bluuebunny/crossref_metadata_2025 huggingface dataset:
Quasar Mesolensing as a Probe of CDM Substructures
Authors: Yonehara Atsunori , Umemura Masayuki , Susa Hajime
Published: July 2016

Currently, the CDM scenario has met a crisis that the number of substructures presented by cosmological N-body simulations based on the scenario is much larger than the observed amount. If such substructures do not really exist, it must be an actual crisis for the CDM scenario. in contrast, if the reason for the overproduction of substructures in simulations is some observational bias, and many substructures are invisible or not detectable due to very low star formation efficiency by some feedback processes (e.g., Nishi & Susa 1999), the CDM scenario will survive. Thus, it is crucial for the resolution of this crisis to discriminate between these two possibilities.
The dark matter halos of spheroidal galaxies and clusters of galaxies
Authors: Treu Tommaso , Koopmans Léon V. E. , Sand David J. , Smith Graham P. , Ellis Richard S.
Published: July 2016

We describe the first results from two observational projects aimed at measuring the amount and spatial distribution of dark matter in distant early-type galaxies (E/S0s) and clusters of galaxies. At the galaxy scale, the Lenses Structure and Dynamics (LSD) Survey is gathering kinematic data for distant (up to z ⋐ 1) E/S0s that are gravitational lenses. A joint lensing and dynamical analysis constrains the fraction of dark matter within the Einstein radius, the mass-to-light ratio of the stellar component, and the total slope of the mass density profile. These properties and their evolution with redshift are briefly discussed in terms of the formation and evolution of E/S0 galaxies and measurement of the Hubble Constant from gravitational time delay systems. At the cluster scale – after careful removal of the stellar component with a joint lensing and dynamical analysis – systems with giant radial arcs can be used to measure precisely the inner slope of the dark matter halo. An HST search for radial arcs and the analysis of a first sample are briefly discussed in terms of the universal dark matter halos predicted by CDM simulations.
Orbital structure of triaxial galaxies
Authors: van de Ven Glenn , Verolme Ellen , Cappellari Michele , de Zeeuw Tim
Published: July 2016

We have developed a method to construct realistic triaxial dynamical models for elliptical galaxies, allowing us to derive best-fitting parameters, such as the mass-to-light ratio and the black hole mass, and to study the orbital structure. We use triaxial theoretical Abel models to investigate the robustness of the method.
ERO R1 in the field of CL0939+4713 – Evidence for an SO-like galaxy at z ~ 1.5
Authors: Iye M. , Kashikawa N. , Imanishi M. , Kodama T. , Chiba M. , Shimasaku K. , Okamura S. , Miyazaki S. , Simpson C. , Kobayashi N. , Terada H. , Goto M. , Iwamuro F.
Published: July 2016

An elongated ERO with R - K′ = 7.5 behind the cluster A851 at z=0.4 was found to lie at z = 1.5 both by the photometric redshift and by a cross correlation method of its H-band SED with local E/SO spectra. the luminosity profile is well represented by a seeing convolved exponential disk, and the lack of redshifted H-alpha emission indicates that it has a dynamically relaxed disk with an old stellar population. Gravitational lensing of the cluster is not strong enough to stretch the image and cannot convert the de Vaucouleurs law into an exponential law.
Galactic Disk Surface Density in the Solar Neighbourhood
Authors: van Altena William F. , Korchagin Vladimir I. , Girard Terrence M. , Dinescu Dana I. , Borkova Tatiana V.
Published: July 2016

Using parallaxes and proper motions of a kinematically and spatially unbiased sample of old bright red giant stars from the Hipparcos catalog with measured radial velocities from Barbier-Brossat & Figon (2000), we have re-estimated the surface density of the Galactic disk in the solar neighbourhood within ±0.4 kpc of the Sun. We determine the vertical distribution of the red giants as well as the vertical velocity dispersion of the sample, (14.4±0.26 km/sec), and combine these to derive the surface density of gravitating matter in the Galactic disk. Using these data, we determine the surface density of the galactic disk as a function of the galactic coordinate, z. the surface density of the disk increases from 10.5 ±0.5 M⊙within ±50 pc to 42 ±6 M⊙/pc2 within ±350 pc. The volume density of the galactic disk within ±50 pc is 0.105±0.005 M⊙/pc3, which is only marginally greater (within 2 sigma) than the volume density estimates of observed baryonic matter in the solar neighbourhood.
Rotating Halos and Heavy Disks: The Case of NGC 2915
Authors: Masset Frédéric S. , Bureau Martin
Published: July 2016

