bluuebunny/crossref_metadata_2025 huggingface dataset:
7.11. Inside the central cavity
Authors: Mezger Peter G. , Philipp Sabine
Published: July 2016

The Circum-Nuclear Disk (CND) is probably a by-product of the explosive event which created Sgr A East. Its inner edge of radius R ~ 1.7pc is well developed and comprises the Central Cavity (CC) which is filled with ~ 260 M⊙ of ionized gas. ISM appears to flow through the CND into the Central Cavity at a rate of M ~ 0.01 M⊙yr−1. Dust and Lyman continuum luminosities of the central 1.25 parsec, corrected for photons not absorbed by dust and gas inside the CC are ~ 108L⊙ and ~ 1051 Lyc photons s−1, most of which are provided by a cluster of 24 hot and massive stars, which also provide ~ 1/3 of the integrated K-band flux density (see the recent review by Mezger et al., 1996). A larger number of cool M- and K-giants and more than a million low-mass MS stars provide the remaining flux density, which comes from a diffuse background emission first seen in our NIR mosaic maps (Zylka et al., 1997).
7.16. A possibility of direct determination of the star phase density in the Galactic nuclear cluster
Authors: Fridman A.M. , Polyachenko E.V. , Polyachenko V.L.
Published: July 2016

Line-of-sight and proper motions data for stars near the Galactic center have evolved in recent years (see, e.g. Eckart & Genzel). The data were used for determining the star velocity dispersions in different directions (with a result that the velocity distribution is isotropic to within the observational error). Here we note that there exists a possibility for determining the star phase density itself from such data. The method is based on the solution of the corrensponding integral equations with their left sides being calculated from radial velocities and proper motions. Remind that discussion of the problems connected with reconstruction of the phase density from the radial velocity data was started by Merritt. There is some difference in applying this approach to self-gravitating systems (open and globular clusters) and clusters within external gravitational field. Among the latter is, for example, the inner parts of the Galactic nuclear cluster: they are governed by the field of the central black hole. It follows from the proper motions data estimates for a mass within a radius of 0.16 pc and within 0.083 pc given by Eckart & Genzel (cited above). In the case of the cluster in the field of the black hole we have no need of information about the densities σ(s) (s is the projected radius) and ρ(r) (since the method uses only the gravitational potential Φ(r), which here is foregone: Φ(r) = −GMh/r). Unfortunately, the data on the stars around the central black hole are yet inadequate to derive the distribution function with satisfactory accuracy. (Obviously the necessary data will be available before long.) So we restrict ourselves to only testing the computer algorithms used on the example of the simplest (Plummer) model, for which f(E) ∞ (–E)7/2.
8.2. Magnetic fields and black holes in galactic nuclei
Authors: Blandford R. D.
Published: July 2016

Recent observations have strengthened the dynamical arguments for the presence of black holes in X-ray binary systems, the Galactic center and the nuclei of the majority of bright galaxies. They have also drawn attention to the fact that accretion does not always proceed in the simple, stationary manner envisaged in early theories. I wish to discuss four related topics that are relevant to understanding the behavior of accreting black holes. (In view of the length constraints imposed by conference proceedings I shall make no attempt to give adequate bibliographic references for what follows.)
8.10. Three-dimensional global MHD simulations of jet formation in active galactic nuclei
Authors: Matsumoto R. , Shibata K.
Published: July 2016

Magnetically driven jets from accretion disks are considered to be the most promising models of astrophysical jets. Uchida & Shibata (1985) and Shibata & Uchida (1986) first carried out two-dimensional nonlinear MHD simulations of jet formation from a magnetized disk. Matsumoto et al. (1996) applied the Uchida-Shibata model to a gas torus in active galactic nuclei and showed that the surface layer of the torus accretes faster than the equatorial region like an avalanche because magnetic braking most effectively extracts angular momentum from that layer. A magnetized torus subjects to global non-axisymmetric instabilities (Curry & Pudritz 1996) and local magnetorotational instability (Balbus & Hawley 1991). We carried out three-dimensional global MHD simulations to show the non-axisymmetric effects on the torus, avalanche flow and jet formation.
9.3. A massive BH in the edge-on E/S0 galaxy NGC 4342
Authors: van den Bosch Frank C. , Cretton Nicolas
Published: July 2016

We present evidence that the edge-on E/S0 galaxy NGC 4342 harbours a massive BH of ~ 3.0 × 108M⊙. The evidence is based on a comparison of fully general three-integral models with both ground-based and HST/FOS kinematics.
9.4. Nuclear gas kinematics of NGC 7052 and IC 1459 from HST/FOS spectra
Authors: van der Marel Roeland P.
Published: July 2016

We have obtained HST/FOS measurements of the nuclear kinematics of the gas disks in NGC 7052 and IC 1459. The spectra show steeper rotation curves and broader emission lines than ground-based data. Detailed modeling is in progress to constrain the mass of possible black holes.
9.6. Dynamical models of NGC 3115
Authors: Emsellem E. , Dejonghe H.
Published: July 2016

