bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observational Constraints on Cosmological Models
Authors: Padmanabhan T. 
Published: July 2016

AbstractCosmological models for structure formation are severely constrained by several of the recent observational results. We now have observations which probe the power spectrum of fluctuations from about 0.5 h−1 Mpc to 3000 h−1 Mpc. These probes and the constraints they imply on models for structure formation are reviewed.
3D Spectroscopy with large Telescopes: past, present and prospects
Authors: Monnet G. 
Published: July 2016

AbstractThe dimensional curse of having to pack 3D spectrophotometry data on solely 2D detectors is briefly discussed, and the main astronomical domains covered by 3D spectroscopy introduced. Finally, the scientific case for high spatial resolution 3D techniques coupled to Adaptive Optics capabilities is presented, with special emphasis on the observation of the nuclei of galaxies.
An Expanding Ring in the Gaseous Disk of NGC 6181?
Authors: Boulesteix J. , Sil’chenko O. K. , Zasov A. V. , Burenkov A. N. 
Published: July 2016

AbstractThe Sc-galaxy NGC 6181 was observed at the 6m telescope with the Fabry-Perot interferometer CIGALE in Hα emission. A ring-like zone of strong radial gas motions at the radius of 1.8 kpc was found.
Tridimensional spectroscopy of Seyfert Galaxy 3C 120
Authors: Kosugi G. , Ohtani H. , Yoshida M. , Aoki K. 
Published: July 2016

AbstractTridimensional spectroscopy of the Seyfert 1 galaxy 3C 120 was carried out with Spectronebulagraph (SNG). We constructed a data cube which is free from atmospheric variations during the scans. We then separated the blended lines by deconvolving the line profiles, to obtain pure narrow-line images and narrow-line intensity ratio diagram.
Integral field spectroscopy with optical fibres
Authors: Vanderriest C. 
Published: July 2016

AbstractAn efficient technique for obtaining complete spectral informations over moderately extended objects is to transform the geometry of their telescopic images to match a classical long ”slit” aperture. This anamorphosis is conveniently made with bundles of optical fibres. Such devices are especially useful when high spatial resolution and large wavelength coverage are required at the same time. We review the existing instruments based on this technique and present some typical results. We discuss also the future developments of integral field spectroscopy with optical fibres (visible or IR domains) for the new generation of very large telescopes.
Clues for stellar formation in NGC 1275 cooling flow
Authors: Ferruit Pierre , Pécontal Emmanuel 
Published: July 2016

Abstract3D spectrography of the inner regions of NGC 1275 has been performed using the integral field spectrograph TIGER. It revealed an association between star clusters and some line emitting gas components, likely to be filaments material. This may indicates that the clusters originate from star formation in the cooling flow
Study of Central Regions of AGNs at 6-meter Telescope
Authors: Afanasiev V. L. , Shapovalova A. I. , Burenkov A.N. , Dodonov S. N. , Vlasiouk V. V. 
Published: July 2016

AbstractKinematic investigations of the central (10″×10″) regions of the Seyfert galaxies NGC 4151 and Mkn 573 on the 6-m telescope with 3D-spectroscopy methods are presented.
Impact of nuclear activity on extended emission line regions of nearby galaxies
Authors: Pécontal E. , Ferruit P. , Wilson A.S. 
Published: July 2016

AbstractWe used the integral field TIGER to map the intensity ratios of emission lines and the velocity field over the narrow emission line of a few nearby Seyfert galaxies. Our aim is to study the impact of nuclear activity on galaxies, which will hopefully help us to probe the central engine. We present here some results for two objects: M 51 and NGC 5929.
Integral Field Spectrograph Observations of NGC 4258
Authors: Afanasiev V.L. , Courtes G. , Dodonov S.N. , Plana H. 
Published: July 2016

AbstractThe nuclear region of the NGC 4258 was observed at the 6m Telescope using an integral field spectrograph. Monochromatic maps in Ha and [NII] 6548/6583 Ålines were constructed from the data. Based on monochromatic maps and a velocity field with spatial sampling 0.6 arcsec, and the data published by Courtes et al., (1993) and Cecil et al., (1993) data, we tried to reconstruct the structure of the outflow.
Sub-resolution limit spatio-spectral information using Differential Speckle Interferometry
Authors: Lagarde S. , Sánchez L.J. , Petrov R.G. 
Published: July 2016