NGC 2915 is a blue compact dwarf galaxy embedded in an extended, low surface brightness HI disk with a bar and two-armed spiral structure. Common mechanisms are unable to explain those patterns and disk dark matter or a rotating triaxial dark halo were proposed as alternatives. Hydrodynamical simulations were run for each case and compared to observations using customized column density and kinematic constraints. the spiral structure can be accounted for by an unseen bar or triaxial halo, but the large bar mass or halo pattern frequency required make it unlikely that the spiral is driven by an external perturber. in particular, the spin parameter lambda is much higher than predicted by current CDM structure formation scenarios. Massive disk models show that when the gas surface density is scaled up by a factor of about 10, the disk develops a spiral structure matching the observed one in perturbed density as well as velocity. This suggests that the disk of NGC 2915 contains much more mass than is visible, tightly linked to the neutral hydrogen. A classic (quasi-)spherical halo is nevertheless still required, as increasing the disk mass further to fit the circular velocity curve would make the disk violently unstable
The Opacity of Spiral Galaxies from Counts of Distant Background Galaxies
Authors: Holwerda B.W. , González R.A. , Allen R. J. , Van Der Kruit P.C.
Published: July 2016

We have applied the “Synthetic Field Method” on a sample of 20 nearby galaxies in order to determine the opacity of their disks. We present preliminary results on the radial dependence of cold dust absorption for 3 examples. the spirals NGC 4535 and NGC 4725 show significant absorption at a half-light radius. UGC 2302, a LSB galaxy, shows much less opacity.
The Central Dynamics of Blue Low Surface Brightness Galaxies
Authors: Zackrisson Erik , Bergvall Nils
Published: July 2016

We use optical, long-slit rotation curves to derive the slope of the central density profile in three blue disk galaxies with very faint central surface brightness values. We find the result to be in conflict with current cold dark matter predictions and to lend further support for pseudo-isothermal spheres as superior models for the dark halos of galaxies.
Kinematics of Extremely Faint Dwarf Galaxies
Authors: Begum Ayesha , Chengalur Jayaram N.
Published: July 2016

We present the results of deep, high velocity resolution (~1.6 km s−1) Giant Meterwave Radio Telescope (GMRT) HI 21 cm observations of extremely faint (Mb > −12.5) dwarf irregular galaxies. We find that all of our sample galaxies show systematic large scale velocity gradients, unlike earlier studies which found chaotic velocity fields for such faint galaxies. For some of the sample galaxies the velocity fields are completely consistent with ordered rotation, though the peak circular velocities are comparable to the observed random motions. These are the faintest known galaxies with such regular kinematics. We present (“asymmetric drift” corrected) rotation curves and mass models (including fits for Isothermal and NFW halos) for some of these galaxies and discuss the implications for hierarchical models of galaxy formation.
HI Rotation of Dwarf Galaxies with Unusually High HI Mass-to-Light Ratios
Authors: Warren Bradley E. , Jerjen Helmut , Koribalski Bärbel S.
Published: July 2016

We present here preliminary results of a multi-wavelength investigation into high HI mass-to-light ratio dwarf galaxies identified in the HIPASS Bright Galaxy Catalog. Here we focus on the rotational properties of some of the galaxies.
Tully-Fisher Relations from an HI-Selected Sample
Authors: Meyer Martin J. , Zwaan Martin A. , Webster Rachel L. , Schneider Stephen E.
Published: July 2016

The Tully-Fisher relation is of interest because of its use as a secondary distance measure and the constraints it places on the physics of rotationally supported galaxies. We use data from the HI Parkes All-Sky Survey Catalogue to study and apply the Tully-Fisher relation on a sample of galaxies selected on their HI properties. the issues of third parameter dependencies and intrinsic scatter of the Tully-Fisher relation are investigated.
The Tully-Fisher Relation for Hickson Compact Groups
Authors: Amram Philippe , De Oliveira Claudia Mendes , Plana Henri , Balkowski Chantal
Published: July 2016

We investigate the properties of the B-band Tully-Fisher (TF) relation for 25 compact group galaxies, usingVmaxderived from 2-D velocity maps. Our main result is that the majority of the Hickson Compact Group (HCG) galaxies lie on the TF relation, although with large scatter. However, 20% of the galaxies, including the lowest-mass systems, seem to have higher B luminosities, for a given mass, or alternatively, a mass which is too low for their luminosities. We favour the scenario of brightening of the outliers due to either enhanced star formation or merging, rather than truncation of the dark halo due to interactions, to explain the position of the outliers on the TF relation.
Measuring Dark Matter Halos by Modeling Interacting Galaxies
Authors: Theis Christian
Published: July 2016