We present here axisymmetric two and three integral models of the S0 galaxy NGC 3115. The light and mass models are based on an application of the Multi-Gaussian Expansion (MGE) method on V band images of NGC 3115. The resulting model fits the photometry from the central HST pixel (0.045 arcsec) up to a radius of ~ 500 arcsec (combining a wide field image kindly provided by Cecilia Scorza, an HRCAM/CFHT image, and the WFPC2/HST image). The deprojection is analytical if each component corresponds to a 3D Gaussian. Here, the model is assumed axisymmetric. The analytical expression of the luminosity density serves as the input for all the dynamical models.
9.7. High-resolution 22 GHz continuum observations of NGC 4258
Authors: Herrnstein J.R.
Published: July 2016

VLBA observations of the water megamaser in NGC 4258 reveal an extremely thin, nearly edge-on, slightly warped disk in Keplerian rotation around a 3.5 ± 0.1 × 107M⊙ central mass (Miyoshi et al. 1995). The masers extend from 0.13-0.26 pc (assuming a distance of 6.4 Mpc), and provide an unusual opportunity to probe active galactic nuclei (AGN) accretion on sub-parsec scales and in a system where the mass of the central engine and the geometry of the outer accretion disk are known with precision. Here, I discuss new 22 GHz, VLBA continuum observations of NGC 4258 in the context of advection-dominated accretion models. A more detailed discussion is in preparation (Herrnstein et al. 1998).
9.14. A simple mass estimate for central black holes in cuspy galaxies
Authors: de Rijcke S. , de Bruyne V. , Dejonghe H. , Mathieu A.
Published: July 2016

We argue that the velocity dispersion of the stars is likely a monotonically decreasing function of radius along the minor axis in the central regions of cuspy galaxies. We show that then a central mass concentration (a black hole) must be present and calculate its minimum mass, M⊙. This lower bound is relevant and entirely consistent with current mass estimates.
10.1. The nuclear star cluster of the Milky Way: star formation and central dark mass
Authors: Genzel R. , Eckart A.
Published: July 2016

High spatial resolution, near-infrared imaging and spectroscopy of the nuclear star cluster obtained in the last few years have given key new insights about the structure, evolution and mass distribution in the Milky Way Center. The central parsec is powered by a cluster of hot, massive stars. Their characteristics imply that there was an active phase of star formation a few million years ago, probably triggered by the infall and collapse of a very dense gas cloud. Other such starburst episodes may have taken place between 100 and 300 million years ago. Measurements of radial and proper motions for more than 200 stars show that stellar velocities increase with a Kepler law down to a scale of a light week from the compact radio source Sgr A∗. The data make a compelling case for the presence of a compact, central dark mass of about 2.6×106 M⊙. Simple physical considerations show that this dark mass cannot consist of a stable cluster of stars, stellar remnants or substellar condensations. Energy equipartition requires that at least five percent of the dark mass (≥105 M⊙) must be associated with Sgr A∗ itself and likely is enclosed within less than 8 light minutes. If one accepts these arguments it is hard to escape the conclusion that Sgr A∗ is indeed a massive black hole at the core of the Milky Way.
10.5. Short-term variability of Sagittarius A∗ at millimeter wavelengths
Authors: Tsutsumi T. , Kawabata T. , Miyazaki A. , Tsuboi M.
Published: July 2016

Time variability of Sgr A∗ at cm wavelengths is well known phenomenon and has been studied by several authors (e.g. Lo 1989; Zhao et al. 1992). On the other hand, variability at millimeter wavelengths is not well established. Wright & Backer (1993) reported significant flux variations at λ = 3.4mm in a month during the decay of a flare observed by the Very Large Array in 1990. However others found no variability at millimeter and submillimeter wavelengths (Gwinn et al. 1991; Zylka et al. 1995). Emission from extended component surrounding Sgr A∗ is significant even at millimeter wavelengths (e.g. Tsuboi et al. 1988), thus it is important to observe with a narrower beam to isolate the compact component for accurate measurement of variability of Sgr A∗. Here we present some results from an on-going millimeter monitoring program of Sgr A∗ with the Nobeyama Millimeter Array (NMA).
11.8. High collimation of electron-positron pair jets proceeding to radio jets
Authors: Kondo M.
Published: July 2016

The one of the possibilities concerning the cause of AGN jets is the super-Eddington luminocity around the Massive Black Hole. If the case of optically thick state is assumed, we can define the super-Eddington temperature in the optically thick case, from the following condition that
where r∗ = 2c2r/GM. The creation of electron- positron pairs and the pahse change are expected to occur in the such temperature rage around 109K, where the radiation pressure is dominant in the lower temperature and the pair pressure be in the higher one.
11.11. OJ 287 – a system with a binary black hole
Authors: Lehto Harry J.
Published: July 2016

OJ 287 is a blazar type active galaxy. The historical light curve shows outbursts occurring at quasi-regular intervals. These can be modeled by a secondary black hole interacting with the accretion disk of the primary black hole. We present results of wavelet analysis of the recent light curve of OJ 287, including the outbursts in 1994 and 1995.
11.12. X-ray emission from LINERs observed with ASCA
Authors: Terashima Y. , Kunieda H. , Serlemitsos P.J. , Ptak A.
Published: July 2016

We present X-ray observations of LINERs with ASCA. We detected a hard point-like source of X-ray luminosity of 1040–1041 erg s−1 at the nucleus. Their hard X-ray continuum is well represented by power-law of photon index ~ 1.8. The X-ray to Hα luminosity ratio LX/LHα is quite similar to Seyfert galaxies and strongly support the presence of low luminosity AGNs.
11.13. Gravitational waves generated by globular cluster systems collapse
Authors: Capuzzo-Dolcetta R. , Miocchi P.
Published: July 2016

