bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Distribution of Bright Galaxies
Authors: Chincarini G. , Vettolani G. 
Published: July 2016

Following a brief review of the early developments in the field, we discuss a few new advances in the distribution of bright galaxies which occured after the extensive review paper by Oort (1983) We show that the large scale structure, shells, filaments and/or sheets, may bias the determination of the velocity dispersion in clusters of galaxies and that the boundaries of the voids may often be biassed by the clusters and groups velocity dispersion.Of interest are the very large structures selected on catalogs of clusters of galaxies. The “Local Structure” claimed by Tully seems to be somewhat flattened and about parallel to the plane of the Local Supercluster. If the structure is real the alignement is relevant in relation to the physical mechanisms at work at the time of formation. Noticeable progress has been done in the measurement of the large scale velocity field. Large scale motions may somewhat bias the study of the topology of the Universe.Relevant work has be done on the shape of the boundaries of the voids and observational work is progressing to detect faint galaxies in voids and determine their charactestics. This is important also in relation to the theory of biassed galaxy formation. To better focus the observational problem and eventually related biasses, we give some statistics on dwarf galaxies in the Virgo cluster.
Observational Cosmology 1986: A summary of IAU Symposium No 124, Beijing, China
Authors: Longair M S 
Published: July 2016

“This symposium marks the real beginning of observational cosmology”, Allan Sandage, 29 August 1986.It is a pleasure to be invited to attempt to summarise the very intense work of the last 6 days. Virtually all aspects of contemporary observational cosmology have been described and debated and it is my task to try to put this wealth of new material into context. As in all such surveys, allowance must be made for personal bias - like everyone else, I am sure I am giving an unbiased view but you must judge for yourselves!
Morphology and Photometry of the UV-Excess Galaxy Pair NGC 7770/7771
Authors: Ali G. B. , I. Osman A. M. 
Published: July 2016

Morphology of the nuclear region of the component NGC 7770 indicates that it has a complicated structure in the B-band, while the V-band shows a double nuclear structure. The brightness and color of the nuclear condensations are given. Detailed photometric analysis of this component including luminosity profiles along major and minor scans as well as position angle and ellipticity curves is obtained. Integration and decomposition of the luminosity profiles are also performed. The color distribution and integrated color are also studied taking into account that the blue color together with the unusual color distribution are characteristics relevant to UV-excess galaxies. The integrated photometric parameters are also given.The state of interaction between the components of the pair is also investigated. The peculiar features appearing in the isophotal maps, the truncation of the luminosity profile along the side of interaction and the unusual appearance of the structural profiles are discussed and considered as strong evidence for the real state of interaction between the components of the pair. A lower limit of the total orbital mass of the system is found to be Mt=1.36 × 1010 M⊙, and the total mass-to-luminosity ratio is f=0.63 f⊙.
Ambartsumian's Greatest Insight - The Origin of Galaxies
Authors: Arp Halton 
Published: July 2016

From simply looking at pictures of galaxies Ambartsumian realized that new galaxies were formed in ejections from old galaxies. In the ensuing 40 years, observations have supported in increasing detail his original insight. We can now empirically outline the development of compact objects emerging from the nuclei of active galaxies into young star forming galaxies and finally into aggregates of old stars.The observations actually require galaxies to continually originate in a low particle mass plasma which has remarkably similar properties to the “superfluid” which Ambartsumian foresaw. He had the courage to present these conclusions to influential astronomers who still today reject any origin of galaxies other than in the Big Bang. In this most important subject of science, the nature of our universe, Ambartsumian's revolutionary insights are now increasingly vindicated by observation.
A Low frequency Southern Sky Survey Using the Mauritius Radio Telescope
Authors: Udaya Shankar N. 
Published: July 2016