The richness of tidal features seen in interacting galaxies allows for the determination of their characteristic parameters, provided one can deal with the extended parameter space. Genetic algorithm based methods – like our code minga – have proven to be such a tool. Here I discuss the implementation of dark matter halo descriptions in the restricted N-body simulations of minga. I show that the final morphology of a galaxy encounter strongly depends on the halo properties. Thus, modeling tidal features of interacting galaxies might allow also for conclusions on the galactic dark matter content.
Orbit Evolution of Satellite Galaxies in Dark Matter Haloes
Authors: Just Andreas
Published: July 2016

We investigate the effect of the inhomogeneity of the background distribution on dynamical friction. We find a generalised Coulomb logarithm with position dependent maximum impact parameter scaling with the local scale length, which is usually much smaller than the distance to the centre of the background system. We apply the new formula to N-body calculations of satellite galaxies in Dark Matter haloes and find a systematic improvement of the orbit fits. Additionally a first order force not parallel to the motion of the massive object appears, which can be neglected at least in spherical systems due to the lack of a secular effect.
Accurate (In)Direct Detection Rates for Neutralinos
Authors: Schelke Mia , Edsjö Joakim , Ullio Piero
Published: July 2016

Neutralinos arise as natural cold dark matter candidates in many supersymmetric extensions of the Standard Model of particle physics. If Galactic neutralinos exist, they could in principle be detected by both direct and indirect detection techniques. We use the DarkSUSY package to make very accurate calculations of the expected detection rates for a wide scan of parameter values. We compare the calculations with the sensitivity of current and future detectors, and conclude that some of the models are above the sensitivity limits. Comments are also made on the mutual dependence between the halo profile and the detection rates.
The Magnetic Field of the Sun: An Object Lesson
Authors: Parker E. N.
Published: July 2016

The magnetic field of the sun is created by a magnetohydrodynamic dynamo under conditions bearing some qualitative similarities to the apparent generation of the galactic field in the gaseous disk of the galaxy. There is a similarity, too, in the extension of bipolar lobes of the solar field above the surface of the sun and the extension of bipolar lobes of the galactic field outward from both sides of the disk. Hence one can learn a lot about the expected origin and activity of the galactic field by studying the behavior of the magnetic field of the sun. In particular, the mysteries associated with the “simple” circumstances of the origin of the solar magnetic field far below the surface are no less than the mysteries in the theoretical origin of the galactic field, where there is so little direct observation of the small scale motions and magnetic fields. There is reason to think that the activity of the magnetic field of the sun, producing prominences, flares and X-ray corona, a solar wind, and coronal mass ejection may all have counter parts in the activity of the galactic field above the surface of the gaseous disk.
CoMStOC: The Coronal Magnetic Structures Observing Campaign
Authors: Schmelz J.T.
Published: July 2016

The Coronal Magnetic Structures Observing Campaign (CoMStOC) was designed to measure the magnetic field strength and determine its structure in the solar corona. Simultaneous soft X-ray and microwave data separate the contributions of the two dominant microwave emission mechanisms - gyroresonance and thermal bremsstrahlung. Where gyroresonance dominates, the magnetic field can be determined.
Masers and Stellar Magnetic Fields
Authors: Reid Mark J.
Published: July 2016

Observations of circular polarization of molecular masers associated with late type giant and supergiant stars can be used to estimate the magnetic field strength in the masing region. Magnetic field strengths of ~ 5 mG are deduced for OH masers in circumstellar envelopes at distances of ~ 1016 cm from the star, and magnetic field strengths of ~ 50 G are deduced for SiO masers that reside above the photosphere. Extrapolation to the stellar photosphere suggests that average surface magnetic fields are on the order of 103 G.
Correlation Between Galactic Non-Thermal Continuum Emission and HI-Column Density
Authors: Beuermann K. , Kim Y.G.
Published: July 2016

The distribution of magnetic field strengths in the interstellar gas is an important datum which relates to the formation of dense cloud complexes as well as to the distribution and propagation of cosmic rays. Brown and Chang (1983) found the brightness temperature of the radio continuum emission to be correlated with the HI column density NH and deduced a field strength which increases with particle density as  ~ 0.44. Troland and Heiles (1986) critized their approach and pointed out that Zeeman measurements suggest no increase in field strength for particle densities n ≤ 100 H-atoms cm-3.
A Detailed Model of the Distribution of Synchrotron Emission in the Galactic Disk
Authors: Broadbent A. , Haslam C.G.T. , Osborne J.L.
Published: July 2016