The hypothesis -raised and discussed in - that the source of AGN fueling can be, at least in elliptical galaxies, stars belonging to a dense stellar environment formed by globular clusters frictionally decayed and tidally destroyed by the gravitational field of central black hole (b.h.), is strongly supported in. The quantity of star mass swallowed by the b.h. and its time rate seem at all compatible with those needed to justify the intensity and time characteristics of galactic nuclei activity (see also).
Of Cosmic Background Anisotropies
Authors: Smoot G.F.
Published: July 2016

Observations of the Cosmic Microwave Background (CMB) Radiation have put the standard model of cosmology, the Big Bang, on firm footing and provide tests of various ideas of large scale structure formation. CMB observations now let us test the role of gravity and General Relativity in cosmology including the geometry, topology, and dynamics of the Universe. Foreground galactic emissions, dust thermal emission and emission from energetic electrons, provide a serious limit to observations. Nevertheless, observations may determine if the evolution of the Universe can be understood from fundamental physical principles.
Radio Galaxies and Quasars as Cosmological Probes
Authors: Singal Ashok K.
Published: July 2016

Various techniques and methods that have been developed for using extragalactic radio sources as cosmological probes of the universe are listed. The discussion is mainly confined to the cosmological tests employing extended radio sizes of powerful radio galaxies and quasars as standard metric rods (in a statistical sense) to figure out the geometry of the universe. Some comments are made on the recent use of the milliarcsec scale sizes of compact radio sources for angular size–redshift tests. It is further pointed out that the estimates of clustering for quasars selected at centimetre wavelengths could be seriously affected by the relativistic beaming.
High Redshift Radio Galaxies
Authors: Dunlop James S.
Published: July 2016

The potentially important role of jet-cloud interactions in determining the appearance of high-redshift radio galaxies is discussed and investigated via new 3-dimensional simulations of off-axis jet-cloud collisions. The results indicate that the most powerful radio sources are likely to be observed during or shortly after a jet-cloud interaction, and that such interactions can explain both the radio structures and the spatial association between optical and radio light found in powerful radio galaxies at high redshift. It is argued that, due to the radio-power dependence of such complicating effects, the optical-infrared colours and morphologies of very radio-luminous high-redshift galaxies can tell us essentially nothing about their evolutionary state. Either one must study much less radio-luminous sources in which the AGN-induced contamination is minimised, or one must attempt to determine what fraction of the baryonic mass of the radio galaxy has been converted into stars at the epoch of observation. Recent observations aimed at performing the latter experiment on two well-known high-redshift radio galaxies (4C 41.17 & B2 0902+34) are described. It is concluded that at present there exists no clear evidence that either of these famous galaxies is ‘primæval’; on the contrary, the continued low-dispersion of the infrared Hubble diagram atz> 2 points toward a much higher redshift of formation for elliptical galaxies.
A Search for Gravitational Milli–Lenses
Authors: Wilkinson P.N. , Henstock D.R. , Browne I.W.A. , Readhead A.C.S. , Taylor G.B. , Vermeulen R.C. , Pearson T.J. , Xu W.
Published: July 2016

We have searched for gravitational milli–lens systems by examining VLBI maps of ~ 300 flat–spectrum radio sources. So far we have followed up 7 candidates, with separations in the range 2–20 mas. None have been confirmed as lenses but several of them can not yet be definitively ruled out. If there are no milli-lenses in this sample then uniformly–distributed black holes of 106to 108M⊙cannot contribute more than ~ 1% of the closure density.
The COBE DIRBE Search for the Cosmic Infrared Background
Authors: Hauser Michael G.
Published: July 2016

The Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer (COBE) satellite is designed to conduct a sensitive search for isotropic cosmic infrared background radiation over the spectral range from 1.25 to 240 μm. The cumulative emissions of pregalactic, protogalactic, and evolving galactic systems are expected to be recorded in this background. The DIRBE instrument has mapped the full sky with high redundancy at solar elongation angles ranging from 64°to 124°to facilitate separation of interplanetary, Galactic, and extragalactic sources of emission. Conservative limits on the isotropic infrared background are given by the minimum observed sky brightnesses in each DIRBE spectral band during the 10 months of cryogenic operation. Extensive modeling of the foregrounds is under way to isolate or strongly limit the extragalactic infrared component. The current approach to these modeling efforts is described and representative present residuals are reported.
Faint Field Galaxy Counts, Colors, and Redshifts
Authors: Koo David C.
Published: July 2016

This paper aims to provide the non-specialist a brief overview and major highlights in the rapidly changing research area of faint field galaxy evolution. Special emphasis is given to number counts, colors, and redshifts more recent than 1992 and their interpretation, both conventional and exotic. We close with previews of new directions that exploit sizes and velocity widths to explore the nature of faint blue galaxies, a puzzle that has defied solution for 15 years. The mystery continues.
The HST Medium Deep Survey: Galaxy Morphology at High Redshift
Authors: Griffiths R. E. , Ratnatunga K. U. , Casertano S. , Im M. , Neuschaefer L. W. , Ellis R. S. , Gilmore G. F. , Elson R. A. W. , Glazebrook K. , Santiago B. , Windhorst R. A. , Driver S. P. , Ostrander E. J. , Mutz S. B. , Koo D. C. , Illingworth G. D. , Forbes D. A. , Phillips A. C. , Green R. F. , Huchra J. P. , Tyson A. J.
Published: July 2016

