bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between the system of Astronomical constants and the radar determinations of the Astronomical Unit
Authors: Muhleman D. O.
Published: July 2016

This paper is devoted to an exact discussion of the determination of the astronomical unit with radar and to an extensive error analysis of the technique. Theoretical relationships between the constants are used to construct a consistent set of numerical values of constants based on these results.
A one-dimensional self-gravitating stellar gas
Authors: Lecar M.
Published: July 2016

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.
On spherical self-gravitating systems
Authors: Bouvier P.
Published: July 2016

Isolated spherical and self-gravitating systems are considered, within which dynamical mixing of the orbits has led to a steady state characterized by a given density law. The different possible corresponding distribution functionsf(E, A2) are obtained by solving a double integral equation through a power series inA2. Retaining only a finite number of terms of this series, some insight can be gained into the various types of anisotropy which can occur in the velocity distribution.
The structure of barred spirals
Authors: Prendergast K.
Published: July 2016

Orbits of stars in a barred spiral have been calculated. It was found that stars with high velocity escape from the system. Stars with intermediate velocities move along the bar and at the same time oscillate perpendicularly to it, until they reach the end of the bar; then they describe almost circular orbits around the axis of rotation, being eventually recaptured by this or the other end of the bar. Thus theΘ-form galaxies may be explained. Lowvelocity stars either remain always near the origin or escape from the ends of the bar forming trailing arms. The hydrodynamics of the barred spirals has also been studied. A circulation in the bar in the direction of rotation was found. A stationary shock-wave is formed, which explains the existence of some dark lanes in barred spirals.
On the determination of the oscillation frequencies in the meridian plane of galactic stellar orbits
Authors: Ollongren A.
Published: July 2016

First a review is given of the general properties of orbits belonging to one family computed by numerical integration. Then the method by which it is possible to derive the ratio of frequencies of oscillation of an orbit which is topologically equivalent to a Lissajous figure is explained. It is shown that the assumption that the ratio of oscillations is a constant must be regarded as a first approximation. In a second approximation this ratio is taken to be variable.

The discussion of the orbital inclinations during passage of the galactic plane for the computed orbits, suggests a periodic form for this variability, which would explain the occurrence of the main types of orbits found.
Numerical exploration of the restricted three-body problem
Authors: Hénon M.
Published: July 2016

A number of orbits have been computed in the plane restricted three-body problem; the two main bodies have the same mass and move on a circular orbit. By consideration of the successive intersections of the orbit with thexaxis, the problem can be reduced to the study of a plane area-preserving mapping. A second integral, distinct from Jacobi's integral, seems to exist inside given ranges of initial conditions, but not outside. The general picture is quite similar to the one found in the problem of the third integral of galactic motion. Extension of this work to other values of the mass ratio is under way.
Three-body problem and elliptic integrals
Authors: Schmeidler F.
Published: July 2016

In an earlier paper (1) it was shown that there are certain cases in the three-body problem in which all perturbations of the first order can be represented by elliptic integrals. Some more cases of such sort are outlined here.
On nearly-commensurable periods in the restricted problem of three bodies, with calculations of the long-period variations in the interior 2:1 case
Authors: Message P. J.
Published: July 2016

An analytical discussion of that case of motion in the restricted problem, in which the mean motions of the infinitesimal, and smaller-massed, bodies about the larger one are nearly in the ratio of two small integers displays the existence of a series of periodic solutions which, for commensurabilities of the typep+ 1:p, includes solutions of Poincaré'sdeuxième sortewhen the commensurability is very close, and of thepremière sortewhen it is less close. A linear treatment of the long-period variations of the elements, valid for motions in which the elements remain close to a particular periodic solution of this type, shows the continuity of near-commensurable motion with other motion, and some of the properties of long-period librations of small amplitude.

To extend the investigation to other types of motion near commensurability, numerical integrations of the equations for the long-period variations of the elements were carried out for the 2:1 interior case (of which the planet 108 “Hecuba” is an example) to survey those motions in which the eccentricity takes values less than 0·1. An investigation of the effect of the large amplitude perturbations near commensurability on a distribution of minor planets, which is originally uniform over mean motion, shows a “draining off” effect from the vicinity of exact commensurability of a magnitude large enough to account for the observed gap in the distribution at the 2:1 commensurability.
The orbit of Pluto over a long interval of time
Authors: Brouwer D.
Published: July 2016

The paper presents a summary of the results obtained by C. J. Cohen and E. C. Hubbard, who established by numerical integration that a resonance relation exists between the orbits of Neptune and Pluto. The problem may be explored further by approximating the motion of Pluto by that of a particle with negligible mass in the three-dimensional (circular) restricted problem. The mass of Pluto and the eccentricity of Neptune's orbit are ignored in this approximation. Significant features of the problem appear to be the presence of two critical arguments and the possibility that the orbit may be related to a periodic orbit of the third kind.
Sur la theorie du mouvement d'un satellite a fortes inclinaison et excentricite
Authors: Kovalevsky J.
Published: July 2016

L'auteur montre comment on peut éliminer les termes à courte période de la théorie du mouvement d'un satellite perturbé par le Soleil, en ne faisant aucun hypothèse sur la valeur de l'excentricitéeet de l'inclinaisoni.Les seuls développements sont selon les puissances dem=v/net celles du produitem.On donne une interprétation des résultats obtenus pour les premières puissances dem.
Comparing Optical and Radio — Quantum Issues
Authors: Nityananda Rajaram
Published: July 2016