A technique for separating the radio continuum emission of the Galaxy into its thermal and nonthermal components has been recently developed by Broadbent, Haslam and Osborne (1989). In this the thermal component is identified by its detailed correlation with the 60 μm infrared emission as observed by IRAS after the subtraction of zodiacal light and the HI-associated dust emission. This technique has been applied to the 408 MHz allsky survey of Haslam et al. (1982). A model of the distribution of synchrotron emissivity in the galactic disk has then been derived including information on the other tracers of spiral structure (HI, CO and giant HII regions) in order to account in detail for the observed nonthermal emission. The spiral arm pattern has two pairs of arms emanating from a central ellipse. The function describing the underlying variation of synchrotron emissivity with galactocentric radius is zero at the centre, rises to a sharp peak and then falls off slowly beyond 3 kpc. Using a scale length of the variation of cosmic ray electron density derived from γ-ray observations, we find that the scale length of the magnetic field variation must be as long as 22 kpc. This agrees with the scale length derived assuming equipartition between energy densities of magnetic field and cosmic rays. The variation of emissivity with height above the plane deduced by Phillipps et al. (1981) when included in our model gives good fits to the observed cuts across the plane. We have modelled the variation of the galactic magnetic field across a spiral arm as a gaussian. In order to fit the peaks in the galactic plane profile σ=0.2 kpc and a maximum compression of the field in the arm of 3.5:1 is required. These parameters are compatible with the results of N-body simulations of spiral arm formation which treat gas clouds as the unit particles. A detailed description of the model is about to be submitted for publication.
The Magnetic Field of the Galaxy in the Solar Vicinity and the Polarization of Stars
Authors: Makarov A.N. , Andreassian R.R.
Published: July 2016

The results of a study of the magnetic field of the Galaxy up to ~3.5 kpc from the Sun by the analysis of interstellar polarization of optical radiation of catalogue stars (Mathewson et al., 1978) are presented. For the regions 90° < l <180° and 300° < l < 360°, where the polarization degree P is maximum, the empirical form

is found.
Polarization and Magnetic Fields in Supernova Remnants
Authors: Milne D.K.
Published: July 2016

Observations of polarization in and around Galactic supernova remnants, the deduced Faraday rotation and magnetic fields and their interpretation are reviewed. There are some indications of interaction with the Galactic magnetic field, but the conclusions are that this is an aspect which would benefit from considerably more observation and theoretical modelling.
The Magnetic Field of the Crab as Revealed by New, High Resolution, Multi-Band Radio Images
Authors: Bietenholz M. F. , Kronberg P. P.
Published: July 2016

We present and describe recent radio observations of the Crab Nebula, which allow us to determine the magnetic field orientation and depolarization at unprecedented resolution. The observations were made in 1987-1988 using all four configurations of the VLA, at 1410,1515,4625, and 4885 MHz. The resulting maps were all convolved with a clean beam of 1.8″ × 2.0″, elongated in P.A. 80°, and the residuals added back in.
Dynamo in Astrophysics
Authors: Ruzmaikin A.A.
Published: July 2016

The fast dynamo acting in a turbulent flow explains the origin of magnetic fields in astrophysical objects. Stellar cycles and large-scale magnetic fields in spiral galaxies reflect the behaviour of a mean magnetic field. Intermittent magnetic structures in clusters of galaxies are associated with random magnetic field.
Galactic Dynamos Without Sharp Boundaries: Non-Axisymmetric Fields in Axisymmetric Disks?
Authors: Meinel R. , Elstner D. , Rüdiger G. , Krause F.
Published: July 2016

Radio polarization observations of spiral galaxies suggest the existence of large-scale galactic magnetic fields which are of either axisymmetric -spiral (ASS) or bisymmetric-spiral (BSS), i.e. non-axisymmetric, structure (cf. Beck, 1939). Clear evidence for a BSS field was indicated for M31 by M. Krause et al. (1989).
Phenomena Involving Magnetic Vortex Tubes
Authors: Browne P.F.
Published: July 2016

Magnetic vortex tubes (MVTs) on a hierarchy of scales occur universally. On the largest scale they channel bipolar outflows of gas. A pinched region of MVT provides an acceleration mechanism capable of yielding the maximum cosmic ray energies.
Magnetic Field in a Turbulent Galactic Disk
Authors: Otmianowska-Mazur K.
Published: July 2016

A numerical model of magnetic field structure in the presence of turbulent motions of the interstellar gas has been made. We solved the kinematic equation of magnetic field transport in a limited volume of ISM. Diffusion effects smoothing out small-scale structure are allowed as well. A permanent helical configuration of field lines has been found. This justifies, at least partly, searching solutions in the dynamo theory in the form of field modes. The presence of diffusion appears essential for the time evolution of magnetic field and magnetic energy density.
CO Observations of a Region with Strong Polarization in M31
Authors: Bajaja E. , Berkhuijsen E.M. , Beck R.
Published: July 2016