With HST and WFPC2, galaxies in the Medium Deep Survey can be reliably classified to magnitudesI814≲ 22.0 in the F814W band, at a mean redshift. The main result is the relatively high proportion (~40%) of objects which are in some way irregular or anomalous, and which are of relevance in understanding the origin of the familiar excess population of faint galaxies. These diverse objects include compact galaxies, apparently interacting pairs, galaxies with superluminous starforming regions and diffuse low surface brightness galaxies of various forms. The ‘irregulars’ and ‘peculiar’ galaxies contribute most of the excess counts in the I-band at our limiting magnitude, and may explain the ‘faint blue galaxy’ problem.
The Far-Ultraviolet Background
Authors: Jakobsen Peter
Published: July 2016

Extensive reviews of the diffuse background at ultraviolet (λ1000 – 2500 å) wavelengths have been given by Davidsen, Bowyer & Lampton (1974), Paresce & Jakobsen (1980), and most recently by Bowyer (1992) and Henry (1992). Since many astronomical sources emit radiation with photon energies in the rangehv≃ 10 – 20 eV through various thermal and non-thermal emission processes, the diffuse UV background is of relevance for a range of topics. These include the study of the properties of interplanetary and interstellar dust grains, thermal line emission from the interstellar and intergalactic gas, the integrated light of galaxies, and radiative decay of exotic cosmological particles.
Evolution of the EUV Background from Quasar Absorption Line Studies
Authors: Bechtold Jill
Published: July 2016

The integrated extreme ultraviolet (EUV) radiation from quasars and other high redshift sources provides an ambient ionizing radiation field which may photoionize the gas seen as quasar absorption lines. In particular, the observed evolution of the Lyα forest clouds probably results in part from the evolution of the EUV metagalactic field. Estimates of the EUV field as a function of redshift can be made from measuring the “proximity effect” in quasar spectra; uncertainties in these estimates may be large. Given the uncertainties, the estimated EUV field at z≈3 derived from the proximity effect is in reasonable agreement with the expected contribution from luminous quasars.
Big Bang Scenario and Nature of Dark Matter
Authors: Novikov I.
Published: July 2016

We give a brief review of a problem of dark matter in the Universe. The key questions regarding dark matter are discussed: what is the distribution of dark matter at different scales? What is the nature of dark matter? Is there baryonic dark matter? We discuss a few new techniques of the investigation of dark matter in the Universe. We discuss the peculiar periodic dependence of the initial spectrum of the baryonic matter distribution on wavelength at the moment of recombination (Sakharov oscillations). Sakharov oscillations should manifest themselves by the specific anomalies in the angular correlation function of the microwave background anisotropy on scales 10′ – 2°, practically in any cosmological model. We discuss special methods for filtering of this effect in the observational data.
Inflation, Microwave Background Anisotropy, and Open Universe Models
Authors: Frieman J.A.
Published: July 2016

The inflationary scenario for the very early universe has proven very attractive, because it can simultaneously solve a number of cosmological puzzles, such as the homogeneity of the Universe on scales exceeding the particle horizon at early times, the flatness or entropy problem, and the origin of density fluctuations for large-scale structure [1]. In this scenario, the observed Universe (roughly, the present Hubble volume) represents part of a homogeneous inflated region embedded in an inhomogeneous space-time. On scales beyond the size of this homogeneous patch, the initially inhomogeneous distribution of energy-momentum that existed prior to inflation is preserved, the scale of the inhomogeneities merely being stretched by the expansion.
X-Ray Observations of Galaxy-Quasar Associations
Authors: Arp H.
Published: July 2016

Five examples of close associations of quasars with bright, low redshift galaxies have been observed in X-ray wavelengths with ROSAT. In three cases where the galaxies are detected strongly, the nuclei of the galaxies have X-ray extensions in the direction of the adjacent quasars.

In all cases the active galaxies and quasars are located at the origin of apparent lines or pairs of X-ray sources, some involving filamentary X-ray connections to fainter quasars or candidate blue stellar objects. Brighter X-ray sources in these fields are found to be in excess of average survey values. The filaments and connections have measured fluxes of 1 ≲FX≲60 × 10−13erg cm−2s−1and they tend to radiate more strongly in the harder end of the 0.1-2.4 keV energy band.

The most surprising result is the evidence that X-ray sources of optically diverse character are linked together in lines and extended filaments. Because of the rapid decay time of the high energy X-ray radiation, it is implied that we are observing some ongoing process possibly related to matter creation or emergence.
Background Radiation: Probes and Future Tests
Authors: Rees Martin J.
Published: July 2016

The clearest evidence for the ‘hot big bang’ is of course the microwave background radiation. Its spectrum is now known, from the FIRAS experiment on COBE, to be a very precise black body – indeed, the deviations due to high-z activity, hot intergalactic gas, etc are smaller than many people might have expected. Also the light element abundances have remained concordant with the predictions of big bang nucleosynthesis, thereby giving us confidence in extrapolating back to when the universe was a few seconds old (see Copi, Schramm and Turner 1994 for a recent review). These developments give us grounds for greater confidence in this model than would have been warranted ten years ago. Several things could have happened which would have refuted the picture, but they haven't happened. For instance:

(i)

Objects could have been found where the helium abundance was far below 23 per cent.