Once upon a time, there were radio and optical astronomers, each group with its own way of detecting and thinking about radiation. In spite of the shock treatment administered by Hanbury-Brown and Twiss more than thirty five years ago, this dichotomy persists to a surprising extent even today. As new techniques emerge, we clearly need to do better. Coherent and incoherent detection, heterodyning and interferometry are all situations where a full analysis involves quantum behaviour of the radiation. This informal review covers the general approach needed and goes over some points of principle which arise.
Heterodyne Interferometry in the Infrared
Authors: Townes C.H. , Bester M. , Danchi W.C. , Degiacomi C.G. , Greenhill L.J.
Published: July 2016

The University of California Infrared Spatial Interferometer (ISI) for the 10 μm wavelength region is briefly described along with results obtained on prominent stars and on atmospheric phenomena. The system has two movable telescopes of 1.65 m aperture. It operates in principle like a modern radio interferometer, using heterodyne detection, CO2 laser local oscillators, RF delay lines, and lobe rotation to maintain a fixed-frequency fringe rate.

Rather extensive measurements have been made on atmospheric pathlength or phase fluctuation characteristics which show substantial deviations from the Kolmogorov-Taylor model, fortunately in a direction favoring adaptive optics, long baselines, and the use of infrared wavelengths. Outer scales as small as about 10 meters occur under good seeing conditions. Visibility results on 13 stars show that 6 of them have dust shells rather far from the star and give evidence for episodic emission of gas. Others of the 13 stars also vary with time, but are characterized by more continuous emission and dust formation near the stars at temperatures as high as 1300 K.
The SAO Submillimeter Wavelength Array
Authors: Moran James M.
Published: July 2016

The SAO Submillimeter Wavelength Array is under construction and is expected to be ready for observations in 1997. It will consist of six telescopes with baselines from 9 to 470 m and resolutions as fine as 0″.1. Eight receivers will cover all bands from 180 to 900 GHz in linear polarization; two orthogonal polarizations will be available at 350 GHz. Multiyear site testing on Mauna Kea shows that the precipitable water vapor is less than 1 mm for 17% of the time, and the rms phase fluctuations on a baseline of 100 m are less than 55 μm for 25% of the time. The configuration of the array will be optimized to provide nearly uniform coverage in the uv plane. The correlator spectrometer will have 105 spectral channels (8192 per baseline) and will be able to provide 0.6 MHz resolution for a total bandwidth of 4 GHz.
Imaging Techniques: Limitations to the Quality of Images
Authors: Cornwell T. J.
Published: July 2016

Our ideas of how to image objects have progressed by leaps and bounds in the last twenty to thirty years. We now have a sophisticated understanding of many clever and subtle approaches to imaging. There are a few outstanding contributions which have provoked flurries of development and acheivement in many different areas: top of my list would be the principle of aperture synthesis, Jennison's closure phase, Högbom's CLEAN algorithm and Labeyrie's speckles. In addition, we have benefited tremendously from developments in computing hardware, software and algorithms (the most spectacular being the Cooley-Tukey Fast Fourier Transform). Each one of these contributions did not so much spur development in existing areas as open up entirely new vistas of possibilities. For example, Jennison's closure phase is rarely directly used by radio-interferometrists now but it did show, particularly when developed in VLBI, that imaging in the presence of severe phase errors is possible. This success then encouraged the two separate developments. First in the more flexible selfcalibration routines in which closure is implicit and, second, in pushing imaging interferometric arrays to shorter and shorter wavelengths, now ending up in the infra-red and optical regimes. Following on from these great works, many people have made lesser but still vital contributions. The example of speckle comes to mind as one where many people have had a hand in determining what is now standard technique.
Beam Combination for Wide Field Imaging
Authors: Tallon M. , Tallon-Bosc I.
Published: July 2016

Several limitations reduce the field of view in radio-interferometry. With an optical array, two of them can be overcome to some extent according to the beam combination method. A beam combination in the pupil plane can completely overcome one of them. In the image plane, a beam combination obeying the rules of geometrical optics can overcome both limitations in principle, but is difficult to achieve in practice. We discuss particularly the real case of a Michelson Stellar Interferometer where a periscope partially re-introduces these limitations, yielding a trade-off between the extension of the field of view and the use of the periscope.
Direct Maximum-Entropy Image Reconstruction from the Bispectrum
Authors: Buscher D.F.
Published: July 2016

The strategies for image reconstruction from optical synthetic-aperture data can be divided into two camps according to their historical legacies: those coming from the field of more conventional optical image processing, where the data are relatively complete in terms of Fourier coverage, have concentrated on trying to recover images using “brute force” methods. They make use of the massive size of the typical datasets to try and derive an image without having to use any a-priori constraints. The size of the datasets to some extent restricts the algorithms used towards being as simple and hence fast as possible. Radio-astronomical imaging strategies, on the other hand, have always been designed to cope with sparse and missing data, and many sophisticated algorithms have been designed to make maximum use of a-priori constraints with iterative global fitting techniques.
Progress on GI2T
Authors: Tallon-Bosc I. , Bonneau D. , Labeyrie A. , Morand F. , Mourard D. , Stee P. , Vakili F.
Published: July 2016