A region with strong radio polarization in the SW of M31 was observed in the 12CO(1–0) line. The results are compared with the radio continuum, HI and Ha. The CO emission appears to be correlated with the total radio emission, but anticorrelated with the polarized intensity.
Polarization in the Magellanic Clouds
Authors: Haynes R.F. , Wayte S. , Harnett J.I. , Klein U. , Wielebinski R. , Buczilowski U.R. , Bajaja E. , Malin D. , Murray J.D. , Hunt A.J. , Wark R. , Sciacca L.
Published: July 2016

We present new results from a number of deep radio polarization surveys of the Magellanic Clouds at 2.3 GHz, 4.75 GHz and 8.55 GHz. Extended linearly polarized radio emission has been found at 2.3 and 4.75 GHz from both galaxies.
Linearly Polarised Radio Emission from M83 (NGC 5236) and NGC 891
Authors: Sukumar S. , Allen R.J.
Published: July 2016

Recent VLA 20 cm radio continuum observations of the southern face-on barred spiral M83 reveal that the magnetic field is very highly aligned at the outer regions (~12 kpc radius) and totally disrupted in the inner regions (<6 kpc) of the galaxy. The RM variation suggests an axisymmetric morphology for the magnetic field. VLA 6 cm continuum polarization observations of the edge-on spiral NGC 891 reveal ordered magnetic fields at large Z-distances (~3 kpc) from the galactic plane, probably emanating from the disk through instabilities.
Magnetic Fields and Star Formation for the ANS Sample of Galaxies
Authors: Stryczynski J.
Published: July 2016

From the literature we collected radio and magnetic field data for the ANS spiral galaxies. We suggest that the groups of objects, as revealed in the UV range, do not differ in magnetic field strength, although statistics of the sample are very poor.
Magnetically Controlled Gravitational Instabilities in the Taurus Molecular Complex
Authors: Shuter W.L.H. , Dickman R.L.
Published: July 2016

The periodic structure we [1,2] have previously reported as puzzling in the velocity field and column density of 21 cm self–absorption in the Taurus Complex, can be explained naturally in terms of the gravitational collapse of the HI along the lines of force of the large–scale magnetic field of the region.
Jet Interactions with Molecular Clouds: C–Shock Models
Authors: Smith M.D. , Brand P.W.J.L.
Published: July 2016

Molecular hydrogen emission lines are associated with collimated outflows from young stellar objects. They have been measured near Herbig–Haro objects within jets as well as at the jet termination. Similarly to HH objects, the lines are produced from radiative shocks which may be in the form of oblique internal jet shocks or bow shocks. A J-shock can only be invoked in a dynamical model context since the H2 lines are often wide (> 30 km s−1). The alternative is the MHD C–shock in which the ionisation level is sufficiently low so that the magnetic field and ions interact weakly with the neutrals. We have investigated C-shock flows by employing approximate forms for the ion-neutral drag, cooling and other processes with the following results.
MHD Simulations of Mass Outflows from Star Forming Regions
Authors: Stone James M. , Norman Michael L. , Mihalas Dimitri
Published: July 2016

We have begun a project to produce self-consistent 2-D MHD simulations of the generation and collimation of mass outflows from star forming regions. We describe our code development work, and present preliminary results.
The Collimation of MHD Winds: Bipolar Flows and Jets
Authors: Norman Colin A. , Heyvaerts Jean
Published: July 2016

We show that axisymmetric magnetized winds emanating from rotating stars, disks, tori, etc. generally tend to collimate along the symmetry axis and conjecture that this is the reason there are so many bipolar flows and jets. The actual form of the flows at large distances from the source are either cylindrical or paraboloidal depending on the total poloidal current.
Cosmic Ray Acceleration and γ Ray Induced by the Interaction of the Ejecta of SN1987A with the Magnetized Cloud
Authors: Hanami Hitoshi
Published: July 2016

We have studied the high energy physical process related to the cosmic ray acceleration for SN1987A. The X-ray flare observed by Ginga satellite (Makino 1988) and TeV γ-rays reported by the JANZOS collaboration (Bond et al. 1988) occurred in January, 1988. These events may be explained by the interaction of the supernova ejecta with the surrounding cloud, which induces the thermalization of shocked material and the acceleration of cosmic ray on the reverse shock at the front of cloud. Especially, the soft X-ray emission from SN1987A is well described by the interaction model of the ejecta with the circumstellar medium (Masai et al. 1988, and Yoshida and Hanami 1988). It seems to be natural to consider that the origin of the γ-ray is connected with that of the X-ray flare, since they had occurred at same time. Then, we consider about the relation of this acceleration mechanism and the evolution scenario of the progenitor.
The Large-Scale Magnetic Field Structure Near the Galactic Centre
Authors: Reich Wolfgang
Published: July 2016