(ii)

The background spectrum at millimetre wavelengths could have been weaker than a black body with temperature chosen to fit the Rayleigh-Jeans part of the spectrum.

(iii)

A stable neutrino might have been discovered in the mass range 100eV-1MeV.
Panel Contribution–IAU Symposium 168
Authors: Partridge R.B.
Published: July 2016

These brief comments will reflect the point of view of an observer, rather than a theorist. They will also be quite informal, as were the remarks I made while at the symposium in The Hague. Finally, I will restrict myself to relatively low energy proton backgrounds-roughly speaking from 10−5–101eV. I fear that will slight the important work being done by our colleagues on the X-ray and gamma ray backgrounds, but those topics were nicely covered in the symposium itself.
CMB: Anisotropies Due to Non-Linear Clustering
Authors: Martínez-González E. , Sanz J. L.
Published: July 2016

Most of the studies on the anisotropy expected in the temperature of the cosmic microwave background (CMB) have been based on linear density perturbations. The anisotropies at angular scales ≥ 1o(horizon at recombination) are preserved during the evolution of the universe, whereas for smaller scales new effects can appear, generated during the non-linear phase of matter clustering evolution: i) the Sunyaev-Zeldovich effect due to hot gas in clusters (Scaramella et al. 1993), ii) the Vishniac effect (Vishniac 1987) due to the coupling between density fluctuations and bulk motions of gas and iii) the integrated gravitational effect (Martínez–González et al. 1994) due to time-varyng gravitational potentials. A single potential φ(t, x), satisfying the Poisson equation, is enouph to describe weak gravitational fields associated to non-linear density fluctuations when one considers scales smaller than the horizon and non-relativistic peculiar velocities. The temperature anisotropies, in a flat universe, are given by the expression (Martínez–González et al. 1990)
New Results on CMB Structure from the Tenerife Experiments
Authors: Davies R.D. , Gutiérrez C.M. , Watson R.A. , Rebolo R. , Lasenby A.N. , Hancock S.
Published: July 2016

Temperature fluctuations in the CMB (Cosmic Microwave Background) are a key prediction of cosmological models of structure formation in the early Universe. Observations at the Teide Observatory, Tenerife using radiometers operating at 10, 15 and 33 GHz have revealed individual hot and cold features in the microwave sky at high Galactic latitudes. These well-defined features are not atmospheric or Galactic in origin; they represent the first detection of individual primordial fluctuations in the CMB. Their intensity is defined by an intrinsicrmsamplitude of 54−10+14μK for a model with a coherence angle of 4°. The expected quadrupole term for a Harrison-Zel'dovich spectrum isQRMS–PS= 26 ± 6 μK. When our data at Dec=+40° are compared with the COBE DMR two-year data, the presence of individual features is confirmed. New experiments to detect structure on smaller scales are described.
On the Use of Fractal Concepts in Analysis of Distributions of Galaxies
Authors: Vavilova I.B.
Published: July 2016

The well- grounded polemics about the fractal structure of the Universe and a new cosmological picture which appears in connection with this, in first instance the absence of any evidence for homogenization up to present observational limits 200h−1Mpc, have been detailed at the work by Coleman, Pietronero (1992). Two versions on nature of fractal pattern of the galaxy distribution in the observed universe also are now: it behaves like a simple homogeneous fractal (Pietronero 1987; Coleman et al. 1988) and as a multifractal - fractal having more than one scaling index (Jones et al. 1988; Martinez, Jones 1990; Martinez et al. 1990; Borgani et al. 1993 (with the good review for matter of above)).

This work does not play decisively into hands of these versions so the fractal concepts, exactly a selfsimilarity and multifractal, were applied here for the analysis oftwo - dimensionaldistribution of thebrightgalaxies and dwarf galaxies of the low surface brightness (LSBD) belonging to the Local Supercluster (LS). But if the observed universe holds the fractal structure, so it is useful to trace over the lower fractal pattern on the small scales of clustering of galaxies within the framework of the known superclusters and, in the first instance, within the local overdensity of galaxies. This work is a preliminary before preparing one with the same analysis of three- dimensional distribution of galaxies of LS.
Milliarcsecond Radio Structure of AGN as a Cosmological Probe
Authors: Gurvits L.I.
Published: July 2016

Recent achievements in Very Long Baseline Interferometry (VLBI) allow the reconsideration of milliarcsecond radio structure of Active Galactic Nuclei (AGN) as a “standard object”. The basic concept of this approach is described and illustrated.
Vacuum-Energy and the Angular-Size/Redshift Diagram for Milliarcsecond Radio Sources
Authors: Jackson J. C. , Dodgson Marina
Published: July 2016

We have considered two compilations of angular-size/redshift data for ultra-compact radio sources, due to Kellerman (1993) and Gurvits (1994) respectively, and a family of homogeneous isotropic universes with two degrees of freedom, represented by pressure-free matter and vacuum-energy. Kellerman's results seem to support the canonical modelq0= 1/2, ω0= 1; the question posed here is: can we produce significant deceleration without dark matter?
Intermediate Resolution Spectroscopy of the Radio Galaxy B2 0902+34 at Z ≈ 3.4
Authors: Sanz J. L. , Martín-Mirones J. M. , Martínez-González E. , González-Serrano J. I.
Published: July 2016