The purpose of this paper is to describe the operation of GI2T, the visible Michelson stellar interferometer with two 1.5 m apertures, as well as a presentation of its desired evolution.
The Baseline Metrology System of the USNO Astrometric Interferometer
Authors: Elias Nicholas M. , Hutter Donald J.
Published: July 2016

The USNO Astrometric Interferometer (USNOAI; a subarray of the Navy Prototype Optical Interferometer at Lowell Observatory) is presently under construction and expected to begin limited operations within a year. The main goal of the USNOAI observations is to provide a northern hemisphere catalog of several thousand stars with positions known to a few mas. In order to meet this requirement, a baseline laser metrology system must be employed to measure the three-dimensional motions of the baselines with an accuracy better than ~ 0.1 μm. The metrology scheme, as presently conceived, represents the largest and most complex high-resolution laser metrology system ever attempted.
Speckle Imaging with the Bispectrum and Without Reference Star
Authors: Thiebaut E.
Published: July 2016

A technique for reconstructing diffraction-limited image of an object from speckle images without reference star is applied to both simulated and real data. The object spectrum is estimated by blind deconvolution using the power spectrum of the speckle images and the phase is restored from the bispectrum.
Generalized Versus Classical Maximum Entropy for Imaging
Authors: Bajkova A.T.
Published: July 2016

The problem of image reconstruction from incomplete and noisy complex Fourier spectrum is considered. The maximum entropy method (MEM) is of great interest as the most effective nonlinear reconstruction method having superresolution effect. Because objects of radio astronomical observations are incoherent radio sources described by real non-negative distributions, application of the classical MEM is quite reasonable. But it is established that the MEM gives acceptable reconstruction quality mostly in the case of point-like sources and in general it does not ensure satisfactory reconstruction of continous, graytone objects, which can considerably restrict applications of the MEM in astronomy. The generalized maximum entropy method (GMEM) was originally proposed for reconstruction of distributions described by complex functions (Bajkova, 1992) and was considered as having the same properties of the classical MEM. More careful analysis of the GMEM and classical MEM for real non-negative objects allowed to establish that the GMEM ensures much more exact reconstruction, especially in the case of continous objects. Explanation and demonstration of this interesting and very important phenomenon is the purpose of the present paper.
Adaptive Optics: Performance and Limitations
Authors: Roddier Francois
Published: July 2016

Adaptive optics systems are now being developed for astronomical applications. On large telescopes, a substantial image improvement can be obtained in the near infrared, using natural guide stars.
High Resolution Imaging Forty Years Ago
Authors: Jennison R. C.
Published: July 2016

This conference is concerned with the very high resolution imaging of cosmic sources in many parts of the electromagnetic spectrum. Various techniques are now available and the equipment is often automated and highly sophisticated but the term ‘very high angular resolution’ is comparative. Many of the problems existed over forty years ago when the best resolving power was about half a degree and the two major radio ‘stars’ appeared to be point sources. Very high resolution imaging in those days was the struggle to reach one minute of arc and Hanbury Brown had set his sights on considerably better than one second of arc with the concept of the intensity interferometer. The dream was to achieve a resolving power comparable to that of optical telescopes.
First Experimental Results from Pupil Masking on a Solar Telescope
Authors: Restaino Sergio R. , Radick Richard R. , Loos Gary C.
Published: July 2016

We present the results of a pupil masking experiment using the Sun as a source. The goal of the experiment was a first proof of concept validation for Fizeau interferometric beam combination using a source that fills the field of view of the telescope. Phase diversity techniques are employed to record the phasing errors in the mask required to construct the optical transfer function (OTF) and are used to deconvolve the dirty images.
An Interferometric Survey of Mira Variables and M Supergiants
Authors: Tuthill P.G. , Haniff C.A. , Baldwin J.E.
Published: July 2016

We present preliminary results from an imaging survey of bright northern Mira variables and Supergiants. Diffraction-limited images of Mira exhibit the same elongation along PA 120° as observed in previous observations. Of the other Mira variables observed, R Cas is unambiguously detected as non-spherically symmetric. Our observations of α-Her are consistent with there being a ‘hot-spot’ on its surface, similar to those we have previously detected on Betelgeuse.
High Resolution Interferometric Observations of Eclipsing Binary Stars
Authors: Pan Xiaopei , Shao Michael , Colavita M. Mark
Published: July 2016

Eclipsing binary stars are of great importance in astronomy. Now, high angular resolution measurements of eclipsing stars with the Mark III Stellar Interferometer (Shao 1988) can determine not only all of the orbital parameters, but also the luminosities and color indices of the two components, and can yield precise information for the study of the stellar evolution models. Particularly, the combination of interferometric and photometric results provide a direct measurement of stellar effective temperature. In the case where the primary component can be resolved, the results from the optical interferometer then provide a reliable determination of the absolute system parameters. In addition, eclipsing binary stars are good candidates for comparison of different techniques, i.e., interferometric, photometric, astrometric, and spectroscopic, and for checking whether systematic uncertainties exist with certain techniques.
Lunar Occultations of Young Stellar Objects in the Taurus and Ophiuchus Star Forming Regions
Authors: Richichi A. , Haas M. , Leinert Ch. , Jameson R. , Adams D. , Zinnecker H.
Published: July 2016