AbstractDifferential Speckle Interferometry (DSI) combines high angular resolution techniques with medium to high resolution spectroscopy. For non resolved sources, it yields the displacement of the object photocenter with wavelength. Combined with the spectrum s (λ), can give information with spatial and/or spectral resolution well beyond the telescope or spectrograph limits. This complementarity is illustrated here with experimental results. For the binary system Capella, we measure the angular separation, separate the spectra of the components and derive the radial velocity difference and the rotation velocity of each component. For the slowly rotating star Aldebaran we obtain the position angle of the stellar rotation axis and a relation between the angular diameter and the rotation velocity which in this case gives the latest.
Turbulent and Ordered Motions in HII Regions
Authors: Courtès G. 
Published: July 2016

SummaryThe Fill regions morphology have suggested, from the beginning of this century, the evidence of internal motions, very few gas radial velocities (RV) on the brightest “nebulae” had been obtained, because of obvious technical difficulties. The modern Fabry-Perot interferometers and the new integral Field Spectrograph provide abundant RV fields at various scales in the interstellar gas. New ways in imagery, owing to these new instruments, lead to a better analyse of both, the velocities field and their precise morphology free of stellar, dusty, and non thermal continua. The richness and the guallty of RV data, a better understanding of the expansion phenomena authorize again a rebirth of the turbulence observations of the ionized interstellar gas.
Turbulent Mixing in Wind-Blown HII Regions
Authors: Breitschwerdt D. , Kahn F.D. 
Published: July 2016

AbstractTurbulent mixing between an ionization bounded HII region and a hot shocked stellar wind (HSSW), which keeps it under pressure, is examined. Recently we have shown that acoustic disturbances can grow there to finite amplitude in a time scale which is comparable to the sound crossing time in the HII layer. The resulting turbulence will then stretch fluid elements and the frozen-in magnetic field. A condition under which turbulence can decay down to the viscous scale, where mixing is very efficient, is derived. For a uniform and plane parallel magnetic field Bo and a constant density ρo of the ambient medium, we find that efficient mixing takes place near the polar regions. Subsequently the rate of mass addition to the hot bubble is calculated and it is shown that catastrophic cooling is likely to occur. In the case of NGC 6334(A) it seems that this has just happened and we predict an upper limit for Bo of 4 x 10-5 gauss there. This model may also explain the existence of highly ionized species (e.g. OVI), soft X-rays and high velocity flows of the order of 100 km/s.
Accretion Flows in High-Mass Star Formation
Authors: Keto Eric 
Published: July 2016

AbstractWe compare observed and simulated images of the accretion flows associated with high mass star formation in the regions G10.6-0.4 and DR21. We describe, as a result of the comparison, the temperature, density, and velocity fields. Our results indicate that the G10.6-0.4 cloud core is strongly condensed and has approximately equal velocities in rotation and infall at its current evolutionary state. The rapid collapse and lack of rotational support suggests that significant angular momentum transfer is occuring over scales at least as large as those observed (0.5 pc). A milligauss magnetic field would have sufficient energy to supply the required braking torque of 1047 ergs. The DR21 core shows approximately spherically symmetric radial accretion with no detectable rotation. Unlike the G10.6-0.4 core, the DR21 core does not contain an embedded HII region. Thus this core may represent a molecular cloud condensation undergoing gravitational collapse and accretion just prior to the formation of massive stars.
Aperture Synthesis Observations of CS, NH3, and Continuum in the Bipolar Flow Source NGC2071-IRS
Authors: Kawabe R. , Kitamura M. , Ishiguro M. , Hasegawa T. , Chikada Y. , Okumura S. K. 
Published: July 2016