We have carried out optical spectroscopic observations at intermediate spectral resolution of the massive high redshift radio galaxy 0902+34 atz≈ 3.39. This source was first identified by Lilly (1988) (from hereafter L88). The study of high redshift radio galaxies is interesting to analyze the physical conditions of the early universe and the galaxy evolution at cosmological redshifts. It has been claimed that some of these systems may be protogalaxies in the process of formation. Indications for this are the flat spectrum and the absence of the 4000 Å break, features which have already been observed in many cases. In particular, observations in the spectral range fromVtoKsuggest that 0902+34 is a young galaxy (Eisenhardt and Dickinson 1992). Recent radio observations of the 21 cm line of neutral hydrogen have detected (Uson et al. 1991) an absorption against the radio continuum source. This absorption could also leave a track in the optical, redwards the Lyα line. Our observations were carried out with the ISIS spectrograph at the 4.2 m William Herschel Telescope (seeing ≈ 1.2–1.6 arcsec). A spectral dispersion of 0.78 Å/pixel (blue arm) and 1.38 Å/pixel (red arm) was obtained. Å long slit of width 3′ was used providing a spectral resolution of ≈ 5.4 Å in the blue arm and of ≈ 9.5 Å in the red one. Both resolutions are a clear improvement over that achieved by L88 of 20 Å, allowing us to resolve the Lyα line (and its possible structure) and any other possible strong features appearing in the spectral range observed (e. g., C iv λ1549, He ii λ1640, …). Six different observations of 2700 s of the radio galaxy 0902+34 were carried out. The slit was rotated to coincide with the parallactic angle at the beginning of each exposure. This will allow us to map spectroscopically different regions of the galaxy (for more details see Martín-Mirones et al. 1994).
Evolution of Galaxy Luminosity in the CDM Model
Authors: Mosconi Mirta , Tissera Patricia , Lambas Diego Garcia
Published: July 2016

we analyze the evolution of the luminosity function of galaxies using the CDM model in numerical simulations. There is an observational excess in the number counts of galaxies per square degree in the blur band Nb(i.e. APM, Maddoxet al.1990). Several authors have tried to reproduce it trying to fit the observations. Our model assumes an instantaneous star formation rate (SFR) proportional to a power of the local density. A ‘single star burst’ is produced each time step and we follow the evolution of the luminosity and colour of each ‘stellar group’. The galaxies are identified with a density criterium. We compute U,V,B,K colours and Nband our results agree quite well with observations.
Cosmological Parameters Determinations from Deep Sky Red Shift Surveys
Authors: Suran Doru Marian
Published: July 2016

A new cosmological method and new calculations are presented in order to derive the cosmological fundamental parameters (H0, ω0, δ0) using theobserved correlation function.
A Statistical Study of Enviroment Effects on Galaxy Properties
Authors: Valotto Carlos A. , Lambas Diego Garcia
Published: July 2016

We perform statistical analyses in the CfA and SRC 2 catalogs regarding the dependences of galaxy morphology and galaxy circular velocity on enviroment.
Superclusters and Supervoids
Authors: Kuneva I. , Kalinkov M.
Published: July 2016

A new catalog of superclusters from the entire sky cluster catalog of Abellet al.(1989) is compiled. In fact the last version ofReference Catalog of ACO Clusters of Galaxies(Kalinkov and Kuneva 1994) is used. The RC contains information of optical, radio and X-ray observations gathered from catalogs, lists and papers.
The Time Delay Between QSO 0957+561 A, B
Authors: Pelt J. , Kayser R. , Schild R. , Thomson D.J.
Published: July 2016

We here present a short report about the application of a simple time delay estimator to the extensive data set compiled and partly observed by R. Schild, containing 707 A and B observations with corresponding error estimates from JD 244194 to JD 249169.
Arcs in X-Ray Selected Clusters
Authors: Gioia I.M. , Luppino G.A. , Annis J. , Hammer F. , Lefegvre O.
Published: July 2016

We present the results of an imaging survey to search for gravitationally lensed arcs in a sample of 40 EMSS clusters of galaxies. The lensing frequency obtained suggests that the X-ray selection is the preferred method for finding true, massive clusters which are more likely to exhibit the lensing phenomenon.
Inflationary Cosmogony, Copernican Relevelling and Extended Reality
Authors: Ne'eman Yuval
Published: July 2016

“Eternal” Inflation has relevelled the creation of universes, making it a “routine” physical occurence. The mechanism of the Big Bang, from the conditions triggering it, to the eventual creation of the entire matter content of the resulting universe, involves no singular physical processes. However, causal horizons, due to General Relativity, separate the newborn universe from the parent universe in which it was seeded as a localized vacuum energy. The new universe's expansion only occurs “after” infinite time, i.e. “never”, in the parents frame. This forces a reassessment of “reality”. The two universes are connected by the world line of the initial localized vacuum energy, originating in the parent universe. Assuming that the parent universe itself was generated in a similar fashion, etc., an infinite sequence of previous universes is thus connected by one world-line, like a string of beads.
The New Era in Helioseismology
Authors: Gough D. O.
Published: July 2016

