bluuebunny/crossref_metadata_2025 huggingface dataset:
Tracing Large-Scale Structure with Galaxy Objective-Prism Spectra
Authors: Parker Q.A. , Macgillivray H.T. , Beard S.M.
Published: June 2019

A new and promising use of galaxy objective-prism spectra as a means of highlighting features in the large scale galaxy distribution has been recently reported by Parker et al. (1987). The technique relies on the property that galaxies with identifiable 4000Å features in low dispersion objective-prism spectra are mostly ellipticals (Cooke, 1980), and that early type galaxies seem to delineate structure and clumpiness in the galaxy distribution (e.g. Giovanelli and Haynes, 1982). The effect is most striking when large numbers of objective-prism galaxy spectra are considered. Figure 1 gives the X-Y plot for 1539 galaxies with 4000Å features to Bj=18.7 in one UKST field out of a manually measured sample of 2903 galaxy prism spectra. Substantial clumpiness is evident. This technique can trace structure in the galaxy distribution across many UKST fields to depths of 400 h−1Mpc.
Results from the 1000 Galaxy Sample: The Correlation Function at Z = 0.75 and the Evolution of the Characteristic Luminosity
Authors: Loh Edwin D.
Published: June 2019

This paper announces two results from a catalog of redshifts and fluxes for a flux limited sample of 1000 field galaxies (Loh and Spillar, 1986, Ap. J., 307, L1).
Space Distribution of the Richest Abell Clusters of Galaxies
Authors: Kalinkov M , Kuneva I
Published: June 2019

We discuss four samples from the Abell (1958) catalog of clusters of galaxies. Our samples are drawn out from the Abell sample and all clusters have richness 2 and 3. With Ho = 100 km/s/Mpc and qo = +1, we examine the following volumes, defined for both galactic hemispheres:

(i)

RG 3: b 40° for 0° < 1 360° and b 30° for 90° < 1 240°, distance 300 < R < 750 Mpc, N = 35 clusters, 30 of which with known redshift;

(ii)

RG 3: b −35° for 15° < 1 232°, 150 < R < 600 Mpc, N = 15 (13);

(iii)

RG 2: b and 1 as (i), 60 < R < 525 Mpc, N = 110 (55);

(iv)

RG 2: b and 1 as (ii), 120 < R < 600 Mpc, N = 102(14).
X-ray selected clusters of galaxies
Authors: Gioia Isabella M. , Maccacaro T. , Morris S. L. , Schild R. E. , Stocke J. T. , Wolter A.
Published: June 2019

Studies of the evolution of X-ray emission from clusters of galaxies have so far used optically discovered distant clusters then observed at X-ray wavelengths. A different approach to the study of cluster evolution is to use clusters selected directly by their X-ray emission since X-ray selection is extremely successful at discovering high redshift clusters (up to z = 0.5). The Extension of the Medium Sensitivity Survey (Gioia, Maccacaro and Wolter, 1987), a flux limited sample of serendipitous X-ray sources discovered with the Einstein IPC, has been used to select 68 optically identified clusters and 66 possible candidates (using X-ray isointensity maps and optical POSS and ESO prints). Their X-ray fluxes are in the range 10−13 – 10−12 ergs cm−2 s−1 in the 0.3–3.5 keV energy band. Few misidentifications are expected, thus the results presented here have to be considered as preliminary. This sample can be used to study the X-ray logN-logS, the cluster luminosity function and its possible evolution with cosmic time, and also to compare the properties of X-ray selected clusters with those of samples selected by other techniques. Since the identification process is still in progress, and has not proceeded completely at random, the subset of identified sources is not representative of the entire population. With this caveat in mind we have constructed the redshift and X-ray luminosity distributions for the clusters for which we have spectroscopic observations. 68% of the clusters are at z > 0.1, 34% at z > 0.2, and 12% at z > 0.3. Their X-ray luminosities range from about 3 × 1042 to 1045 ergs s−1. At present the lack of a redshift determination for many of the cluster candidates in our sample prevents us from studying the cluster luminosity function. W e can however derive their logN(>S)-logS relation.
The Cross-Correlation of Abell Clusters with the Lick Galaxy Counts
Authors: Lilje Per B. , Efstathiou G.
Published: June 2019

We have analysed the cross-correlations between Abell clusters and the 10′ × 10′ Lick galaxy counts. The main new features of our analysis are as follows: (a) we correct for gradients in the Lick counts that depend only on galactic latitude; (b) we check the effects of applying a filter to remove (likely artificial) gradients on scales >20°; (c) redshifts for Abell clusters are used to compute a cross-correlation function wcg(σ), where σ = vϑ/Ho is the projected separation between a cluster with recession speed v and a galaxy at angular distance ν from the cluster centre; (d) the amplitude of the spatial cross-correlation function ξcg(r) is estimated using modern determinations of the galaxy luminosity function. Our results show that the shape of ξcg is reasonably well determined on scales r ≲20h−1 Mpc. On larger scales, the results depend sensitively on the corrections for large-scale gradients in the Lick counts. The results based on wcg(σ) are well described by a power-law model ξcg(r)≃(r/8.8h−1 Mpc)−2.2, while the angular cross-correlations for Abell clusters in distance class D=5 are better described by the model ξcg(r)=(r/6h−1 Mpc)−2.3 + (r/7h−1 Mpc)−1.7. Seldner and Peebles (1977) derived a larger amplitude for ξcg because they assumed a different luminosity function. We compare these results with theoretical predictions of ξcg in the Ω=1 biased cold dark matter (CDM) model. On scales 1 h−1 Mpc ≲ r ≲ 10 h−1 Mpc, the theoretical predictions for ξcg are in surprisingly good agreement with our observational estimates. On smaller scales, the CDM model gives too high an amplitude whereas on larger scales the predicted amplitude is too low. Neither of these discrepancies is particularly serious.
On the Goodness of Different Mass Estimators from N-body Simulations
Authors: Perea J , del Olmo A. , Moles M.
Published: June 2019