ABSTRACT.We have made aperture synthesis observations of CS(J=l-0, 2-1) and NH3(1,1) lines and 49, 98, and 110 GHz continuum in NGC2071-1RS with the Nobeyama Millimeter Array. Wfe have obtained maps of these lines and continuum maps with 2”. 7-20” resolution, ffe have found that dense molecular gas has a disk structure with a radial scale ranging 0.01 pc - 0.1 pc and has a ring-like structure with expanding motion at the central 5000 AU region. We also have found that there exists double dust continuum sources which are separated by 2500 AU in projection and are apparently located at the inner edges of the ring. Our observational results suggest that the disk of molecular gas has a central hole formed by wind and UV radiation from a central young stellar object, the central part is expanding, and that dust continuum emission comes from tangential parts of the shock compressed ring (r~1300 AU, M(H2)~ 21-34 Mo, and n(H2)~ 109) at the most inner side of the disk structure. The other possible model of the dust continuum sources is a binary system of self-luminous young stellar objects.
Inflow of Neutral Gas toward the Galactic Disk
Authors: Mirabel I.F. 
Published: July 2016

Summary:I highlight the evidence for inflow of neutral gas toward the disk of the Galaxy. The Milky Way is accreting 0.2-0.5 M⊙/yr of extragalactic atomic hydrogen at very high velocities. The interaction of infalling clouds with galactic material produces large-scale disturbances in the interstellar medium. Although the injection of energy into the galactic disk by infalling neutral gas is only 1% of the energy from supernovae, the impinging of high velocity neutral gas may be a relatively important source of energy in localized regions of the outer Galaxy.In the solar neighborhood the downfall rate of HI at intermediate velocities is 2.72 x 10-8z-1(kpc) M⊙pc-2yr-1, which if representative of the whole galactic disk, is at least 10 times more massive than the estimated accretion rate of extragalactic HI at very high velocities. This implies that most of the neutral gas that is infalling in the solar vicinity has originated in the galactic disk. It is concluded that in the Milky Way galaxy there is a moderate inflow of extragalactic neutral gas on top of a more intensive disk-halo circulation.
The Mass Spectrum of Interstellar Clouds
Authors: Dickey John M. , Garwood R. W. 
Published: July 2016

AbstractThe abundance of 21-cm absorption lines seen in surveys at high latitudes can be translated into a line of sight abundance of clouds vs. column density using an empirical relationship between temperature and optical depth. As VLA surveys of 21-cm absorption at low latitudes are now becoming available, it is possible to study the variation of this function with galactic radius. It is interesting to compare the abundance of these diffuse atomic clouds (with temperatures of 50 to 100 K and masses of 1 to 10 M⊙) to the abundance of molecular clouds. To do the latter we must make assumptions about cloud cross-sections in order to convert the line of sight abundance of diffuse clouds into a number per unit volume, and to convert from cloud column density to mass. The spectrum of diffuse clouds matches fairly well the spectrum of molecular clouds, although observationally there is a gap of several orders of magnitude in cloud mass. Optical absorption studies also agree well with the 21-cm results for clouds of column density a few times 1020 M⊙.
Irradiance Observations in Near-UV, Visible and Near Infrared Spectral Bands from Measurements Carried out during ATLAS-1 and EURECA-1 Missions
Authors: Thuillier Gerard , Herse Michel , Labs Dietrich , Simon Paul C. , Gillotay Didier , Mandel Holger 
Published: July 2016

For the ATLAS and EURECA missions, we have used two identical instruments to measure the absolute solar spectral irradiance from 180 to 3200 nm. These instruments are calibrated by use of a blackbody and a set of lamp standards. The measurements are carried out with 1 nm bandpass up to 800 nm and 20 nm above. The instruments and calibration procedures are described by Thuillier et al. (1981). The platform capability of instruments retrieval after measurements allows a post-flight calibration which is essential for accurate measurements. The main results obtained up to now are:- In the UV, the ATLAS-1 and EURECA-1 solar spectral irradiance are consistent with the SpaceLab 1 data obtained in 1983 (Labs et al. 1987). Figure 1 shows the ATLAS 1 and SL 1 spectra. The origin of the existing differences is presently under investigation.- In the visible domain, our measurements agree with the solar spectrum from Neckel & Labs (1984) within a few percent difference at certain wavelength.- In the IR domain, the preliminary processing shows a spectrum close to the one obtained by Thekaekara (1974).
Slowly-Varying Microwave Emissions from the Solar Corona
Authors: Tapping Ken F. , Harvey Karen L. 
Published: July 2016