High frequency polarization observations reveal the existence of a poloidal magnetic field structure in the Galactic Centre region on scales of about 200 pc. At lower frequencies large non–thermal spurs are seen tracing the magnetic field up to kpc distances from the Galactic Centre.
Zeeman Observations of the Magnetic Field in the Galactic Centre
Authors: Schwarz U. J. , Lasenby J.
Published: July 2016

Direct measurements of the magnetic field in the neutral ring at the Galactic centre were made by observing the Zeeman splitting in HI- absorption around ± 100 kms−1 and give a field of (–0.5mG ± 0.17mG); significantly less than inferred from IR polarisation observations (Werner et al., 1988).
Polarization Properties of Radio Cores
Authors: Saikia D. J.
Published: July 2016

Extragalactic radio sources associated with elliptical galaxies and quasars exhibit a rich variety of structures on scales ranging from < few parsecs to over a Mpc. The sources with extended (> tens of kpc) structure are often classified into the low–luminosity FRI sources which usually have diffuse outer lobes, and the high luminosity FRII sources which tend to have bright hotspots at the outer edges. (Miley 1980; Bridle & Perley 1984). The FRI and II types differ in a number of other aspects as well such as the structure and magnetic field orientation in the radio jets, morphology of the parent optical galaxies and their environments (Bridle & Perley 1984; Lilly & Prestage 1987; Owen and Laing 1989). It therefore seems unlikely that the two FR classes either represent different phases in an evolutionary sequence or are caused by differences in orientation or the supply of energy to the outer lobes.
Gravo-Magnetodynamic Engine for Cosmic Jets
Authors: Uchida Yutaka
Published: July 2016

There is a long-standing mystery about the formation of the jets and lobes from AGN's. In the present paper, a “gravo-magnetodynamic” picture is proposed for the production of the jets and lobes from AGN's: The primordial large scale magnetic field, which is squeezed by the gravitational contraction of the material to the central object, serves in driving out the spinning jets in bipolar directions, and at the same time, serves as a drain extracting angular momentum of the disk material, enhancing the accretion and therefore enhancing the liberation of the gravitational energy at the center.
Polarization Observations of Selected Radio Galaxies at 327 Mhz
Authors: Willis Anthony G. , O'dea Christopher P.
Published: July 2016

We have measured the distribution of polarized emission from the radio galaxies NGC315, NGC6251, DA240, 3C236 and 3C326 at 327 MHz (92 cm wavelength) with the Westerbork Synthesis Radio Telescope (WSRT). These radio galaxies were all selected for observation because they exhibited degrees of polarization as high as 60 or 70 percent at 610 MHz (49 cm wavelength) and because they all have angular sizes greater than about 20 arcmin. Therefore they are still well-resolved by the WSRT at 92 cm wavelength. All sources in the sample exhibit significant linear polarization at 92 cm wavelength. Some depolarization does occur in NGC315 and 3C326 but parts of 3C236, DA240 and NGC6251 appear not to depolarize to 92 cm. Assuming an ordered, equipartition magnetic field, we find that the density of thermal depolarizing material in these radio galaxies is very low, typically about 1 × 10−5 cm−3 or less. Therefore these radio galaxies may represent distributions of pure magnetic fields and relativistic particles on scales of several hundred kiloparsecs or more.
Search for Extragalactic Radio Sources with Large Rotation Measure
Authors: Aizu Ko , Inoue Makoto , Tabara Hiroto , Kato Tatsnji
Published: July 2016

Intrinsic large rotation measures (RM) were searched for 128 extragalactic sources based on polarization data obtained at the NRO 45–m telescope. The number of sources with RM > 500 rad m−2 is only seven.
Asymmetric Depolarization in Double Radio Sources
Authors: Garrington S. T. , Conway R. G. , Holmes G. F.
Published: July 2016

The asymmetric depolarization seen in powerful extragalactic double sources with one sided jets may be explained in terms of differential Faraday effects in a halo of gas surrounding the source, provided the halo has a core-radius ~30–100 kpc, and contains a magnetic field of order >1 μGauss tangled on a scale <5 kpc.
Magnetic Field Generation in Protogalactic Halos
Authors: Pudritz Ralph E.
Published: July 2016

