaxy is described by a two-zone halo-disk system, where gas from the halo falls onto the disk. Elliptical galaxies are described by single-zone models.
The Missing Mass and the Solar Neutrino Problem
Authors: Spergel David
Published: June 2019

If the halo of our galaxy is composed of weakly interacting particles, they will be captured by the sun. If the mass of these particles exceed 5 proton masses, they will remain in the Sun where they will serve as an effective means of transporting energy in the solar core. They will make the Sun's core more nearly isothermal, thus decreasing the rate of the PPIII reaction. If the halo is composed of particles with masses between 5 and 10 GeV and cross section between 10−34 and 10−37 cm2, this mechanism could resolve the solar neutrino problem. If these particles exist, they could be detected by a low temperature detector. However, if the particles annihilate in the Sun, (e.g. Photinos or Scalar Neutrinos), their number density will be too low.
Evidence for Activity in the Spiral Galaxy NGC4319
Authors: Sulentic Jack W.
Published: June 2019

Radio and optical evidence for activity in the spiral galaxy NGC4319 is presented. N4319 appears to be one of the first spirals to exhibit double lobe radio structure outside of the nuclear regions. The optical data show that 1) the quasar M205 is connected to the nucleus of N4319 and 2) that a similarly connected region on the opposite side of the nucleus is expanding towards us with V ~ 103 km s−1. It is suggested that the unusual Hα/[NII] λ 6583 ratio (≤ 0.3) indicates that the entire central (7 kpc diameter) disk of N4319 has been shock excited by this activity.
Optical Evidence for a Dust Ring in the Centre of M 82 and (OR?) a Flat Star Burst Region
Authors: Notni P. , Bronkalla W.
Published: June 2019

A dust ring surrounds the central starburst region in M 82, resulting in strong additional reddening of light emerging near the equator. The starburst is contained in a flattened, optically thick region inside this ring. The concentration of scattered light near the minor axis is explained as the combined action of the cos ϑ-emission-law of the flat source and the shadowing by the ring. The dust ring may be spatially coincident with the CO-ring.
A solar model with turbulent diffusion mixing: surface abundances and oscillations
Authors: Lebreton Y. , Berthomieu G. , Provost J.
Published: June 2019

A solar model which includes the plausible presence of a mild mixing in the solar inner radiative zone is presented. The mixing is supposed to result from the hydrodynamical instabilities which may occur in a differentially rotating medium leading then to turbulent diffusion. The model includes up-to-date input physics and takes into account the inhibition of the turbulent motions, due to molecular weight gradients (i.e. for Mr/M⊙ < 0.5). The properties of the model are compared to the standard model properties and to observational results: this turbulent diffusion mixing (TDM) improves the results on surface abundances of the light elements (7Li, 3He) and does not reduce the solar neutrino flux relative to the standard model. Moreover preliminary results show that this TDM weakly modifies the oscillation frequencies.
On the technique of the inversion of helioseismological data
Authors: Brodsky M.A. , Vorontsov S. V.
Published: June 2019

The asymptotic inversion technique is developed, including independent determination of the sound speed profile and frequency dependence of the effective phase shift. Numerical results are presented.
Solar cycle dependence of solar p nodes
Authors: Isaak G.R. , Jefferies S.M. , Mcleod C.P. , New R. , van der Raay H.B. , Palle P.L. , Regulo C. , Cortes T. Roca
Published: June 2019

Data obtained at Izana (Tenerife) and Haleakala (Maui), using optical resonant scattering with a potassium vapour cell over the years 1980–84, are used to determine the frequencies of the low ℓ p modes. Possible variation in these frequencies with the solar cycle are investigated.
Solar diameter and solar rotation during the Maunder minimum
Authors: Ribes E. , Ribes J.C. , Barthalot R.
Published: June 2019

The Paris observatory is in possession of a 53 y record of solar diameters and sunspot positions during the Maunder minimum (1666–1719). For the period (1666 to 1684), the solar diameter was 32′9″ and slowly decreased down to 32′6″ when sunspot activity had resumed. Nowadays, the solar diameter is 32′2″ when taking into account of the solar irradiance. During the same period, the sunspot rotation was smaller than the present one (3% less near the equator), and the differential rotation was greater.

The two phenomena (a larger Sun and a slower rotation) suggest that the Sun undergoes a cyclic expansion and contraction, on timescale of several centuries.
A photometric search for ‘5-min’ oscillations in the components of Alpha Centauri and two other double stars
Authors: Balona L. A. , Marang F.
Published: June 2019

The discovery of global solar 5-min oscillations has prompted the search for such oscillations in other stars. The main problem in detecting these variations is their expected small amplitude (in the sun it is less than 1 m/s in velocity and 10−6 in integrated light). Two recent studies by Fossat et al. (1984) and Noyes et al. (1984) have suggested that the 5-min oscillations in α Cen and ε Eri may have been detected.