The Mauritius Radio Telescope (MRT) is a Fourier synthesis instrument which has been built to fill the gap in the availability of deep sky surveys at low radio frequencies in the southern hemisphere. It is situated in the north-east of Mauritius at a southern latitude of 20°.14 and an eastern longitude of 57°.73. The aim of the survey with the MRT is to contribute to the database of southern sky sources in the declination range −70° ≤ δ ≤ −10°, covering the entire 24 hours of right ascension, with a resolution of 4' × 4'.6sec(δ + 20.14°) and a point source sensitivity of 200 mJy (3σ level) at 151.5 MHz.MRT is a T-shaped non-coplanar array consisting of a 2048 m long East-West arm and a 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in the South arm 16 trolleys, with four helices on each, which move on a rail are used. A 512 channel, 2-bit 3-level complex correlation receiver is used to measure the visibility function. At least 60 days of observing are required for obtaining the visibilities up to the 880 m spacing. The calibrated visibilities are transformed taking care of the non-coplanarity of the array to produce an image of the area of the sky under observation.This paper will describe the telescope, the observations carried out so far, a few interesting aspects of imaging with this non-coplanar array and present results of a low resolution survey (13' × 18') covering roughly 12 hours of right ascension, and also present an image with a resolution of 4' × 4'.6sec(δ + 20.14°) made using the telescope.
Radio Halos and Relics in Clusters of Galaxies and Detection Statistics
Authors: Giovannini Gabriele , Feretti Luigina , Govoni Federica 
Published: July 2016

New sensitive VLA observations confirm the existence of halo and relic sources in 6 Abell clusters where a diffuse emission was found in the NVSS.We find evidence that the frequency of clusters with halos and relics is larger in clusters with high X-ray luminosity. The evidence that the occurrence of a halo source is larger at high redshifts is marginal.
Spectral Mapping of Classical Double Radio Sources
Authors: Leahy J.P. , Muxlow T.W.B. 
Published: July 2016

We review the evidence that spectral curvature in the extended emission of radio galaxies is caused by synchrotron losses, and that the spatial variation can be interpreted to yield ages and expansion speeds. One of the biggest worries has been the true value of the magnetic field, but X-ray detections of inverse-Compton radiation are beginning to suggest that “minimum energy” estimates are remarkably accurate. A critical test is to compare model and observed spectra over a broad frequency range; to date this has has only been done for Cygnus A, and the results proved controversial. Here we discuss several more cases and begin to draw some general conclusions.Hotspots are usually well fitted by continuous injection models, as expected. In two cases the implied injection index is flatter than 0.5, too flat to be produced by standard Fermi acceleration in a non-relativistic shock. The bridge spectra are reasonably fitted by single-burst models, but in some objects the injection index is not constant across the lobes, showing instead a tendency to steepen in the inner bridge, where the break frequencies are lowest. The true spectral shape may be a more gradual curve than the standard models, possibly because of mixing of electron populations with different ages. Our results are limited by the inaccuracy of the absolute flux density scale, especially at low frequencies, and a fresh attack on the flux scale would be timely.
The Galactic Center at 327 MHz
Authors: LaRosa T.N. , E. Kassim Namir , W. Lazio T. Joseph , Hyman S.D. 
Published: July 2016

Figure 1 presents a wide-field, high dynamic-range, 327 MHz VLA2 image of the Galactic center (GC). This image was constructed from archival VLA data using new 3-D image restoration techniques which resolve the problem of non-coplanar baselines encountered at long wavelengths. In a recent paper (LaRosa et al. 2000) we presented a catalog of over a hundred sources from this image, 23 extended sources and 78 small-diameter sources. The catalog contains flux densities, positions, sizes, and, where possible, a 20/90 cm spectral index. We also present subimages of all the extended sources. We refer the reader to LaRosa et al. (2000) for the details. In this note we will concentrate on observations of the nonthermal filaments and briefly describe a new model for their formation.The origin and evolution of the nonthermal filaments (NTFs) observed in the GC is an outstanding problem. All of the 7 classified NTFs are visible on Figure 1: Four of these are labeled threads, the other three are the “Snake,” the “Pelican,” and the Sgr C filament. The wide-field imaging at 327 MHz lead to the discovery of the “Pelican” (Lang et al. 1999). This filament has the distinction of being the farthest NTF in projection from Sgr A and the only NTF that is parallel to the Galactic plane. One critical issue for understanding the activity and overall structure of the GC is whether these filamentary sources trace a pervasive, large-scale magnetic field or are local independent structures (e.g., Yusef-Zadeh 1989; Morris 1994, 1996; Uchida & Gusten 1995; Yusef-Zadeh, Wardle & Parastaran 1997; Shore & LaRosa 1999; Lang et al. 1999; Lang, Morris & Echevarria 1999; LaRosa et al. 2000).
Low frequency radio astronomical observations from rockets and satellites
Authors: Smith F. G. 
Published: July 2016