N-body models were run in order to test the mass estimators considered by Heisler, Tremaine and Bahcall (1985, HTB), when systems with a large number of mass-points with a non-flat mass-spectrum are considered. The initial conditions of the models were a analytic King profile for the number density, a Gaussian velocity distribution function and a Schechter-type mass spectrum. The models were left to evolve from a far from virial initial configuration, so a violent collapse occurs before the system reachs equilibrium. The code we use was NBODY2 code kindly provided to us by Dr. S. Aarseth.
From 2-D to 3-D by Maximum Entropy Method
Authors: Lahav Ofer , Lynden-Bell Donald , Gull Steve F.
Published: June 2019

We present a method of estimating distances to clusters of galaxies from twodimensional catalogues. The angular diameters (or magnitudes) of galaxies are used as distance indicators. The mapping from 2-D to 3-D is done by using a ‘diameter function’ (analogous to a luminosity function), which is based on a redshift survey from a section of the sky. The problem is formulated as follows. The number of galaxies with a metric diameter D in a volume element d3r is:

where n(r) is the ‘true’ number density of galaxies at position r, n& is the mean number density of galaxies in the universe and ϕ(D)dD is the diameter function. We assume that within a narrow cone n(r) = n(r) and then express N(> θ), the number of galaxies greater than a certain angular diameter θ. In a discrete form we write the relation as:

where ni is the density at the i – th distance bin and Pik is our ‘point spread function’, which is a function of the diameter function and Galactic obscuration. We express (2) in terms of χ2 statistics over the measurements, and require it to be less than a certain value. The entropy of the image is expressed as:
Observed Distortions (From Linearity) of the Hubble Flow and Bias in the Data
Authors: Giraud Edmond
Published: June 2019

Several tests can be made to get a rough idea of the Malmquist effect in a given set of galaxies. They are : (1) The progressive loss of late types pirals (Scd or later), of low luminosity classes, of objects with small rotation velocity, or small internal dispersion, as we go to larger distances. (2) The variation of the slope of the Tully-Fisher relation, of the Faber-Jackson relation or of the Λ index with distance (differential bias).
Nonlinear Evolution of Acoustic Waves in Dust Interacting with Dark Matter in Newtonian Cosmology: Biasing, Voids, and the Kadomtsev-Petviashvili Equation
Authors: Kates Ronald E.
Published: June 2019

This paper shows that the Kadomtsev -Petvlashvili equation of type I

governs the evolution of certain weakly nonlinear fluctuations on a staticor very slowly varying cosmological background. The model consists of a mixture of nonrelativistic, collisionless (here after called “dark”) matter at nonzero temperature together with a smaller amount of zero-temperature rotation- free dust. The two components are coupled only by gravitational forces.
T.N. Thiele And The Carte Du Ciel
Authors: Kristensen Leif Kahl
Published: June 2019

T.N. Thiele participated in the astrographic conference in Paris 1887 and was the first theoretician to reduce and analyse the photographic plates of the Henry brothers. He was an enthusiastic supporter of photographic astrometry because of its elimination of personal errors. However, for different reasons he did not want the Copenhagen Observatory to take responsibility for a Carte du Ciel zone. Thiele's life and work and his plans for the development of astrometry are presented.
Construction Of The System Of Positions And Proper Motions In The FK5
Authors: Schwan H.
Published: June 2019

The various steps for the derivation of a fundamental catalogue are described and a report on the present status of the work on the FK5 is given. The observational material for the determination of the FK5 system is described and the systematic corrections to the FK4 are discussed.
The Development Of The Overlapping-Plate Method
Authors: Eichhorn Heinrich
Published: June 2019

The principles of focal-plane astrometry are described, as well as the development of the overlapping-plate method. In particular, the advantages and pitfalls of this method are discussed. An extensive bibliography is appended.
The Guide Star Catalog. I. Overview, History, And Prospective
Authors: Lasker Barry M. , Jenkner Helmut , Russell Jane L.
Published: June 2019

An astronomical overview of the Guide Star Catalog, together with its history, the properties of its current implementation, and the prospects for enhancement are presented.
The Yale Parallax Catalogue
Authors: van Altena William F. , Lee John T.
Published: June 2019

A new edition of the General Catalogue of Trigonometric Stellar Parallaxes is being prepared at the Yale University Observatory. The Catalogue will include all published photographic parallaxes, a reference to the source of the published parallax, UBV photoelectric photometry, MK spectral types, cross identifications with other catalogues, data on the binary nature of the stars and auxiliary information to aid in determining the reliability of the data. An analysis of the parallaxes corrected to absolute has been made to study the accidental and systematic errors of the parallaxes. The new edition will be available in both printed and magnetic tape versions.
Proper Motion Determination Of The X-Ray Object 3A2254-033 Using The Astrographic Catalogue Of The San Fernando Zone
Authors: Argue A.N. , Quijano L.
Published: June 2019

The Astrographic Catalogue has been used to measure the proper motion of the X-ray object 3A2254-033.
The Mama Machine: Proper Motions From Digitization Of Centenary Plates
Authors: Guibert Jean
Published: June 2019