The end of the millennium marks the beginning of the third phase of helioseismology. The first phase was the establishment of the initial astronomical inferences, such as estimates of the depth of the solar convection zone and the protosolar helium abundance, obtained by comparing the seismic properties of theoretical solar models with the first wave of helioseismic data acquired using instruments that had not been designed for the purpose. The second phase was the determination of the spherically symmetric component of the hydrostatic stratification throughout most of the solar interior, and the angular velocity, using inverse methods to analyse the frequencies of normal modes estimated from data obtained most recently from purpose-built networks of ground-based observatories and from space. We have reached the point beyond which further pursuit of the now-well-tried methods to improve the inferences will be apparently slow. The next era will be characterized by painstaking attention to detail, to extract a new level of precision necessary to isolate subtle properties of the sun for asking more sophisticated questions. We are already seeing the normal-mode representation of helioseismic waves being complemented by other representations that may be more suitable for investigating inhomogeneity and time variability particularly of the sun's surface layers. The outcome will enable us to address more accurately issues concerning global dynamics, the equation of state and the chemical composition, and also the properties of convection and the seat of solar activity.
Solar Model with Metal-enhanced Convective Envelope
Authors: Yang J. Y. , Li Y. , Xu H. Y.
Published: July 2016

Solar model with moderate enrichment of heavy elements in the convective envelope is investigated using the up-to-date input physics. It is found that metal enriched model can result in adequate depth of the convection zone and appropriate surface helium abundance, and the agreement between the calculated and observed p-mode frequencies are also improved. The sound speed of our model is worse than SSM and DSM in deep interior, but is better in the base of convection zone.
Variations of the Solar Spectral Irradiance
Authors: Solanki S. K. , Fligge M. , Unruh Y. C.
Published: July 2016

The relative variation of the solar irradiance depends strongly on the wavelength band, with the shortest wavelengths exhibiting the largest variations over the solar cycle. This means that not only the total irradiance varies with solar activity but also the shape of the solar spectrum. These measured effects have been successfully modelled. The models indicate that more than 90% of the total and spectral irradiance variations over the solar cycle are due to the magnetic field at the solar surface. The solar spectral irradiance variations play an important part in constraining the models, since they can directly distinguish between changes in the solar effective temperature and changes produced by variations of solar surface magnetic flux. They also help to determine what fraction of the total solar radiative input to Earth is absorbed by the Earth's atmosphere.
Stellar Irradiance Variations
Authors: Radick R. R.
Published: July 2016

The variability of several dozen stars similar to the Sun in mass, age, and average activity has been monitored regularly in chromospheric Ca II HK emission for over three decades, and photometrically for over fifteen years. Larger samples have been observed less comprehensively. Analogous solar time series exist. A comparison of solar variability with its stellar analogs indicates that the Sun's current behavior is not unusual among sunlike stars. Both solar models and stellar measurements suggest that a true luminosity variation underlies the cyclic total irradiance changes observed on the Sun.
Structure of Procyon A by a seismological approach
Authors: Di Mauro M. P. , Christensen-Dalsgaard J.
Published: July 2016

We consider the theoretical prediction of the power spectrum of oscillations of Procyon A, a bright subgiant star which shows solar like pulsations, comparing models computed by taking into account overshoot from the convective core, as well as diffusion of helium and heavy elements.
An Estimation of Global p-mode Frequencies and Splittings from the IRIS Network Data: 1989–1996
Authors: Ehgamberdiev Sh. A. , Serebryanskiy A. V. , Khalikov Sh. S. , Fossat E. , Gelly B. ,   the IRIS teem
Published: July 2016

The IRIS network has accumulated low-l p-modes data since July, 1989, i.e. one complete solar cycle. Since the last publication of a frequency table (Gelly et al. 1997) the IRIS data bank was not only filled with new data, but also has been supplemented with data from other helioseismology instruments, through cooperative programs. The results of a new estimations of frequencies and splitting obtained from IRIS++ data (Gelly et al. 1998) for period 1989-1996, as well as their variation along the solar magnetic activity cycle are presented.
VIRGO Radiometry and Total Solar Irradiance 1996–2000 Revised
Authors: Fröhlich C. , Finsterle W.
Published: July 2016

The long-term changes of the VIRGO radiometers have been re-analyzed in detail in order to resolve the puzzle of the early increase of the total solar irradiance (TSI) as observed by VIRGO. The exposure dependent changes can be described by a model which is based on a combination of an early increase of the sensitivity and a degradation with time which is modulated by the dose of solar UV radiation each detector receives. After correcting for the exposure-dependent behaviour both operational radiometers show an increase of their sensitivity which depends only on the time they are switched-on. After removing this increase the VIRGO TSI remains more or less constant during the minimum period of solar activity and reaches the solar maximum at levels comparable to the ones of former maxima.
Towards a Generalization of a Mixing-length Model for Nonradially Pulsating Stars: Convection in a Shear
Authors: Houdek G. , Gough D. O.
Published: July 2016

We discuss a generalization of a mixing-length formalism for convection in the presence of a mean flow, and present the convective fluxes for convective cells with the geometry of rolls and of hexagons.
Search for p-mode Frequencies on Procyon A
Authors: Martic M. , Lebrun J. C. , Schmitt J. , Bertaux J.-L.
Published: July 2016