Observations from space vehicles of low frequency radio waves are discussed in relation to the observations made at higher frequencies from ground based observatories. It is shown that at frequencies below about 5 MHz the radiation is primarily extragalactic in origin, and that the observed values of sky brightness are consistent with the extrapolated values.An absorption effect observed at frequencies below 2 MHz appears to be isotropic and suggests that the Sun is at the centre of an H II region with emission measure 5 pc. cm-6. It is shown that if this region is contained in the Galaxy it will have a significant effect on the synchrotron radiation from the plane and on the rotation measure of polarisation of discrete sources.
Spectral Analysis of Stars on Planet-Search Surveys
Authors: Fischer Debra , A. Valenti Jeff , Marcy Geoff 
Published: July 2016

We present spectroscopic analysis of ∼1000 stars on the Lick, Keck and AAT planet search projects. This analysis provides a quantitative, and unbiased correlation between metallicity and the rate of occurrence of detected gas giant planets with orbital periods shorter than three years. As stellar metallicity increases, the occurrence of planets increases. Stars with [Fe/H] that is one third of solar only have gas giants detected ∼ 3% of the time. Stars with solar metallicity have a planet occurrence rate of 5 − 10%. The occurrence of gas giant planets rises to 20% in stars with a metallicity that is three times solar.At issue is whether the quantitative dependence of planet occurrence on metallicity is primarily an initial condition, or a by-product of accretion of gas-depleted material onto the convective zone of the star. Accretion could be distinguished as the underlying mechanism for enhanced metallicity if: 1) planet-bearing F-type stars with thinner convective envelopes show a higher mean metallicity than planet-bearing G- or K-type stars, or 2) planet-bearing sub-giants with diluted convective zones showed statistically lower metallicity than their main sequence counterparts.
Spatially Resolved STIS Spectroscopy of Betelgeuse's Outer Atmosphere
Authors: Lobel A. , Aufdenberg J. , Dupree A. K. , Kurucz R. L. , Stefanik R. P. , Torres G. 
Published: July 2016

We present spatially resolved spectra observed with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope of the upper chromosphere and dust envelope of Betelgeuse (α Orionis, M2 Iab). In the fall of 2002 a set of five high-resolution near-UV spectra was obtained by scanning at intensity peak-up position and four off-limb target positions up to one arcsecond, using a small aperture (200 by 63 mas), to investigate the thermal conditions and flow dynamics in the outer atmosphere of this important nearby cool supergiant star.Based on Mg ii h & k, Fe ii λ2716, C ii λ2327, and Al ii] λ2669 emission lines we provide the first evidence for the presence of warm chromospheric plasma at least 1 arcsecond away from the star at ∼40 R* (1 R*≃700 R⊙). The STIS spectra reveal that Betelgeuse's upper chromosphere extends far beyond the circumstellar Hα envelope of ∼5 R*, determined from previous ground-based imaging (Hebden et al. 1987).The flux in the broad and self-absorbed resonance lines of Mg ii decreases by a factor of ∼700 compared to the flux at chromospheric disk center. We observe strong asymmetry changes in the Mg ii h and Si i resonance line profiles when scanning off-limb, signaling the outward acceleration of gas outflow in the upper chromosphere.From the radial intensity distributions of Fe i and Fe ii emission lines we determine the radial non-LTE iron ionization balance. We compute that the local kinetic gas temperatures of the warm chromospheric gas component in the outer atmosphere exceed 2600 K, when assuming local gas densities of the cool gas component we determine from radiative transfer models that fit the 9.7 μm silicate dust emission feature. The spatially resolved STIS spectra directly demonstrate that warm chromospheric plasma co-exisists with cool gas in Betelgeuse's circumstellar dust envelope.
Properties of Dark Matter Halos in Disk Galaxies
Authors: de Jong Roelof S. , Kassin Susan , Bell Eric F. , Courteau Stéphane 
Published: July 2016