MAMA was designed to digitize a Schmidt photograph in 2 hours, and a Carte du Ciel plate in 30 minutes, with a positional accuracy of 1 micron. Comparison of recent photographs with Carte du Ciel plates can thus be performed on a large scale to determine proper motions of stars down to visual magnitude 14 over a time interval of about ninety years. The poster presents the main features of the system and illustrates some programmes undertaken in various domains.
Towards The Definition Of A Unified Celestial Optical/Radio Reference Frame
Authors: Hughes J. , Johnston K. J. , de Vegt Ch.
Published: June 2019

An almost inertial celestial reference frame based upon extragalactic sources is in the process of being established. This reference frame is to be global with a minimum density of one source per 100 square degrees. The source positions will be based upon radio observations and will allow optical reference frames to be related to this frame at the 0.03 arc second level.
A Program For A New Reduction Of Plates Of The Astrographic Catalogue
Authors: Röser S. , Jahreiß H.
Published: June 2019

The Astrographic Catalogue is the major source of accurate first epoch coordinates of stars down to about 11 mag all over the sky. Therefore it could be the ideal tool for the determination of proper motions in this range of magnitudes - see also for example Fresneau (1985). There were mainly three reasons which prevented in the past a frequent use of this catalogue:

1)

Apart from the „french“ zones (Lacroute 1981) the AC is not available in machine readable form.

2)

Only measured plate coordinates x,y and plate constants mostly derived with the AGK1 as reference catalogue have been published.

3)

The lack of easy to use software for a new reduction.
NASA's Astrometric Telescope Facility
Authors: Scargle Jeffrey D. , Nishioka Kenji , Gatewood George
Published: June 2019

NASA is planning an Astrometric Telescope Facility (ATF) for the U.S. Space Station. Space astrometric observations of unprecedented accuracy will yield many important results, including a planetary detection survey. The proposed facility is a dedicated astrometric telescope using the Multichannel Astrometric Photometer (Gatewood et al., 1987). To achieve the goal of sub-milliarcsecond accuracy requires innovative approaches to measuring technique and data analysis.
Lists of Confirmed Planetary Nebulae in the Magellanic Clouds
Authors: Sanduleak N. , MacConnell D.J. , Davis Philip A.G.
Published: June 2019

Very deep, blue and red-sensitive objective-prism plates, taken with the Curtis Schmidt telescope at the Cerro Tololo Inter-American Observatory, were used to survey both Magellanic Clouds for unresolved objects which could be classified as highly probable planetary nebulae. The high sensitivity of the baked Kodak IIIa-J emulsion at 5000 Å made it possible to detect the N1 and N2 lines of [OIII] in fainter objects than previously observed. A number of emission-line stars, compact HII regions, and very-low-excitation objects, formerly considered to be probable or possible planetaries, were recognized and excluded. The final lists contain 27 confirmed planetaries in the SMC and 100 in the LMC, a ratio equivalent to the estimated ratio of total mass in the two systems. As would be expected, most of these objects had been detected in previous objective-prism surveys but some apparently new planetaries were found.
Interpretation of the Ultraviolet Spectrum of NGC 7662
Authors: Bohlin R.C. , Harrington J.P. , Stecher T.P.
Published: June 2019

The ultraviolet emission lines that were me asured in the spectrum obtained from our rocket observation of NGC 7662 have been compared with those predicted by a set of models. The models allow a determination of the carbon abundance which is found to be solar and the C/0 ratio which is equal to unity. In order to obtain a good fit, dielectronic recombination and charge exchange between neutral hydrogen and C IV were included, both of which increase the concentration of C III. The observed continuum consists of light from the central star and from the nebula, which contributed primarily via the two photon process in the H° and the Balmer continuum.
Binary Nuclei of Planetary Nebulae
Authors: Acker Agnès
Published: June 2019

In view of the spectral similarity and the probable evolutionary relation between certain planetary nebulae (PN) and other objects that are generally binaries (symbiotic stars, Be stars, or slow novae), it is probable that many nuclei of PN are double.
Time-Dependent Effects in Planetary Nebulae Caused by Thermal Pulses in Central Stars
Authors: Tylenda R.
Published: June 2019

Nuclei of planetary nebulae are suspected to go through thermal pulses. A time scale of such pulses is of the order of 10–103 years and so it is comparable with the time of recombination in a typical planetary nebula. Theoretical models have been constructed to study evolution of ionization structure of nebulae in which the spectrum of ionizing radiation varies with time. Resulting intensities of emission lines are compared with those produced by stationary model nebulae.
The Abundances of He, N, Ne, Ar and Cl
Authors: B. Kaler James
Published: June 2019

Various abundance problems have been well reviewed by the two previous papers. The study of the compositions of planetary nebulae has been quite fruitful. Nebulae can be used to study elements which are difficult to study in stars. In particular, it has been shown that planetaries can contain matter which has undergone nuclear processing, which in turn can enhance the abundances of some elements, notably He and N. In addition, planetaries can be used to study composition gradients in the galaxy. Of particular relevance to these topics are papers by Peimbert and Torres-Peimbert (1971) (hereafter referred to as PTP) and Boeshaar (1975) on enhancement of N/O; by Kaler (1973) on He/H ratios; by Barker (1976) on He and N; by D'Odorico, Peimbert and Sabbadin (1976), Aller (1976) and Torres-Peimbert and Peimbert (1977) (hereafter referred to as TPP) on abundance gradients.
Improved Abundances in Three Halo Planetary Nebulae
Authors: Hawley Steven A. , Miller Joseph S.
Published: June 2019