We attempted to detect these oscillations by means of conventional broad-band photometry in the components of three double star systems (α Cen, HR4677 and HR5568). We selected these stars because they cover a wide range of spectral types (F2V to M2V). It was hoped that there may be a region where the pulsation amplitudes are particularly large. By using one component of a double star system to correct for transparency variations in the other, we also expected to obtain a larger signal-to-noise ratio.
Infrared Helioseismology: Detection of the chromospheric mode
Authors: Deming Drake , Glenar David A. , Käufl Hans Ulrich , Espenak Fred
Published: June 2019

We have observed solar oscillations using a new instrumental technique in a relatively unexplored region of the solar spectrum. We obtained a 2-day sequence of line profiles, at 30 second intervals, for a pure rotation line of OH at 11.065 μm, using a laser heterodyne spectrometer to view a 2 arc-sec portion of the quiet Sun at disk center. The continuous opacity of the solar atmosphere increases with wavelength longward of 1.6 μm, so 11 μm lines are formed in the upper photosphere, near h = 250 km. In this region the OH rotational transitions have δJ=1 collisional rates which are two orders of magnitude larger than their radiative rates. Hence the OH lines have source functions which are equal to the Planck function, and the high spectral purity provided by the laser heterodyne technique makes their line profiles especially appropriate for investigating the dynamics of the solar atmosphere. We have recently reported (Deming et al. 1986) that oscillations in this OH line show evidence of a resonance due to a cavity in the solar chromosphere.
Convective overshoot and upper boundary conditions
Authors: Nesis A.
Published: June 2019

Calculations of the frequency of solar oscillation are sensitive to the upper boundary conditions of the model. Our investigations of the velocity fields of the overshoot layers (photosphere) have shown that there is a minimum of velocity at about 200 km above τ = 1: We suggest that this minimum provides a natural upper boundary condition for the calculations of solar oscillation. The propagation of sound in these layers has to be regarded as a propagation in a turbulent medium.
The Photographic Observations of Some Planetary Nebulae
Authors: Hao Xiangliang
Published: June 2019

The first planetary nebula was discovered by Messier in 1794. But for some reasons it has not been studied detail for a long time, especially for the central star Of planetary nebula. The primary research for these objects showed that the lifetime of a planetary nebula is about 5 104 years, but in this period the luminosity of central star varies from 63 L⊙ to nearly 3.5 104L⊙ and then decrease to 100 L⊙; its temperature changes from 3.4 104 to 105K and then begins to decrease (Seaton 1966). The radius of central stars also have fast varies in planetary nebula phase. For these reasons we consider that in the planetary nebula phase the activities of central star is very drastic and the result of these activities must cause some variation at the surface of central star witch may be detected on the earth, especially for the surface light variations. Some observers have been trying to find the luminosity variations in central stars. But until now no one has made systematical survey for these. Since the different authors used different instruments amd different processing methods at different places which may be caused a lot of uncertainty in the photometry of planetary nebulae and central stars. So it is hard to decide whether the differences between the authors or the essential variations of the objects is responsible of the observing differences. Therefore, we have selected over fifty planetary nebulae to observe for a long period at Beijing Observatory using the same instrument and the same processing method. From these observations we may determine the light variations and the brightness of the planetary nebulae and central stars more correctly.
The Neutral Envelopes of Planetary Nebulae: Molecules and H I
Authors: Huggins P.J.
Published: June 2019

This paper summarizes recent developments in the study of planetary nebulae using observations of molecular lines and the 21 cm line of H I. The observations reveal that many planetary nebulae are surrounded by envelopes of neutral gas, whose mass often exceeds that of the ionized nebulae. They also provide valuable information on the physical and chemical properties of the envelopes, their structure, and kinematics. The neutral envelopes firmly link the formation of planetary nebulae with the mass loss by AGB stars, and can play an important role in the subsequent evolution of the nebulae.
Monochromatic CCD Images of Three Planetary Nebulae
Authors: Feibelman Walter A.
Published: June 2019

We present monochromatic false-color images of three planetary nebulae obtained by means of a CCD camera at the f/13.5 focus of the 0.91m reflector of the Cerro Telolo Interamerican Observatory in August, 1985. The resultant image scale is 0.363 arcsec square per pixel. The objects, IC 1297, NGC 7009, and M2-9 were imaged through narrow band filters in the V band, [O III] λ5007, and Hα λ6563, respectively. The V band filter corresponds to the standeard Johnson V magnitude. The λ5007 filter has a FWHM of 14 Å. The Hα filter has a FWHM of 73 Å, thus including contributions from the [N II] λλ6548, 6584 lines. IC 1297 shows a double shell structure with a pronounced bright rim at the extreme edge of the faint outer envelope, suggesting that it is density bounded. NGC 7009 (the “Saturn” nebula), in addition to the well-known double shell and extended W-W ansae, also shows a faint large, circular outer halo which strongly suggests that NGC 7009 is a member of the rare class of triple-shell nebulae. The bipolar object M2-9 (the “Butterfly” nebula) shows a bright, non-stellar central core from which the wings extend in a nearly N-S direction. Condensations in the wings are seen particularly well for the [O III] λ5007 images. The CCD images were obtained by B. Schaefer at CTIO and were processed at the Goddard Image Processing Facility.
Hα Morphological Classification of Planetary Nebulae
Authors: Schwarz Hugo E. , Corradi Romano L.M. , Stanghellini Letizia
Published: June 2019