We present a simple technique to estimate mass-to-light (M/L) ratios of stellar populations based on two broadband photometry measurements, i.e. a colour-M/L relation. We apply the colour-M/L relation to galaxy rotation curves, using a large set of galaxies that span a great range in Hubble type, luminosity and scale size and that have accurately measured HI and/or Hα rotation curves. Using the colour-M/L relation, we construct stellar mass models of the galaxies and derive the dark matter contribution to the rotation curves.We compare our dark matter rotation curves with adiabatically contracted Navarro, Frenk, & White (1997, NFW hereafter) dark matter halos. We find that before adiabatic contraction most high surface brightness galaxies and some low surface brightness galaxies are well fit by a NFW dark matter profile. However, after adiabatic contraction, most galaxies are poorly fit in the central few kpc. the observed angular momentum distribution in the baryonic component is poorly matched by ACDM model predictions, indicating that the angular momentum distribution is not conserved during the galaxy assembly process. We find that in most galaxies the dark matter distribution can be derived by scaling up the HI gas contribution. However, we find no consistent value for the scaling factor among all the galaxies.
Scaling Laws for Dark Matter Halos in Late-Type and Dwarf Spheroidal Galaxies
Authors: Kormendy John , Freeman K. C. 
Published: July 2016

Published mass models fitted to galaxy rotation curves are used to study the systematic properties of dark matter (DM) halos in late-type and dwarf spheroidal (dSph) galaxies. Halo parameters are derived by fitting non-singular isothermals to (V2 – V2vis)1/2, where V(r) is the observed rotation curve and Vvis is the rotation curve of the visible matter. the latter is calculated from the surface brightness assuming that the mass-to-light ratio M/L is constant with radius. “Maximum disk” values of M/L are adjusted to fit as much of the inner rotation curve as possible without making the halo have a hollow core. Rotation curve decomposition becomes impossible fainter than absolute magnitude Mb ≃ −14, where V becomes comparable to the velocity dispersion of the gas. To increase the luminosity range further, we include dSph galaxies, which are physically related to spiral and irregular galaxies. Combining the data, we find that DM halos satisfy well defined scaling laws analogous to the “fundamental plane” relations for elliptical galaxies. Halos in less luminous galaxies have smaller core radii rc, higher central densities ρ0, and smaller central velocity dispersions σ. Scaling laws provide new and detailed constraints on the nature of DM and on galaxy formation and evolution. Some simple implications include:1 – A single, continuous physical sequence of increasing mass extends from dSph galaxies with Mb ≃ −7.6 to Sc I galaxies with Mb ≃ −22.4.2 – the high DM densities in dSph galaxies are normal for such tiny galaxies. Since virialised density depends on collapse redshift zcoll, ρ0 ∝ (1 + zcoll)3, the smallest dwarfs formed at least Δzcoll ≃ 7 earlier than the biggest spirals.3 – the high DM densities of dSphs implies that they are real galaxies formed from primordial density fluctuations. They are not tidal fragments. Tidal dwarfs cannot retain even the low DM densities of their giant-galaxy progenitors. in contrast, dSphs have higher DM densities than do giant-galaxy progenitors.4 – the fact that, as luminosity decreases, dwarf galaxies become much more numerous and also more nearly dominated by DM raises the possibility that there exists a large population of objects that are completely dark. Such objects are a canonical prediction of cold DM theory. If they exist, “empty halos” are likely to be small and dense -that is, darker versions of Draco and UMi.5 – the slopes of the DM parameter correlations provide a measure on galactic mass scales of the slope n of the power spectrum |δk|2 ∝ kn of primordial density fluctuations. Our preliminary results, not yet corrected for baryonic compression of DM, give n ≃ –1.9 ± 0.2. This is consistent with cold DM theory.
Magnetic Fields in Radio-Quiet Quasars
Authors: Schlickeiser R. , Crusius-Wătzel A. 
Published: July 2016