With the Lick Observatory 3m telescope and image dissector scanner we have obtained new spectrophotometric observations of three halo planetary nebulae; 49 + 88°1, 108 − 76°1, and K 648. Based on the observed line intensities we are able to compute temperatures, densities, and abundances of He, 0, N, and Ne. Our data show that the helium abundance in the halo planetaries is normal with respect to disk planetaries. Oxygen is consistently less abundant in the halo planetaries by factors of 4, 12, and 20. The ratio N/0 in 49 + 88°1 and K 648 is typical of disk planetaries while N/0 in 108 − 76°1 is an order of magnitude larger. This suggests to us the possibility that varying amounts of mixing of CNO processed material has taken place in the progenitor stars. We do not detect [S II] or [S III] emission in K 648 or 108 − 76°1. In 49 + 88°1 [S II] and [S III] are present but weak and we derive an S abundance which is roughly a factor of 10 smaller than for disk planetaries. K 648 has the lowest abundances of 0, N, and Ne of all these halo planetary nebulae.
Some Properties of Dust in Planetary Nebulae
Authors: Panagia Nino
Published: June 2019

From an analysis of infrared, optical, ultraviolet and radio data of a number of planetary nebulae, it is found that the dust mixed with the ionized gas mainly consists of relatively large, graphite-like grains.
Millimeter-Wave Observations of Planetary Nebulae
Authors: Johnson Hugh M.
Published: June 2019

Observations of the integrated continuum flux density of several stellar planetary nebulae have been made at 90 GHz. These are reported, with some remarks on their significance for objects with positive radio-frequency spectral index, and to display graphically their relation to published microwave and near-infrared data. The 90-GHz data have been obtained with the 11-m dish of the National Radio Astronomy Observatory* on Kitt Peak, under the Lockheed Independent Research Program. Three of the objects have been included among a dozen stellar planetary nebulae observed with the Fabry-Perrot interferometer at the Cerro Tololo Inter-American Observatoryt so as to provide kinematical information with the microwave spectral data, since they are related in the theories of the positive spectral index that appeared in 1975. The Fabry-Perot observations are reported in Astrophys. J. 1977 September 15. No other journal article is yet in press.
A Study of the Planetary Nebulae Abell 30 and Abell 78
Authors: Cohen M. , Hudson H.S. , O'Dell S.L. , Stein W.A.
Published: June 2019

We have studied the central regions of the planetary nebulae A 30 and A 78 by UBVRI photometry, optical spectroscopy, and near-infrared photometry. The spectra contain high-excitation emission lines and strongly resemble those of Wolt-Rayet stars of the carbon sequence. We infer stellar temperatures > 50,000°K. The observed 3.5-ym flux of each nebula exceeds reasonable extrapolations of both the stellar flux and any possible free-free emission. The colour temperature of this excess between 2.28 and 3.5 /im is ∼ 1000°K. For each nebula, the aperture dependence of the excess emission suggests an extended (y10 arc-sec radius) region centred on the nucleus. Thermal radiation from a distribution of dust that is concentrated near the nuclei seems the most plausible explanation for the excess, but no theory of dust formation or heating seems totally adequate at present. (Paper will appear in the Monthly Notices of the Royal Astronomical Society.)
The Physical Properties of Large Scale Systems from Optical Observations
Authors: Abell G. O.
Published: June 2019

Holmberg's (1937) analysis of the distribution of double and multiple galaxies provided what may have been the first hint of a local inhomogeneity of greater scale than that of the Local Group. the idea of a Local Supercluster was subsequently revived by de Vaucouleurs (1953, 1956, 1958). the analyses of others, as well as the continuing study of de Vaucouleurs himself (1976 and references cited therein) have now effectively established the reality of the Local Supercluster. Several other more remote inhomogeneities, or “clouds” of galaxies, were described by Shane and Wirtanen (1954). the writer (Abell 1958) found the distribution of rich clusters to be clumpy, and published a finding list of several apparent superclusters (Abell 1961).
The Large Scale Distribution of Radio Sources
Authors: Longair M. S.
Published: June 2019

In this brief survey, three topics will be described:
The Evolution of Galaxies: Evidence from Optical Observations
Authors: Tinsley Beatrice M.
Published: June 2019

The clearest evidence that galaxies evolve comes from the Milky Way: here we see stars with ages and lifetimes differing by 4 orders of magnitude, and with chemical compositions indicating a hundred-fold enrichment in metals between the times of formation of the halo and most disc stars. the general resolution of Olbers' Paradox also gives evidence for cosmological change: the sky is dark because galaxies turned on a finite time ago (Harrison, 1974). Here I discuss some of the further evidence for galactic evolution that is emerging from observations probing billions of years in lookback time.
QSO absorption lines and intergalactic hydrogen clouds
Authors: Peterson Bruce A.
Published: June 2019

The absorption line spectra of some QSOs are similar to the absorption line spectra imposed by the interstellar medium in our own galaxy on the spectra of hot stars (see Figure 1). the spectra of other QSOs show P Cygni profiles similar to those of hot stars with mass outflow (see Figure 2). the absorption lines in both of these types of spectra are due to the resonant transitions of hydrogen and of the more abundant elements.
Recent advances in microwave cosmology
Authors: Boynton Paul
Published: June 2019