Using the data from the catalogue of PNe images of Schwarz et al. (1992), we have classified 255 nebulae into 5 morphological groups. The images were taken through a filter centred on the Hα line and included the [NII]6583 line. Most of the observations were made with the 3.5m ESO NTT during commissioning time. The main groups are called: stellar (st), irregular (i), elliptical (e), bipolar (b), and point-symmetric (p). The ellipticals are subdivided into: simple (e), multiple event (em), and inner structure (es) types. The bipolars into: simple (b), and multiple event (bm). The point-symmetric objects into: simple (p), and multiple events (pm).
A Systematic Study of IRAS Selected Proto-Planetary Nebula Candidates
Authors: Hu J.Y. , Jiang B.W. , De Jong T. , Slijkhuis S.
Published: June 2019

A complete sample of PPN candidates was selected mainly based on the IRAS colors(Hu et al.,1990). For total 62 unknown objects in the sample we have made 1. ground-based infrared astrometry; 2. optical identifications; 3. near infrared and optical photometry; 4. optical spectroscopic observations; 5. radio molecular line observations(OH maser and CO thermal lines); and 6. check the optical variations from historical plates. Some additional observations such as high resolution spectraoscopic, optical/NIR CCD imaging observations for particularly interested objects were also carried out.
FI Lyr: A Candidate Binary System Consisting of Carbon-Rich and Oxygen-Rich Companions
Authors: Wang J.J. , Hu J.Y. , Zhou X.
Published: June 2019

FI Lyr=IRAS18401+2854 is listed in the GCVS as type of SRb, the spectral type is M. In the IRAS LRS Catalog it is classified as 41, namely having the SiC feature at 11.3μm from a carbon-rich dust shell. We have obtained optical and near infrared spectra in the same period, but they show different chemical natures. We suggest that FI Lyr is a good candidate of a binary system consisting of carbon-rich and oxygen-rich companions.
Near–Infrared Imaging of Proto-Planetary Nebulae
Authors: Clegg R.E.S. , Walton N. A. , Barlow M.J.
Published: June 2019

It is not really known how low and intermediate mass stars eject mass to form PNs. We present preliminary results from a programme of near–IR imaging, in which we study a sequence of objects, from extreme AGB stars through proto–planetaries to young, compact PNs. We aim to study the sequence of morphologies, to see where the onset of bipolar shaping occurs, and to use the IR molecular hydrogen lines to map neutral regions around ionized nebulae.
Modelling PN Formation from Hydrodynamics and Radiation
Authors: Mellema G.
Published: June 2019

The formation of planetary nebulae from the mass loss remnants of previous phases forms an interesting problem in both hydrodynamics and astrophysics. Not in the least because of the asphericity that most PNe show. The origin of this asphericity is still largely a mystery. Binarity is the most favoured explanation at the moment (Morris 1987)
HST FOS Observations of KPD0005+5106: A Subluminous WN-WC Descendant by Ongoing Mass Outflow?
Authors: Sion Edward M. , Downes Ronald A.
Published: June 2019

We report the results of spectroscopic observations of the ultra-high excitation, helium-rich, pre-white dwarf KPD0005+5106 obtained with the Hubble Space Telescope Faint Object Spectrograph (FOS) in 1991 May and July with the red (FOS/RD) and blue (FOS/BL) Digicon detectors. The data reveal a rich line spectrum both in absorption and in emission with ultra-high excitation species present including O VIII, N V, possibly C V, Fe VI, Fe VII and numerous weaker high n, low l, transitions of C IV and O VI as well as the predominant He II (3 → n) and He II (Balmer α) absorption lines. There is a strong emission complex at 2981A which we identify primarily as three transitions of N V commonly seen in WN Wolf-Rayet spectra. We present evidence that high ionization species in emission (O VIII, N V, C IV, Si IV) and in absorption (He II, Fe VI, Fe VII) are longward-shifted relative to the far UV resonance (circumstellar) absorption lines by 25–50 km/s. Based upon the detected species, line velocities, line widths and emission features, we conclude that (1) KPD0005 is the very likely the evolutionary descendant of a WN-WC subluminous Wolf-Rayet progenitor and (2) has ongoing, possibly episodic, mass outflow.