We have carried out lunar occultation observations at λ = 2.2μm at the WHT and Calar Alto telescopes of young stellar objects both in the Taurus and the Ophiuchus star forming regions. We report the discovery of 4 new binary systems: IW Tau and HK Tau/G2 in Taurus as well as GSS 35 and VSSG 14 in Ophiuchus; the projected separations are about 70 milliarcseconds (mas) for each of the Taurus objects, while for the Ophiuchus sources they are about 20 and 100 mas, respectively (20 mas correspond to 3 AU).
Progress of the Optical Very Large Array
Authors: Labeyrie A. , Mourard D. , Morand F. , Arnold L. , Dejonghe B. , Dejonghe J. , Cazale C. , Lemaitre G. , Vernet D. , Blazit A. , Texereau J. , Kessis J. , Rambaut J. P.
Published: July 2016

The construction of a prototype telescope is now reaching the stage of mirror polishing and building the active cell. Three blanks have already been produced. Two polishing methods are tested, utilizing the stressing technics, or involving excentered polishing strokes. A working model of one leg of the telescope translator has been built.
The Cosmological Application of Very High Angular Resolution in Radio Astronomy
Authors: Gurvits L. I.
Published: July 2016

An approach providing an estimate of the cosmological deceleration parameter qo from VLBI survey data is described.
The Nature and Fate of the Sagittarius Dwarf Galaxy
Authors: Ibata R.A.
Published: July 2016

The Sagittarius dwarf galaxy, located at a distance of ~ 15 kpc behind the Galactic bulge, is in the process of being tidally disrupted and assimilated into the Milky Way. This unique event allows the physics of galactic merging to be probed in unprecedented detail, and may shed light on the hypothesized population of primordial galaxies that merged to form the Milky Way.
Are the Bulge C-Stars Related to the Sagittarius Dwarf Galaxy?
Authors: Ng Yuen Keong
Published: July 2016

When the Sagittarius dwarf galaxy (SDG) crosses the galactic plane star formation might occur in its tidal tail. Carbon stars, due to their brightness, are ideal tracers for such an event. Ng & Schultheis (1997) suggested that the Bulge carbon stars (Azzopardi et al. 1991; ALRW) might be at SDG's distance. In the galactic Bulge these stars are completely different from carbon stars found in the LMC, SMC and dwarf spheroidal galaxies. If one keeps these stars in the Bulge and tries to explain their properties through a binary evolution scenario, one has to explain why they are not found up to the red giant branch tip: there is a discrepancy. Ng (1997) argues that part of the mystery concerning the luminosity of the ALRW stars would be solved if they are related to the SDG. It is demonstrated that the carbon star sequence is in that case similar to the observed SMC sequence. The carbon stars are in that case not metal-rich as previously thought, but they have a metallicity comparable to the LMC, with an age between 0.1–1 Gyr. A significant fraction of the carbon stars still have luminosities fainter than the lower LMC limit of . A similar trend is present among carbon stars found in other dwarf spheroidals. A scenario through binary evolution is assumed for these stars, because TP-AGB models cannot explain their origin through a single-star evolution scenario, even if they form immediately after entering the TP-AGB phase.
An HI Search for M81 Group Dwarf Galaxies
Authors: Van Driel W. , Kraan-Korteweg R.C. , Binggeli B. , Huchtmeier W.K.
Published: July 2016

The M81 group has great advantages for dwarf galaxy studies: it has about three times the dwarf content of the Local Group but is at only about a quarter of the Virgo cluster distance. We searched for HI in 23 optically selected dwarf members and possible members of the M81 group with the Nançay decimetric radio telescope in the velocity range of −529 to 1826 km s−1 with considerably better sensitivity (2–4 mJy rms.) than previous surveys. Half the objects observed are irregular dwarfs, expected to be HI-rich and detectable at Nançay if at the distance of the M81 group (4 Mpc).
Galaxy Interactions: The HI Signature
Authors: Sancisi R.
Published: July 2016

HI observations are an excellent tool for investigating tidal interactions. Ongoing major and minor interactions which can lead to traumatic mergers or to accretion and the triggering of star formation, show distinct HI signatures. Interactions and mergers in the recent past can also be recognized in the HI structure and kinematics. Recent 21cm line surveys of large samples of galaxies indicate that at least one out of every four galaxies shows signs of a present interaction or merger/accretion events in the recent past.
Galaxy Interactions in the Local Volume
Authors: Karachentsev I.D. , Makarov D.I.
Published: July 2016

Imaging of a large number of faint galaxies with the Hubble Space Telescope reveals a significant excess of interacting and peculiar objects among them (Griffiths et al., 1994, Burkey et al., 1994). Being expected in general, this result needs, however, to be expressed quantitatively. To estimate evolutionary changing of the relative number of interacting galaxies, δint(z), from their redshift z, one must determine reliably the local value, δint(0). But due to a subjective manner of definition of interacting galaxy system, the published values of δint(0) differ from one author to another several times. The most appropriate sample to estimate δint(0) would be quite a representative sample of very nearby galaxies, which is restricted by their distance or radial velocity. Below we consider data on such a fair sample, named the Local Volume (=LV), which is the most complete one at the present moment.
Radio Continuum Observations of NGC 1961: Interaction with the Intergalactic Medium or the Remnant of a Merger?
Authors: Lisenfeld U. , Alexander P. , Pooley G.
Published: July 2016