In summary, this brief communication outlined first the recent measurement of large-scale anisotropy of the relic radiation by the Berkeley group of Smoot, Gorenstein and Muller (1977). the customary peculiar velocity interpretation of the dipole term gives v = 390 ± 60 km/sec in the direction of α = 11h.0 ± 0h.5 and δ = 6° ± 10°. These values differ from the preliminary results of Corey and Wilkinson (1976) by less than twice their reported errors.
The Theory of the Large Scale Structure of the Universe
Authors: Zeldovich Ya B.
Published: June 2019

The God-father of psychoanalysis Professor Sigmund Freud taught us that the behaviour of adults depends on their early childhood experiences. in the same spirit, the problem of cosmological analysis is to derive the observed present day situation and structure of the Universe from certain plausible assumptions about its early behaviour. Perhaps the most important single statement about the large scale structure is that there is no structure at all on the largest scale − 1000 Mpc and more. On this scale the Universe is rather uniform, structureless and isotropically expanding - just according to the simplified pictures of Einstein-Friedmann……. Humason, Hubble…. Robertson, Walker. On the other hand there is a lot of structure on the scale of 100 or 50 Mpc and less. There are clusters and superclusters of galaxies.
Primeval clusters of galaxies and the X-ray background
Authors: Kellogg Edwin M.
Published: June 2019

The X-ray telescope for HEAO-B, due for launch next year, will extend our observing power in X-ray astronomy by a very large factor. For example, its sensitivity to point sources will be 103 greater than the limit of existing X-ray sky surveys. Even more intriguing will be its capability to image the all-sky X-ray background radiation on an arc minute or sub arc minute scale. the origin of this background is still a mystery. the simplest hypothesis, that it is the integral of radiation from the more distant members of the classes of discrete X-ray sources such as clusters of galaxies, Seyferts, QSO's and other active galaxies, can only explain part of the background.
Observational limits on neutral hydrogen in primordial protoclusters
Authors: Davies R. D.
Published: June 2019

After recombination in the early Universe, gas will pass through a neutral phase on its way to condensation into galaxies and stars. Radio emission in the reshifted 21 cm line of neutral hydrogen can be used to detect condensations in the early Universe. Sunyaev and Zeldovich (1972, 1975) have suggested that primordial protoclusters may be predominantly neutral at z = 3 to 10 and may have neutral hydrogen masses ~ 1014 M⊙. Two observational approaches have been made to the search for this emission.
Non-linear effects in flat gravitating systems
Authors: Fridman A. M.
Published: June 2019

It is shown that in flat gravitating systems, such as spiral galaxies, groups of galaxies and some superclusters (which have an axis ratio of, say, 1/5) there are nonlinear effects such as the formation of collapsars in disks which are stable according to Toomre's criterion; the formation of solitons (spiral and ring-shaped), which can move with supersonic as well as subsonic velocities depending on the characteristic parameters of the disk. in an isothermal gas, shock waves can only originate in spirals with two or more arms. in the background of two bright spiral arms one may be able to trace a weaker ring structure. in contrast to supersonic spirals, the velocity of the circular structure is subsonic. A bright ring structure can in principle indicate that in such systems for some reason the adiabatic index γ is close to that of an ideal gas γ ≈ 5/3. This last point can be of interest in the future if non-isothermal perturbations will be found as seems possible in some systems. A break-up instability will lead to practically uniform enhanced star formation all over the disk; it will have a tendency to simulate narrow rings and tightly wound spirals with one arm according to the law (δσ/σO)~(t-tO)−1.
The Hypergiant Variable HR 8752 = HD 217476
Authors: Zsoldos E.
Published: June 2019

HR 8752 is one of the brightest stars of the Galaxy. Humphreys (1978) gives its absolute visual and bolometric magnitudes between −9.1 and −9.5, and between −9.2 and −9.5, respectively. The star received its variable star name, V509 Cas, in 1972 (Kukarkin et al., 1972). Radial velocity variations were first noticed by Harper (1923) and by Campbell and Moore (1928). In Harvard Ann. Vol. 44 (Pickering, 1899) there are indications for light variation at the end of the 19th century.
Steps to a New Calibration of the Spectral Type — Effective Temperature Relationship for Early-type Stars
Authors: Bohannan B. , Abbott D. C. , Voels S. A. , Hummer D. G.
Published: June 2019

The spectral type - effective temperature calibration is a cornerstone of our understanding of massive stars and their environment. Any uncertainty in determining their effective temperature is directly reflected in an uncertainty in defining the bolometric luminosity and the number of ionizing photons. We suggest that previous calibrations of bolometric luminosity and the number of ionizing photons as a function of spectral type may be uncertain by at least a factor of 3 for the early 0-type stars (Table 1).
The Luminous Stellar Content of 30 Doradus and NGC 3603 - The Nearest Visible Giant HII Regions
Authors: Moffat A.F.J. , Shara M.M. , Seggewiss W.
Published: June 2019

30 Dor in the LMC and NGC 3603 in the Galaxy are the nearest visible examples of similar giant (or even more massive supergiant) HII regions being studied in other more distant galaxies, where spatial resolution is a much more serious problem. Hence, understanding 30 Dor and NGC 3603 may provide important clues to understanding extragalactic giant HII regions in general.
Wolf-Rayet Stars in M31's OB Associations
Authors: Armandroff T.E. , Massey P. , Conti P.S.
Published: June 2019