Following the recent evidence for the presence of an excess of power around 1 mHz in the frequency spectrum of the Doppler shift measurements for Procyon (Martic et al., 1999), we searched for individual frequencies of p-modes from three independent observing runs (5, 10 and 15 nights). All observations (December 1997, November 1998, January 1999) were made with the ELODIE spectrograph on the 1.93 m telescope at Observatoire de Haute Provence. The individual peaks in cleaned power spectra of each time series in the interval of excess power are compared with the predicted p-mode frequencies from stellar models (Chaboyer et al., 1999) for Procyon A.
Observations of Hysteresis Between Flare Index and Some Solar Indices
Authors: Özgüç A. , Ataç T.
Published: July 2016

Using flare index data sets for solar cycles 21 and 22 we find that flare index and some solar activity indicators show a hysteresis phenomenon. It is observed that total sunspot area, mean magnetic field and coronal index follow different paths for the ascending and descending phases of the solar cycles while saturation effect exists at the extreme phases. However, we notice that the separations between the paths are not the same during the past two cycles of 21 and 22.
Waves in the Magnetised Solar Atmosphere
Authors: Rosenthal C. S. , Carlsson M. , Hansteen V. , McMurry A. , Bogdan T. J. , McIntosh S. , Nordlund Å. , Stein R. F. , F. Dorch S. B.
Published: July 2016

We describe simulations of the propagation of waves in magnetised structures in the solar atmosphere.
Towards a Wave Theory Interpretation of Time-Distance Helioseismology Data
Authors: Birch A. C. , Kosovichev A. G.
Published: July 2016

Time-distance helioseismology, which measures the time for acoustic waves to travel between points on the solar surface, has been used to study small-scale three-dimensional features in the sun, for example active regions, as well as large-scale features, such as meridional flow, that are not accessible by standard global helioseismology. Traditionally, travel times have been interpreted using geometrical ray theory, which is not always a good approximation. In order to develop a wave interpretation of time-distance data we employ the first Born approximation, which takes into account finite-wavelength effects and is expected to provide more accurate inversion results. In the Born approximation, in contrast with ray theory, travel times are sensitive to perturbations to sound speed which are located off the ray path. In an example calculation of travel time perturbations due to sound speed perturbations that are functions only of depth, we see that that the Born and ray approximations agree when applied to perturbations with large spatial scale and that the ray approximation fails when applied to perturbations with small spatial scale.
Spatially-resolved Analysis of the Upper Convection Zone
Authors: Bogart R. S. , Schou J. , Basu S. , Haber D. A. , Hill F. , Antia H. M.
Published: July 2016

Ring-diagram analysis of MDI data has revealed systematic patterns in global flow patterns in the early phase of the cycle. We report on variations and trends seen in the flows in subsequent years.
Convective Pumping of Magnetic Fields: On the Flux Storage Problem for Solar-like Dynamos
Authors: Dorch S. B. F. , Nordlund Å.
Published: July 2016

We present results from three-dimensional numerical simulations of the interaction of stratified over-turning solar-like convection with a large-scale magnetic field: By the very nature of stellar convection, even a strong magnetic field may be held down at the bottom of the convection zone, rendering the flux storage problem obsolete. This effect may also explain the observations of some magnetically active but fully convective late type dwarf stars.
Probing Surface Flows and Magnetic Activity with Time-Distance Helioseismology
Authors: Gizon L. , Duvall T. L. , Larsen R. M.
Published: July 2016

We estimate near-surface flows using the techniques of f-mode time-distance helioseismology together with MDI/SOHO data. (1) Synoptic maps of horizontal flows are obtained for 1996, 1998 and 1999. Rotation, torsional oscillations and meridional circulation are measured. We detect weak large-scale flows converging toward active regions. Travel times are found to be shorter at locations of high magnetic activity. In addition, we measure the motion of the supergranulation pattern. (2) Realistic travel-time sensitivity kernels are used in an iterative deconvolution to infer horizontal flows at a high spatial resolution. The radial outflow outside a sunspot penumbra, called the moat, is measured.
Comparision of observed and theoretical amplitudes of oscillations above granules and intergranular lanes
Authors: Khomenko E. V.
Published: July 2016

We do modeling of the wave propagation in the solar photosphere. NLTE synthesis of the time series of the Fe I 5324 Å line profiles is performed using 3D model atmosphere. Velocity and intensity oscillations resulted from computations are compared with high spatial resolution observations. We conclulde that differences in oscillatory amplitudes above granules and intergranular lanes can be produced by variations of the physical conditions in these structures without invoking any excitation mechanisms.
Density Stratification Effects on the Thermal Convection in a Rotating Spherical Shell
Authors: Nishikawa N. , Kusano K.
Published: July 2016

The density stratification effects on the thermal convection in a rotating spherical shell, which is the representative of the solar convection zone, are investigated by three dimensional numerical simulations. It is found that, the convection structure in the strongly stratified system is switched from parallel cells aligned to the rotation axis to zonal rolles dominated by the longitudinally averaged mode, as the Rayleigh number increases much larger than the stability threshold. Corresponding to this structural transition, the averaged kinetic helicity reverses the sign in each hemisphere (from negative to positive in the northern hemisphere). The results indicate that the density stratification is much important for the nonlinear convection process in the rotating spherical shell.
Improved MLT and Its Applications to Solar Models
Authors: Li Y. , Yang J. Y.
Published: July 2016

Based on an improved MLT that takes the anisotropy and dissipation of the turbulence into account, we found that the dissipation of the turbulence in the solar convection zone should be fairly strong, while the turbulence anisotropy plays a less significant role.