We present new radio continuum images of the supermassive, peculiar galaxy NGC 1961 at 1.5, 4.9, 8.4 and 15 GHz. NGC 1961 (Arp 184) is a very massive (dynamical mass > 1012M⊙) Sb galaxy with a peculiar and asymmetric optical appearance. Furthermore, it exhibits an unusual, asymmetric HI distribution with an extensive wing of gas extending 30 kpc to the north-west and a sharp edge to the south-east (Shostak et al. 1982).
Star Formation in Collisions Between Two Gas-Rich Disk Galaxies
Authors: Struck Curtis
Published: July 2016

We present the results of a modest grid of three-dimensional (SPH) simulations of nearly head-on collisions between two model galaxies, each consisting of a rigid halo and a gas-rich disk component. The companion to primary mass ratio used is typically 0.2 - 0.35. Simple models of radiative cooling and heating from young star activity are also included in the simulations. Star formation is assumed to occur when the local gas density exceeds a threshold value. In these collisions the primary gas disk remains largely intact, though a gas bridge is splashed out between the two galaxies. Star formation occurs in asymmetric ring-like waves in the primary. The bridge is predicted to have essentially no ongoing star formation. These results agree with observations of the Cartwheel and VII Zw 466 ring galaxies.
The Structure of Merger Remnants of Compact Groups of Galaxies: Some Preliminary Results
Authors: Athanassoula E. , Vozikis Ch. L.
Published: July 2016

We present some preliminary results on the properties of multiple merger remnants. We discuss their axial ratios, theirV/σ ratio as a function of ellipticity, and their circular velocity profiles.
Mass Distribution of the E0 Galaxy NGC 6703 from Absorption Line Profile Kinematics
Authors: Gerhard O.E. , Jeske G. , Saglia R.P. , Bender Ralf
Published: July 2016

Absorption line velocity profiles (vps) contain important information on the anisotropy and mass distribution of elliptical galaxies (e.g., Gerhard 1993, Merritt 1993). Here we briefly present results of an extensive analysis of the E0 galaxy NGC 6703 (Gerhard et al. 1997). This work is part of an observational and theoretical program aimed at understanding the orbit structure and dark matter content of ellipticals at intermediate radii (a preliminary account is given in Saglia et al. 1997).
Star-Forming Activity in Arp-Madore Galaxies
Authors: Hopkins A.M. , Cram L.E.
Published: July 2016

The rate of star formation is enhanced in many galaxies that show disturbed morphology and/or evidence of interaction. However, the physical explanation of this connection has proved elusive, since it appears that peculiar morphology of a specific type is neither necessary nor sufficient to promote star formation. To explore the relation between star formation rates and galaxy morphology we have selected a sample of galaxies from the Arp-Madore Catalogue of Southern Peculiar Galaxies and Associations (AMC) and the Principle Galaxy Catalogue (PGC), and estimated their star formation rate using the far-infra-red (FIR) power listed in the QMW IRAS Galaxy Catalogue (QMCIGC). There are 933 objects common to all three catalogues, potentially providing the necessary data for the peculiar galaxies.
Luminous Infrared Galaxies in a Merging Sequence: ISO Observations
Authors: Hwang C.-Y. , Lo K.Y. , Gao Y. , Gruendl R.A. , Lu N.-Y.
Published: July 2016

We report mid-infrared images of several luminous infrared galaxies (LIGs) taken with ISOCAM on the Infrared Space Observatory (ISO). These LIGs were chosen to represent different phases of a merger sequence of galaxy-galaxy interaction with special emphasis on early/intermediate stages of merging. The molecular gas distribution of these LIGs has also been mapped at high spatial resolution (see contribution by Gao et al., this volume). The goal is to do a synoptic study of the evolution of physical conditions in these LIGs along the merger sequence.
Interactions, Mergers, and QSO Activity
Authors: Stockton Alan
Published: July 2016

Is QSO activity sometimes triggered by interactions or mergers of galaxies? Are all QSOs the result of interactions or mergers? Such questions, arising explicitly in the late 1970s, had their roots in the well-known Stoking the Furnace? section of Toomre & Toomre (1972), the Feeding the Monster paper of Gunn (1979), and the early observational evidence that weaker forms of nuclear activity, such as Seyferts, seemed often to be found in interacting systems (e.g., Adams 1977). Reviews of the evidence regarding the relation of interactions and mergers to QSO activity have been given by Stockton (1990) and Heckman (1990). Some of the more important developments since these reviews are:
Relics of Nuclear Activity: Do All Galaxies Have Massive Black Holes?
Authors: van der Marel Roeland P.
Published: July 2016

The distribution of black hole (BH) masses M• in galaxies is constrained by photometric and kinematic studies of individual galaxies, and by the properties of the quasar population. I review our understanding of these topics, present new results of adiabatic BH growth models for HST photometry of elliptical galaxies with brightness profiles of the ‘core’ type, and discuss the implications of ground-based stellar kinematical data. It is not yet possible to uniquely determine the BH mass distribution, but the available evidence is not inconsistent with a picture in which: (i) a majority of galaxies has BHs; (ii) there is a correlation (with large scatter) between M• and spheroid luminosity Lsph of the form M• ≈ 10−2Lsph (solar B-band units); and (iii) the BHs formed in a quasar phase through mass accretion with efficiency ε ≈ 0.05.
ASCA Observations of Luminous Infrared Galaxies: Evolution from Starburst to AGN?
Authors: Nakagawa Takao , Kii Tsuneo , Fujimoto Ryuich , Miyazaki Toshiyuki , Inoue Hajime , Ogasaka Yasushi , Arnaud Keith , Kawabe Ryohei
Published: July 2016