It is well-known that the massive star population exerts a disproportionately great influence on the environment within a galaxy, especially through the ejection of chemically enriched material and the input of energy into the interstellar medium. In order to more fully understand the structure and evolution of galaxies, it is important to determine how the massive star content of a galaxy changes with Hubble type, galaxian luminosity and metallicity. Conversely, if our goal is to understand the evolution of massive stars, it is helpful to observe them in a variety of environments, as stellar wind properties should depend on chemical abundances. We are involved in a long-term project to survey the massive star population in a diverse sample of nearby galaxies. Unfortunately, it is extremely difficult to isolate a sample of relatively unevolved massive stars in an external galaxy, since the colors and absolute visual magnitudes of a 20 MO and 100 MO star are nearly identical, and can be further confused by differential internal extinction. Wolf-Rayet (WR) stars, however, are relatively easy to detect due to their strong emission-line spectra and high luminosities. Since WR stars are known to have evolved from 0 stars and because their space distribution in the solar neighborhood is identical to that of the most massive 0 stars, we have decided to use WR stars as tracers of the massive star population in nearby galaxies.
FeII in the UV Spectrum of Luminous Emission Line Stars
Authors: Muratorio G. , Friedjung M. , Viotti R.
Published: June 2019

Following the excessive mass loss rates we derived in a previous analysis of the FeII emission and absorption lines of some luminous Magellanic Clouds stars, assuming the two components formed in the same region (Muratorio et al., 1984), we again analysed the FeII data using the same method (Muratorio, 1985), but taking into account the presence of high velocity winds detected in some stars (R66, R126) by the study of the high dispersion IUE spectra (Stahl et al., 1983; Zickgraf et al., 1985).
Two Faint WC Stars near 30 Doradus
Authors: Morgan D.H. , Good A.R.
Published: June 2019

“Wolf-Rayet stars in the LMC: how faint do they go?” That was the title of a recent paper by Massey and Conti (1983) who found that the faintest WN star in Breysacher's (1981) catalogue of LMC WR stars has mv = 17.1. The faintest WC star in that catalogue is Br74 which has mv = 15.6. We have now detected two faint WC stars at mv 18.6, three magnitudes fainter than Br74.
Propagating Star Formation Induced by Superbubbles
Authors: Kafatos Minas , McCray Richard
Published: June 2019

A supernova explosion in the galactic disk creates a hot, low density cavity which persists much longer than typical lifetimes of supernova remnants. McCray and Snow (1979), Bruhweiler et al. (1980), Tomisaka, Habe and Ikeuchi (1980) and Kafatos et al. (1980) pointed out that repeated supernovae from a stellar association will produce an expanding shell of gas (R ≳ 100 pc) and offered extensive evidence for such shells -primarily in the form of H I shells.
On the Arm Pattern of M33
Authors: Ivanov Georgi Raikov , Kunchev Peter Z.
Published: June 2019

By comparison of U and B plates of M33 we extended the numerations of Humphreys and Sandage (1980) adding 54 new OB associations. The associations identified by HS are outlined with continuous line and ours are represented with dash on Figure 1. Many of the identified by us associations are near the nucleus of M33. Due to U plate used by us the background in the central region is fainter than that on the B plate and the associations are distinguished very well on U plate (Kunchev and Ivanov, 1984). Our associations of the outer region of M33 consist mainly of relatively fainter young B stars.
Luminosity Functions in Dwarf Irregulars
Authors: Hoessel John G.
Published: June 2019

Observing luminosity functions and color-magnitude diagrams is a first step towards understanding the luminous stellar populations in galaxies. Dwarf irregular galaxies are of special interest for a variety of reasons. They are common at distances where they can be resolved, and generally have low background surface brightnesses which makes photometry of the resolved stars relatively easy. Dwarf irregulars exhibit a fairly wide spread in metal abundance allowing the study of massive star formation and evolution under a variety of conditions. Also, the dynamics of such systems is in general simple, without spiral density waves or other effects which might complicate understanding of the star formation process.
The Dynamics of Open Clusters
Authors: Mathieu Robert D.
Published: June 2019

Many of the “observations” of dark matter involve the application of the virial theorem or more sophisticated dynamical models to bound gravitational systems. Such studies often adopt a certain mass function and assume that the system is in a state near equipartition. In many cases though the data are not sufficient to determine the mass function or justify the equipartition assumption. Open clusters provide excellent case studies of systems which are relaxed and which have a large observable stellar-mass range, approaching an order of magnitude in the nearest young clusters. As a result open clusters have recently been the subject of extensive dynamical study.
Differences in Mass Distribution for Field and Cluster Spiral Galaxies
Authors: Burstein David , Rubin Vera C.
Published: June 2019

Our group has now obtained rotation curves for 80 spiral galaxies, Hubble types Sa through Sd. As described in Rubin et al. (Ap. J. 289, 81; 1985), the forms of these rotation curves are similar for all Hubble types. Given this observational fact, we have chosen to analyze the mass distributions for these galaxies under the assumption that the mass distributions for all spirals can be described by the same three-dimensional form, here taken to be spherical for simplicity. The mass distribution forms for 71 of these galaxies can be placed into a simple classification scheme based on the curvature of mass distribution form in a log(radius) - log (integral mass) diagram. The three most common mass forms among this continuum are termed Types I, II and III, the forms of which are displayed below (see also the discussion by Rubin elsewhere in this Symposium).
The Ring of HI in LEO: Probing the Mass Distribution in a Galaxy Group
Authors: Schneider Stephen E. , Salpeter Edwin E. , Terzian Yervant
Published: June 2019