Measurements of the total microwavef emission from the solar disc at single and multiple wavelengths provide a useful indicator of solar activity, and correlate well with other indices of solar activity and with solar luminosity.Since activity in the solar atmosphere is driven by the emergence, redistribution and disappearance of magnetic flux, the close and linear correspondence between the microwave flux densities, as observed at 10.7 and 21 cm wavelengths, provide a convenient and objective indicator of solar magnetic activity.Microwave emissions from the “non-flaring” solar corona originate in a wide range of sources. These generally lie in active regions, and comprise two main types: bright, compact sources a few arc-seconds across and brightness temperatures of the order of 106K, and weaker, diffuse sources arc-minutes in size and having brightness temperatures of about 104K. There is also evidence of a weaker, widespread emission covering large areas of the solar disc. The compact sources are probably due to gyroresonance, although some could be non-thermal. The diffuse widespread emission are almost certainly free-free thermal emission from plasma concentrations in the corona.The strong correlation between the 10.7 cm flux and other activity indices, even when they are produced by disimilar processes and at different heights in the solar atmosphere, may at least partially be due to the overiding role played by magnetic activity in dictating the structure of the chromosphere and corona. However, the consistent correspondences over wide ranges of activity suggest dependences upon relatively few quantities and that the microwave emission from the non-flaring Sun is dominated by a single process, which is closely and simply-related to density and temperature, such as free-free (bremsstrahlung) emission from plasma concentrations trapped in coronal and chromospheric magnetic structures. Attempts to “budget” the total microwave emission at 2.8, 10.7 and 21 cm wavelengths suggest that this is the case.Where ambient magnetic fields exceed 3000/λ Gauss, gyroresonance can produce much higher optical depths than free-free emission, and accounts for the bright emission observed in the vicinity of sunspots. Although not the dominant contributor to the total emission from the solar disc, these sources stand out brightly in high-resolution maps of active regions.To examine the assumptions of dominance of free-free thermal emission, and simple dependences upon few parameters, we compute the spectrum for a range of coronal density models, and compare the results with observations. The agreement is good, suggesting that the total disc flux is dominated by thermal, free-free emission, and that the intensity is controlled mainly by the density at the base of the corona, but is otherwise fairly tolerant of the density model used.
Possible Influence of Large Structures of Coronal Magnetic Fields on the Propagation of Solar Cosmic Rays
Authors: Fischer S. , Vandas M. , Vashenyuk E. V. 
Published: July 2016

AbstractAn investigation of mutual positions of footpoints of the Earth in the solar corona and the heliospheric current sheet (for both relativistic and nonrelativistic solar cosmic ray events) has not revealed any apparent dependence of observed SCR increases on the coronal distance of footpoints from the neutral line.
The LDE-Type Flare Occurrence (1969-1993)
Authors: Antalová A. 
Published: July 2016

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.
Magnetic Field Structures for Inverse Polarity Prominences
Authors: Schönfelder A. O. , Hood A. W. , Fiedler R. A. S. 
Published: July 2016

AbstractObservations (Leroy, 1985) have shown that most large, high prominences are of the inverse polarity type, in that the magnetic field passes through the prominence in the inverse direction to that expected from the observed photospheric field. The classic inverse polarity model of Kuperus and Raadu (1974) assumed that the prominence lies below a region of closed magnetic field lines in the neighbourhood of an O-type neutral point and above an X-type neutral point. Since the prominence must form in a low-βcoronal plasma, the pre-prominence magnetic field must have the correct topology for an inverse polarity configuration. In this paper a wide variety of different current profiles are considered in the Grad-Shafranov equation that is used to describe the equilibrium. The results of numerical solutions to the equilibrium equation indicate that a fully developed prominence will possess an O-type, but not in general an X-type neutral point.
Electron Densities in Solar Prominences
Authors: Wiik J. E. , Heinzel P. , Schmieder B. 
Published: July 2016