One of the most important results of the IRAS survey is the discovery of a class of “Luminous Infrared Galaxies” (LIGs), which emit most of the energy in the infrared and are the dominant population in the local universe at luminosities above 1011L⊙ (e.g., Sanders & Mirabel 1996). All LIGs appear to be extremely rich in molecular gas, and many of them show evidence of recent interacting/merging activities. Hence it is now accepted that strong interactions of gas-rich galaxies triggers large central concentration of molecular gas, and makes optimal conditions for both enormous nuclear starbursts and building and/or fueling AGN. Actually, various observations show evidence of starburst activity as well as that of AGN in many LIGs (Sanders & Mirabel 1996).
The Host Galaxies of IR Luminous Quasars
Authors: Clements D.L. , Baker A.C. , Lidman C.J.
Published: July 2016

A connection is suspected between quasars and ultraluminous IR galaxies (ULIRGs). Almost all ULIRG activity is triggered by mergers (e.g. Clements et al. 1996, MNRAS, 279, 477). We thus investigate the relationship between quasars and ULIRGs by examining the relationship between FIR luminosity and host morphology in quasars. We use the z < 0.3 imaging survey of PG quasars by McLeod & Rieke (1994, ApJ, 420, 58; 431, 137), and ancillary data, to determine which quasars in the survey have disturbed hosts. This is combined with FIR data from Sanders et al. (1989, ApJ, 347, 29). We apply Survival Analysis techniques to see if the FIR luminosity of the disturbed and undisturbed host quasars differ. We find, with 99.99% confidence, that the disturbed host quasars have higher FIR luminosity. We observe a small, but complete, sample of six quasars selected to have LFIR > 1011.8L⊙, and a comparison sample of quasars with similar redshifts and B-band absolute magnitudes, but without detected FIR emission. At least 3 of the FIR luminous quasars are found in disturbed hosts while the non-FIR luminous quasars all lie in undisturbed hosts. The FIR luminosity in ULIRGs is triggered by interactions. If ULIRGs evolve into quasars we would expect FIR luminous quasars to be younger, and to share more characteristics with ULIRGs, especially disturbed host morphology. These studies are consistent with this model for quasar evolution.
The Nature of Ultraluminous IRAS Galaxies
Authors: Clements D.L. , Sutherland W.J. , McMahon R.G.
Published: July 2016

We present the results of a continuing programme to investigate the properties of the Ultraluminous IRAS Galaxies (ULIRGs) in a large sample selected from the IRAS Faint Source Catalogue and identified with the APM galaxy catalogue (for details of the survey selection and initial results see Clements et al. 1996, MNRAS, 279, 459). Observations now include optical imaging for a complete subsample to BJ = 19.5 (Clements et al. 1996, MNRAS, 279, 477) and near-IR imaging for a complete subsample to BJ = 19 (Clements et al. in preparation). Moderate resolution optical spectroscopy, ISOPHOT photometry and ISOSWS spectroscopy have also been obtained for smaller subsamples of this survey. New redshift measurements have identified 11 new ULIRGs, extending the sample size to 102 ULIRGs. These observations have extended the maximum redshift to 0.44, and have also discovered a new broad-line ULIRG at z = 0.351. Initial analysis of our ISOPHOT data, while subject to substantial calibration uncertainties, shows a broad range of 160–120μm flux ratios which might indicate the presence of cold dust (T ~ 20 K) in some objects. Such dust would not have been detectable by IRAS. Our continuing multiwavelength studies of ULIRGs will be used to examine the nature of the power source in these objects, and their relationship to other extragalactic populations.
The Interplay Between the Nuclear Bars, Central Starburst, and Remarkable Outflow in NGC 2782
Authors: Jogee S. , Kenney J.D.P. , Smith B.J.
Published: July 2016

We show that the nearby peculiar interacting galaxy NGC 2782 (Arp 215) harbors a clumpy molecular CO bar. The gas bar has a radius of ~7.5″ (1.3 kpc), a mass of ~ 2.4 × 109M⊙, and leads a nuclear stellar bar of similar extent (Jogee et al. 1997b). We estimate the gravitational torque exerted by the nuclear stellar bar and find large gas inflow rates (≫ 1 M⊙ yr−1) into the central 200 pc where the starburst activity peaks. We suggest that the nuclear gas bar will disappear on timescales ranging from few × 108 years to a Gyr, under the effect of star formation, dynamical friction, and gravitational torque. We also show that NGC 2782 harbors a starburst-driven outflow with a remarkable bubble morphology that has not been observed to date in any other starburst galaxy of comparable luminosity (Jogee et al. 1997a). The outflow is driving hot, warm, and possibly cold phases of the ISM out of the central kpc. The estimated outflow rate is less than the inflow rate, and this suggests the dynamical mass in the inner 100 pc might increase by several folds within a Gyr. These results might be relevant to theory (Shlosman et al. 1989) and simulations (Friedli & Martinet 1993) which propose nuclear bars and ‘bars within bars’ as efficient mechanisms for fueling central starbursts/AGNs.
High Spatial Resolution Near-IR Tip/Tilt Imaging of “Warm” Ultraluminous Infrared Galaxies
Authors: Surace J.A. , Sanders D.B.
Published: July 2016