The intergalactic neutral hydrogen in the M96 group (Schneider et al. 1983) provides an unusual probe of the detailed mass distribution in a group of galaxies. Previous observations (Schneider 1985) tentatively suggested the existence of a large ring structure to the gas. Sensitive new observations made at Arecibo confirm that the intergalactic gas forms a 200 kpc diameter eccentric ring around the two central galaxies in the group, the giant elliptical galaxy NGC 3379 (M105) and the lenticular NGC 3384.
Dark Matter in Dwarf Galaxies
Authors: Kormendy John
Published: June 2019

This paper reviews the observational evidence for dark matter (DM) in dwarf spiral (dS) and dwarf spheroidal (dE) galaxies. The most secure detection of DM in dwarf galaxies is given by HI rotation curves. They provide estimates of DM halo parameters, i. e., isothermal core radii rc, central densities ρ0 and one-dimensional velocity dispersions σ. The smallest DM halo measured so far is in DDO 127 (MB = −14.5 for H0 = 75 km s−1 Mpc−1, rc ≃ 2.3 kpc, σ ≃ 27 km s−1). If this halo is made of neutrinos of mass mv, then phase-space constraints imply that mv > 110 eV. This is difficult to reconcile with cosmological upper limits giving Ω ≤ 1. Ultimately, dE galaxies will provide the strongest constraints on DM in dwarf galaxies; a detailed look at present results shows that they are not yet conclusive.
The Global Stability of our Galaxy
Authors: Sellwood J. A.
Published: June 2019

Many mass models of our Galaxy (see e.g. Schmidt 1985 for a review) assume the disc to be nearly axisymmetric. For consistency, therefore, no such model should possess gross non-axisymmetric instabilities. However, most attribute less than half the central attraction at the Sun to bulge and halo material - a situation where bar forming instabilities are frequently found (see e.g. Sellwood 1983).
Gravitational Channels and the Cosmological Constant A
Authors: Ishizawa T.
Published: June 2019

A new model of filamentary matter fields and voids is proposed. This is a gravitational version of the MIT bag model of hadrons (see a review of DeTar and Donoghue 1983). Bekenstein and Milgrom (1984) have first proposed a gravitational bag model. Their bag is closed but our bag, called a channel, is open.
Hydrogen Molecules and the Radiative Cooling of Pregalactic Shocks
Authors: Shapiro Paul R. , Kang Hyesung
Published: June 2019

When a pregalactic gas of H and He is heated and reionized, as by a shock wave occurring in the nonlinear collapse of density fluctuations or in the case of explosions in the IGM, the gas cools radiatively and recombines out of equilibrium. The temperature drops faster than the ions can recombine. When the temperature falls below 104K, the residual electron concentration is large enough, as a result, to form H− ions which form H2 molecules, via (H + e → H− + hν) and (H + H− → H2 + e). Molecules also form via (H+ + H → H2+ + hν) and (H2+ + H → H2 + H+). As a consequence, H2 can form with a sufficient concentration (∼10−3) to cool the gas further, by rot-vibrational line excitation and the formation process itself, to ∼102K. This has an important effect on the Jeans mass and fragmentation. We show some illustrative results below for the time-dependent cooling and non-equilibrium recombination and molecule formation. The three cases are as follows: (1) isochoric cooling at hydrogen number density 1 cm−3; (2) isochoric cooling at 3×107 cm−3; (3) isobaric cooling starting at initial density 1 cm−3. At high densities, molecular cooling is suppressed.
A Model for the Sequence of Elliptical Galaxies
Authors: Wyse Rosemary F. G. , Jones Bernard J. T.
Published: June 2019

We present a simple model for the formation of elliptical galaxies, based on a binary clustering hierarchy of dark matter, the chemical enrichment of the gas at each level being controlled by supernovae. The initial conditions for the non-linear phases of galaxy formation are set by the post-recombination power spectrum of density fluctuations. We investigate two models for this power spectrum - the first is a straightforward power law, |δk|2 ∝ kn, and the second is Peeble's analytic approximation to the emergent spectrum in a universe dominated by cold dark matter. The normalisation is chosen such that on some scale, say M ∼ 1012M⊙, the objects that condense out have properties - radius and velocity dispersion - resembling ‘typical’ galaxies. There is some ambiguity in this due to the poorly determined mass-to-light ratio of a typical elliptical galaxy — we look at two normalisations, σ1D ∼ 350kms−1 and σ1D ∼ 140kms−1. The choice determines which of Compton cooling or hydrogen cooling is more important during the galaxy formation period. The non-linear behaviour of the perturbations is treated by the homogeneous sphere approximation.
Bimodal Star Formation and Remnant-Dominated Galactic Models
Authors: Larson Richard B.
Published: June 2019

Current data on the luminosity function of nearby stars allow the possibility that the stellar initial mass function (IMF) is double-peaked and that the star formation rate (SFR) has decreased substantially with time. It is then possible to account for all of the unseen mass in the solar vicinity as stellar remnants. A model for the solar neighborhood has been constructed in which the IMF is bimodal, the SFR is constant for the low-mass mode and strongly decreasing for the high-mass mode, and the mass in remnants is equal to the column density of unseen matter; this model is found to be consistent with all of the available constraints on the evolution and stellar content of the solar neighborhood. In particular, the observed chemical evolution is satisfactorily reproduced without infall. The total SFR in the model decreases roughly with the 1.4 power of the gas content, which is more plausible than the nearly constant SFR required by models with a monotonic IMF.
Observational Searches for Dark Halos
Authors: van der Kruit P.C.
Published: June 2019