As an hypothesis the sharp far–infrared turnovers in the spectra of several radio–quiet galactic nuclei [1–3] are attributed to the modifications of synchrotron emission arising from the presence of a thermal background plasma. We calculate the synchrotron emission from a power-law distribution of relativistic electrons N(γ) = Noγ–s in a large–scale random magnetic field of strength B embedded in a thermal plasma of density ne. Two major modifications of the classical vacuum theory of synchrotron emission are established [4]:A) synchrotron sources can be optically thick only in a small frequency range around the Razin -Tsytovich frequency, whereas at smaller and higher frequencies the sources are optically thin;B) at frequencies above VR the synchrotron intensity in a plasma behaves exactly the same way as in the vacuum case, whereas at frequencies below VR the intensity is exponentially reduced,
Abundance Anomalies and Rotation in Main Sequence OB Stars
Authors: Herrero A. , Lennon D. J. 
Published: July 2016

We review the present status of our knowledge about observational evidence of the influence of rotation on the evolution and chemical surface enrichment of OB Main Sequence stars. We pay special attention to the CNO elements and show that luminosity class IV-V OB stars provide a good reference point for abundance analyses.While there is clear evidence of rotationally induced mixing in OB stars, we show that fast rotation is not a guarantee of enrichment. A comparison of observed data with present evolutionary models indicates that the observed facts can be explained assuming that the stars are born with a distribution of rotational velocities, and that depending on the stellar mass the surface abundance changes will be dominated by rotation or mass loss. Only the existence of a large number of B supergiants beyond the Main Sequence cannot be explained in this scenario. We show that current evolutionary models including rotation do not adequately account for the transfer of angular momentum from the interior to the surface.We point out that the difficulty in determining He abundances and in knowing the present or past binary status of many stars leads us to consider the above conclusions as preliminary.
Interactions between Rotation and Pulsation
Authors: Townsend Rich 
Published: July 2016

In this contribution, I will examine the interaction between stellar rotation and pulsation. I begin with a brief review of the non-rotating case, emphasizing the character of pulsations as azimuthally-propagating waves. I then go on to discuss how these waves are modified under the influence of the centrifugal and Coriolis forces. Through simple arguments, I outline the conditions under which each force can become significant in determining the wave dynamics. Particular attention is paid to the Coriolis force, since it is responsible for the formation of a waveguide, which confines the pulsation to a narrow band centered on the stellar equator. Using the example of a prograde sectoral pulsation mode, I explain the basic physical principles underlying this trapping.The Coriolis force is also responsible for the existence of Rossby waves, which are not found in non-rotating stars. I demonstrate how these waves may be understood in terms of a conservation law for angular momentum, and review their most important characteristics. I then examine how rotation modifies the frequencies of pulsation, and explain how observations of such modifications can provide information regarding a star's rotation rate. To conclude, I focus on the converse of the pulsation-rotation interaction: how the transport of angular momentum by pulsation might be important in determining the evolution of a star's rotation profile.
IR Mergers/Qsos with Galactic Winds
Authors: Lípari S. , Dottori H. , Mediavilla E. , Terlevich R. , Diaz R. , Taniguchi Y. , Garcia-Lorenzo B. , Acosta-Pulido J. , Zheng W. 
Published: July 2016

We report, as a part of a long-term study of IR mergers and IR QSOs, detailed spectroscopic evidences for outflow (OF) features in nearby IR mergers/QSOs (with low and extreme velocity OF, LVOF and EVOF, respectively). We found EVOF in IRAS 01003-2238, 11119+3257, 13218+0552, 14394+5332, 15130-1958 and 15462-0450. The low velocity OF components were detected mainly in objects with starburst processes. Meanwhile the EVOF were found mainly in objects with obscured IR QSOs plus strong starbursts.HST images of IR+BAL+Fe II QSOs show in practically all of these objects “arc or shell” features probably associated to galactic winds (GW) and/or merger processes. We present also new results of a study of the morphology, kinematics and ionized structure of IR mergers/QSOs with GW. This new study is based mainly in INTEGRAL two-dimensional (2D) fibre spectroscopy (obtained at La Palma 4.2 m telescope).