We present results from high spatial resolution (FWHM ≈ 0.3–0.5″) near-IR (1.6 and 2.1μm) imaging of a complete sample of ultraluminous infrared galaxies (ULIGs) chosen to have “warm” mid-IR colors (f25/f60 > 0.2) characteristic of AGN. In conjunction with our WFPC2 imaging program (Surace et al. 1998), we have found that nearly all of these systems are advanced mergers with complex nuclear morphologies. The extended underlying galaxies are detected in each system at H and K′, and are found to have luminosities of a few L∗, similar to quasars (McLeod & Rieke 1994). Many of the circumnuclear star-forming knots seen at optical wavelengths have been detected. Based on model SEDs, their bolometric luminosities appear similar to those of the extended nuclear starbursts seen in other, less-luminous interacting systems (i.e. NGC 4038/9). Each ULIG is increasingly dominated at long wavelengths by a compact source which we identify as a putative active nucleus. The optical/near-IR colors of these putative nuclei are more extreme than the most infrared-active starburst galaxies, yet are identical to “far-IR loud” quasars which are in turn similar to optical quasars with significant hot (800 K) dust emission. Half of the ULIGs have dereddened nuclear near-IR luminosities comparable to those of QSOs, while the others resemble Seyferts; this may be an effect of patchy extinction and scattering. Similarities between the putative ULIG nuclei and QSO nuclei, the underlying host galaxies, and the apparent young age of the ULIGs (as evidenced by their compact star-forming knots) support the evolution of “warm” ULIGs into optical QSOs.
Compact Groups of Galaxies
Authors: Hickson P.
Published: July 2016

This paper reviews some of the outstanding questions concerning compact groups of galaxies. These relate to the physical nature and dynamical status of the groups, their formation and evolution, and their role in galaxy evolution. The picture that emerges is that compact groups are generally physically dense systems, although often contaminated by optical projections. Their evolution is likely a continuous process of infall, interaction and merging. As new galaxies are added, and previous ones merge, the membership of the group evolves. I suggest that while the size of the group changes little, other physical properties such as total mass, gas mass, velocity dispersion, fraction of early-type galaxies increase with time. This picture is at least qualitatively consistent with observations and provides a natural explanation for the strongest correlations found in compact group samples.
Investigations of Environmental Effects in Clusters of Galaxies Using N-Body Simulations
Authors: Popescu N.A. , Suran M.D.
Published: July 2016

In order to investigate cluster evolutionary effects we present a new chemo-dynamical model. The model takes into account N-body simulations, modified for galaxy-galaxy binary encounters. The model incorporates also the codes for spectrophotometric and chemical evolution of galaxies. In the same time the calculations include the interaction between two merging subclusters.
A New Automated Sample of Compact Groups of Galaxies
Authors: Iovino A. , Tassi E. , de Oliveira C. Mendes , Hickson P. , Macgillivray H.
Published: July 2016

Compact Groups (CGs) of galaxies represent an extreme class of objects. They typically contain 4-8 galaxies with high space density (as in the centers of rich clusters) but with low velocity dispersions, being an excellent laboratory for the study of galaxy interactions and their effects. Up to now no unbiassed sample of CGs was available in the literature, and therefore several of the classical problems and paradoxes involving CGs could not be properly addressed.
The High Redshift Population of Field Galaxies
Authors: Koo David C.
Published: July 2016

In principle, observations of the high redshift population of field galaxies should provide powerful probes of interactions and mergers. As initial examples of such explorations, we highlight recent results from the DEEP program that take advantage of Keck andHST, including median redshifts for samples fainter thanI~ 22, morphologies and colors toz~ 1, and especially the nature ofz~ 3 galaxies in the Hubble Deep Field. Although tantalizing, the results will need much larger samples to be confirmed and better quantified.
Are Pressure-Confined Clouds in Galactic Halos Possible Models of Lyman Alpha Clouds?
Authors: Miyahata Keiko , Ikeuchi Satoru
Published: July 2016

Our understanding of the Lyα forest has changed considerably following observations by HST and Keck. Lyα clouds at low redshifts (z < 1.7) observed by HST showed two unexpected features: Lanzetta et al. (1995) found that most luminous galaxies at such redshifts produce Lyα absorptions at mean impact parameter ~160h−1kpc, and established the association between Lyα clouds and galaxies. Ulmer (1996) pointed out the strong clustering of Lyα clouds in this redshift range. Motivated by the above, we propose a two-component protogalaxy model for the Lyα clouds based upon our previous work (Miyahata & Ikeuchi 1995). In our model, the Lyα clouds are stable cold clouds confined by the pressure of ambient hot gas in a galactic halo. We determine the properties of these cold clouds and hot gas on the basis of theoretical and observational constraints. We take into account the stability of a cold cloud in the galactic halo in addition to the general stability conditions in a two-component medium (e.g. Ikeuchi & Ostriker 1986), and compare the derived quantities of Lyα clouds in the galactic halo and in the intergalactic medium at both high and low redshifts. We conclude that the ciondition that a cloud is stable against both evaporation and tidal disruption by a hot galactic halo is very restrictive. In the most noteworthy example at z ~ 0.5, a pressure-confined, stable spherical Lyα cloud with NHI = 1014cm−2 cannot survive in the galactic halo, although much higher column density clouds of NHI = 1017cm−2 can. Miyahata & Ikeuchi (1997) discuss how these results constrain an alternative model for Lyα clouds associated with the galaxies observed by Lanzetta et al. (1995).
Abundances in the Galactic Disk
Authors: Edvardsson Bengt
Published: July 2016