A review of observational searches reveals the following constraints for the constituents of dark halos: (1) Optical searches show that these halos are not for a large fraction of their mass made up of dwarfs of spectral type M5 or earlier. (2) K-band (2.2 μ) searches virtually rule out all H- burning Main Sequence stars. (3) IRAS upper limits are consistent with black dwarfs of any age or Jupiters. (4) The inferred metallicity and M/L variations in the spheroid of NGC 7814 are consistent with the hypothesis that the dark matter consists of low mass objects that formed along with the luminous population II.
Use of the University of Toronto Southern Observatory as support for large-telescope and satellite programmes
Authors: Garrison R. F.
Published: June 2019

With a 60-cm telescope at an outstanding site, it is possible to coordinate observations with larger telescopes and with satellites to provide monitoring of interesting objects. The University of Toronto Southern Observatory at Las Campanas, Chile, has been involved in several such programmes, in support of large telescopes at Tololo, La Silla, and Mauna Kea, in addition to the I.U.E., EXOSAT, and other satellites.
Automatic photoelectric telescopes: status and potentials
Authors: Crawford David L.
Published: June 2019

Automatic photoelectric telescopes now exist. They are currently doing precision photometry of variable stars, fully automatically. More such telescopes will exist in the near future, and they will be doing automatic photometry of all sorts.
The main features of the 1.56-m telescope and its status quo
Authors: Lai Wan , Neng-hong Zhu , Lan-juan Wang , Zheng-hua Yang , Yi-jin Zheng
Published: June 2019

This telescope was designed for determining the trigonometric parallaxes of faint stars. The otpical configuration is a Ritchey-Chrétien system and has only a f/10 Cassegrain focus for photographic work.

The mounting is a combination of fork and yoke frame which can reduce the flexure due to gravity. A high speed digital servo-system was adopted for controlling and driving the telescope. At present some photographs of Comet Halley have been obtained.
Interacting binaries: an excellent project for small telescopes
Authors: Plavec Mirek J.
Published: June 2019

Discussed are meritorious projects for small and moderate telescopes in the field of interacting binaries with non-degenerate component stars. These interacting binaries are undergoing a mass transfer process, as a consequence of which the mass-accreting star may be partly or completely hidden in an accretion disk, and the system may be shrouded in dense clouds of circumstellar matter. This makes the observation, interpretation and modeling difficult; but it is important to study these “bizarre” binaries since they tell us a lot about stellar evolution in binary systems. Needed are various observations: Timing of eclipses; observation and re-observation of light curves in several colors (in uvby rather than in UBV; and in the red and infrared); radial velocity studies; spectrophotometry of crucial regions of the spectrum. As examples for these needs, the following systems are discussed in some detail, and their problems revealed: RX Cassiopeiae, W Serpentis, and W Crucis as examples of the strongly interacting systems (W Serpentids); U Sagittarii as a helium-rich binary in a rare evolutionary stage, which will be better understood if we decide whether the star eclipses or not; and KX Andromedae as a representative of non-eclipsing interacting binaries and of Be and shell stars, which may or may not be binaries.
Recent trigonometric parallaxes from two hemispheres
Authors: Ianna Philip A.
Published: June 2019

Both southern and northern hemisphere parallax results are reported for a number of stars including several white dwarfs, the central star of NGC7293, Barnard's star, and several other red dwarfs. The 1 meter astrometric reflector of the McCormick Observatory is described and some preliminary results are briefly discussed.
The Monash University Observatory: equipment and research
Authors: Innis J. L. , Thompson K. , Coates D. W.
Published: June 2019

The Monash Observatory, located at Mount Burnett, Victoria, seventy kilometres east of the city of Melbourne, at a latitude of 38° S has a 0.45-m Cassegrainian and a 0.25-m Newtonian telescope. Both are equipped for photoelectric photometry, with microcomputer-based data logging systems. The 0.45-m has recently replaced the observatory's original 0.4-m Newtonian. Our site is near the coast, and has less than 20% photometric weather. Access to the telescopes and facilities of Mount Stromlo and Siding Spring Observatories (MSSSO) increases our observing time and the scope of our research. For a description of the Monash Observatory at mid-1984 see Coates et al, (1984).
Photometric research with a small telescope (Bamberg 37-cm. refractor) at Bosscha Observatory, Indonesia
Authors: Malasan Hakim L. , Okazaki Akira , Yamasaki Atsuma , Hadiyanto Gregorius
Published: June 2019

In 1979 Partoharsodjo (see Kitamura et. al., 1985) constructed a new photoelectric photometer with an RCA IP21 photomultiplier, so that it: 1) can be coupled easily with the Bamberg 37-cm. refractor at the Bosscha Observatory, and 2) can be used both for direct current and photon counting modes. Since its installation at the telescope in the early 80's, photometric work at Bosscha Observatory was resumed.
Cassegrain echelle spectroscopy with small telescopes
Authors: Hearnshaw J. B.
Published: June 2019

This paper comments on the growing use of cassegrain échelle spectrographs for high resolving power astronomical spectroscopy over the last two decades. Some of the theoretical and practical advantages of échelle spectrographs are outlined, as well as some of the problems that arise in their use. Design parameters of some recent échelle spectrographs in various observatories are summarised. A novel use of échelle spectrographs without a cross-dispersing element for radial velocity spectrometry is proposed. The design parameters of a fibre-fed échelle spectrograph that will achieve a resolving power of about 7 × 104with a 2 arc second input from a 1m telescope are outlined.