It has become quite clear that dynamically significant magnetic fields of order 10−6 Gauss are present in galactic halos (Perry, these Proceedings) at redshifts up to z ≥ 2. Comparable fields have been detected on cluster and even on supercluster scales (Giovannini, these Proceedings). The existence of such high fields is surprising because it is highly unlikely that primeval magnetic fields could have been much stronger than 10–18 Gauss. These observations require that there be an epoch of very vigorous dynamo action that can amplify this seed primordial field up to the observed values. Since strong fields are already in place by redshifts of z ≃ 2, this amplification process must operate very quickly. This argues against the idea that such fields could be generated on huge intercluster scales since the dynamical times are far too long. A much more promising site for the dynamo process is in the dark matter halos of young galaxies during the epoch of galaxy formation. The fundamental point is that vigorous dynamo action can take place in shocks that are expected to occur throughout the dark matter potential wells of protogalaxies (Pudritz and Silk 1989 (≡ PS), Pudritz 1989).
Imaging in Hard X-ray Astronomy
Authors: Li T. P.
Published: July 2016

The energy range of hard X-rays is a key waveband to the study of high energy processes in celestial objects, but still remains poorly explored. In contrast to direct imaging methods used in the low energy X-ray and high energy gamma-ray bands, currently imaging in the hard X-ray band is mainly achieved through various modulation techniques. A new inversion technique, the direct demodulation method, has been developed since early 90s. with this technique, wide field and high resolution images can be derived from scanning data of a simple collimated detector. The feasibility of this technique has been confirmed by experiment, balloon-borne observation and analyzing simulated and real astronomical data. Based the development of methodology and instrumentation, a high energy astrophysics mission – Hard X-ray Modulation Telescope (HXMT) has been proposed and selected in China for a four-year Phase-A study. The main scientific objectives are a full-sky hard X-ray (20–200 keV) imaging survey and high signal-to-noise ratio timing studies of high energy sources.
Point X-Ray Sources in the Supernova Remnant RCW 86
Authors: Gvaramadze Vasilii V. , Vikhlinin Alexey A.
Published: July 2016

We have discovered two point X-ray sources in the southwest protrusion of the supernova remnant (SNR) RCW 86. One of them is interpreted as a foreground active star, while the second one as a candidate neutron star associated with the SNR.
Correlation between the X-ray Spectra of Young Pulsars and their Wind Nebulae
Authors: Gotthelf E. V.
Published: July 2016

A significant correlation is discovered between the X-ray spectra of young pulsars (PSRs) and that of their associated wind nebulae (PWNe). For a sample of nine bright Crab-like pulsar systems observed with the Chandra X-ray observatory, we report a linear relationship between the photon indices for the PWNe and those of the phase-averaged pulsar emission, where ΓPWN = 0.72 ± 0.13 × ΓPSR + 0.86 ± 0.20. Furthermore, we find that the spectral slopes of younger, more energetic, pulsars tend to be steeper. These results confirm a consistent pulsar emission mechanism and provide important new observational constraints on the current theory of shock acceleration models for pulsar wind emission.
Pulsar Spin-Down by 3P2 Superfluid Neutrons
Authors: Luo Xin-Lian , Peng Qiu-He , Zhang Ming , Chou Chih-Kang
Published: July 2016

To describe pulsar spin-down, a simple combined torque model, that takes into account both the standard magnetic dipole radiation and the electromagnetic radiation from the 3P2 superfluid vortex neutrons inside neutron star, is presented. Using an ordinary exponential model for the magnetic field decay, we investigate pulsar evolution tracks on the diagram, which is quite different from that of the standard magnetic dipole radiation model, especially when the superfluid torque or field decay become dominate.
Modelling X-ray and Gamma-ray Emission from Pulsars
Authors: Rudak B. , Dyks J.
Published: July 2016

Lightcurves and broadband energy spectra of the brightest X/γ-ray sources among the rotation powered pulsars exhibit unexpected richness of features, making each object almost a unique case. This contribution presents how our models of high-energy radiation within the framework of SCLF (space charge limited flow) polar-cap scenarios tackle with some of these challenges.
Strange Quark Stars — A Review
Authors: Xu R. X.
Published: July 2016

A pedagogical overview of strange quark matter and strange stars is presented. After a historical notation of the research and an introduction to quark matter, a major part is devoted to the physics and astrophysics of strange stars, with attention being paid to the possible ways by which neutron stars and strange stars can be distinguished in astrophysics. Recent possible evidence for bare strange stars is also discussed.
The Relation between Spin and Orbital Periods in HMXBs
Authors: Liu Q. Z. , Li X. D. , Wei D. M.
Published: July 2016

The relation between the spin period (Ps) and the orbital period (Po) in high-mass X-ray binaries (HMXBs) is investigated. In order for Be/X-ray binaries to locate above the critical line of observable X-ray emission due to accretion, it is necessary for an intermediate orbital eccentricity to be introduced. We suggest that some peculiar systems in the Po − Ps diagram are caused by their peculiar magnetic fields.
Accretion Disk Oscillations and QPOs in Black Hole X-ray Binaries
Authors: Wu Xue-Bing
Published: July 2016