The empirical study of the build-up of chemical abundances in the galactic disk is an important route to our understanding of the history of the Galaxy. It supplies a wealth of constraints to the models and simulations being done. There are, however, still many unanswered questions concerning the details of the abundance patterns, and many uncertainties and possibly inconsistencies in the data at hand. Ideally one would like to map the abundances of individual elements as a function of time and 3-dimensional position in the disk. The study of the ISM today and of the surfaces of individual stars as probes of the ISM from the time and position of their formation help us in this endeavour.
Age Problem Based on the Abundance Ratio from a High-Redshift QSO
Authors: Tsujimoto T. , Yoshii Y. , Kawara K.
Published: July 2016

The age of a high-redshift QSO can constrain the cosmology by placing a limit on the cosmological time. We use the observed FeII (UV+optical)/MgIIλ2798 flux ratio from the broad-line gas of a QSO at z=3.62 to estimate the abundance ratio [Mg/Fe] and predict that the QSO is at least 1.3 Gyr old from the chemical analysis using the abundance ratio [Mg/Fe] as a cosmic clock. Our result favors a nonzero cosmological constant and thus conflicts with a flat, matter-dominated universe.
Gamma-Ray Line Spectroscopy Results from COMPTEL
Authors: Schönfelder V.
Published: July 2016

Comptel aboard NASA's Compton Observatory has led to a major progress in the field of astronomical gamma-ray line spectroscopy. Highlights are the all-sky map of the 1.8 MeV line from radioactive 26Al, the first detection of the 1.156 MeV line from radioactive 44Ti from a Supernova remnant (Cas A), and the detection of excessive MeV emission from the Orion complex that may be ascribed to excitation of 12C and 16O nuclei.
Non-Equilibrium Condition in the SNR
Authors: Tsunemi H.
Published: July 2016

SNe are one of the major source of the heavy elements in Galaxy. They produced high temperature plasma heavily contaminated with heavy elements mixing with the interstellar matter. Due to the temperature and the density, the shock heated plasma does not reach the collisional ionization condition in young SNR, like Cassiopeia A, Tycho and Kepler. The emission is well represented with a non-equilibrium condition plasma.
Astrophysical Plasmas and Atomic Processes
Authors: Kaastra J.S.
Published: July 2016

Several plasma codes are available for the analysis of hot astrophysical plasmas. Among the oldest are the Raymond-Smith model (Raymond & Smith 1977) and Mewe-Gronenschild model (Mewe et al. 1985, 1986). Minor updates to this last code have resulted in the meka model (Kaastra 1992); major updates (most importantly the ionization balance and the treatment of the Fe-L complex) resulted in the mekal code (Mewe, Kaastra & Liedahl 1995). Here also the plasma codes of Masai (1984) and Landini & Monsignori Fossi (1990) should be mentioned. The RS, meka and mekal codes are included in the XSPEC fitting package, the latest mekal code is incorporated in the SPEX package (Kaastra et al. 1996). Both Masai's code and SPEX contain non-equilibrium ionization (NEI) modes. All these codes differ in details, see Brickhouse et al. (1995) for an overview. Most important for the analysis of X-ray data is the ionization balance that is used for iron and the treatment of the Fe-L complex.
Hot Plasma in the Galaxy
Authors: Yamauchi S.
Published: July 2016

In the X-ray band, we can see weak and extended X-rays along the Galactic plane and near the Galactic Bulge region, although these regions are dominated by many point sources (e.g., Warwick et al. 1985). The Tenma satellite discovered conspicuous emission lines from selected regions near the Galactic plane (Koyama et al. 1986). These lines are identified with K-shell line from He-like Fe, hence the extended emission is attributable to optically thin hot plasmas with temperatures of several keV. The origin of the thin hot plasmas, however, have been debatable, because no class of X-ray objects shows such high temperature plasma emissions. To investigate the origin of the extended X-rays, we are currently observing the Galactic plane regions with the ASCA satellite. In this paper, we report on the ASCA results: the hard X-ray imaging and spectroscopy of the hot plasma in the Galaxy.
Metal Abundances in the Hot ISM of Elliptical Galaxies
Authors: Loewenstein M. , Mushotzky R. F.
Published: July 2016

In elliptical galaxies, where most of the stars were formed at an early epoch, the total mass, spatial distribution, and relative abundances of metals are intimately connected to the galaxy formation process. Determinations of the hot interstellar medium metallicity from X-ray spectral analysis are more direct, less model-dependent, and more radially extensive than optical estimates based on broad-band colors or line indices, and provide a view into the nucleosynthetic histories of elliptical galaxies.