AbstractObservations of a quiescent prominence made with the MSDP spectrograph at the Pic du Midi Observatory provided Hαline profiles in each pixel of a 2D field of view. Comparing the absolute observed intensities with values derived from NLTE computations, we estimated the range ofelectron densitiesNe≈ 1 – 5 × 1010cm−3,source functionsS/Ic≈ 0.07 – 0.12, andoptical thicknessτ ≈ 0.3 – 8.0 within the observed prominence. Two dimensional maps of the electron densities are presented assuming two limiting values of the geometrical thickness along the line-of-sight. It is shown that if we consider geometrical thickness variations within a factor of about four, the electron density will be determined to within a factor of two, just by measuring the Hαline intensity.
Quantitative Description of the pB and Electron Density Distributions around the Inferred Neutral Line
Authors: Guhathakurta M. 
Published: July 2016

AbstractWe have investigated the three-dimensional distribution of the polarization brightness product (pB) and inferred the electron density distribution relative to the heliographic current sheet during the declining phase of cycle 20 (1973-1976). From the study we observe that the polar and current sheet densities do not vary during the last third of the cycle.
Coronal Morphology and Heating Mechanism Observations at Total Eclipses Through 1992
Authors: Pasachoff J. M. 
Published: July 2016

AbstractI describe the change of overall coronal morphology over the sunspot cycle, using most recently the total eclipse of 30 June 1992, observed from an airplane off the coast of Africa. Further, I describe a series of eclipse observations meant to test a model of coronal heating via surface Alfvén waves by searching for 1 Hz coronal oscillations in coronal loops in the green line. We plan new observations on this project during the 3 November 1994 total eclipse in South America, and discuss expedition plans.
EUV Line Diagnostics for CDS and Sumer on SOHO
Authors: Dwivedi B. N. 
Published: July 2016

AbstractThe EUV line diagnostics for the CDS and the SUMER instruments, to be flown onboard the SOHO mission, are discussed. Serts observations of EUV line intensities in an active region, reported by Thomas and Neupert (1993), have been used to determine the electron density and temperature from a theoretical curve of Mg VIII density-sensitive line ratio.
Cataclysmic Variables: Structure and Evolution
Authors: Hameury J.-M. 
Published: July 2016

AbstractI discuss the structure and evolution of cataclysmic variables, with a particular emphasis on the influence of the physics used in calculating the internal structure of the secondary. The available observational data is very rich, and can, in principle, be used to constrain the stellar physics. It is found that, in order to explain the lack of systems with periods in the range 2 – 3 hr, it is required that main sequence star become convective for masses below 0.3 M⊙. This has little consequences on the equation of state, but constrains the opacities and the treatment of subphotospheric layers.
Molecular Opacities: Application to the Giant Planets
Authors: Guillot T. , Gautier D. , Chabrier G. 
Published: July 2016

AbstractPresent available interior models of giant planets assume that the internal transport of energy is entirely convective and, accordingly, rule out any possibility of radiative transport. New opacity calculations at temperatures and densities occurring within the giant planets, taking into account H2-H2 and H2-He collision-induced absorption as well as infrared and visible absorption due to hydrogen, water, methane and ammonia are presented. These opacities are not high enough to exclude the presence of a. radiative zone in the molecular H2 envelope of Jupiter, Saturn and Uranus.
Effects of Superfluidity on Spheroidal Oscillations of Neutron Stars
Authors: Lee Umin , Collins T.J.B. , Van Horn H.M. , Epstein R.I. 
Published: July 2016

AbstractIn the limit of short wavelengths, it has been shown that superfluidity significantly affects wave propagation in neutron stars. Here we abandon the short-wavelength restriction and extend these calculations to global oscillation modes. In the present analysis, the solid crust of the neutron star is divided into an outer crust and an inner crust, and a superfluid of neutrons coexists with the solid lattice in the inner crust. We have computed several low-order global spheroidal modes for l = 2 both with and without superfluidity. We find that superfluidity in the inner crust affects the frequency spectra of acoustic (p-) modes, shear (s-) modes, and interfacial (i-) modes, although the surface gravity (g-) modes are not affected at all.