The observed quasi-periodic oscillations (QPOs) in low-mass X-ray binaries have been suggested to be probably related to the characteristic oscillation modes in the inner part of a relativistic accretion disk. Here we study the non-damping oscillation modes in the disk by considering the local perturbations and viscosity effects. We find that the trapped oscillations are amplified significantly when the viscosity parameter increases and the trapped size varies when the radial wavenumber and Mach number change. Our results support that the hundred-hertz QPOs and their low fractional rms amplitudes found in some black hole X-ray binaries may be explained by the trapped non-damping oscillation modes in the inner part of an accretion disk around a rapidly rotating black hole.
New Chandra/HST-STIS Results on Seyfert I AGN: Photoionized Outflows
Authors: McKernan Barry , Yaqoob Tahir
Published: July 2016

We present soft X-ray results from observations with Chandra (HETGS) of the Seyfert I AGN NGC 4593 and Mrk 509. We discuss the photoionized outflows associated with Seyfert I AGN in terms of their absorption spectral signatures and discuss their kinematics, column density and ionization state. We discuss the link between UV and X-ray absorbers in Mrk 509 (which was simultaneously observed with Chandra and HST-STIS). We also briefly discuss the possibility of absorption due to neutral Fe embedded in the warm absorber of NGC 4593 versus an interpretation of the data in terms of soft X-ray relativistic emission lines. We conclude with a summary of what is being learnt about warm absorbers in type I AGN from high resolution spectroscopy.
New Chandra Results on Seyfert I Galaxies: Fe-K lines
Authors: Padmanabhan Urmila , Yaqoob Tahir
Published: July 2016

We present measurements of the Fe-Kα line for nine Seyfert I galaxies using Chandra High Energy Transmission Grating Spectrometer (HETGS) data. The centroid energies are narrowly dispersed (6.403 ± 0.062 keV) and indicate an origin of the line cores in cold matter. If all the lines in this sample were the peaks of a relativistically broadened disk line, it would require unrealistically fine tuning. However, at least three of the nine AGN clearly show a complex Fe-Kα line with an underlying broad component, possibly from a disk. In the others, an apparently narrow Fe-Kα line (even if it is resolved by Chandra) may still be due to the peak of a disk line. To distinguish this scenario from an origin in distant matter requires variability information.
Beaming Effect and Polarization of Blazars
Authors: Fan J. H.
Published: July 2016

Based on the beaming model, a relation between the observed polarization and Doppler factor was obtained for BL Lacertae objects–BLs by Fan et al. (1997). If flat spectral radio quasars—FSRQs fit a similar polarization-Doppler factor relation as BLs, then we can find that the ratio, f, of the de-beamed jet luminosity to the unbeamed luminosity in the source frame in BLs is greater than that in FSRQs. That difference in f is consistent with the result by Fan (2002a), which perhaps accounts for the emission line difference between BLs and FSRQs.
Some Recent Developments in γ-ray Burst Afterglow and Prompt Emission Models
Authors: Zhang Bing , Mészáros Peter , Wang Junfeng
Published: July 2016

Extensive observational campaigns of afterglow hunting have greatly enriched our understanding of the gamma-ray burst (GRB) phenomenon. Efforts have been made recently to explore some afterglow properties or signatures that will be tested by the on-going or the future observational campaigns yet come. These include the properties of GRB early afterglows in the temporal domain; the GeV-TeV afterglow signatures in the spectral domain; as well as a global view about the GRB universal structured jet configuration. These recent efforts are reviewed. Within the standard cosmological fireball model, the very model(s) responsible for the GRB prompt emission is (are) not identified. These models are critically reviewed and confronted with the current data.
Poynting Flux Dominated Black Hole-Accretion Disk System as GRB Power House
Authors: Lee Hyun Kyu , Kim Hui-Kyung
Published: July 2016

We investigate a black hole-accretion disk system which is dominated by Poynting flux to see whether it can be a possible power house for GRBs. For a set of GRBs for which the isotropic energy and Td are known, the effect of the disk mass and the magnetic field are discussed quantitatively using a simplified model. It is demonstrated explicitly that there is a lower limit on the angular momentum parameter for a given GRB energy. It is found that the most energetic GRBs can only accommodate relatively rapid-rotating black holes at the center.
Simple Reduction of Gamma-Ray Bursts
Authors: Liu Xiang
Published: July 2016

We try to explain the different type of GRBs from their properties, most likely the long duration GRBs are the NS-NS collision, short duration ones are the WD-WD collision, and intermediate ones are the NS-WD collision.
Possible Geometries for Afterglow of GRB990705
Authors: Wang X. Y. , Dai Z. G. , Lu T.
Published: July 2016

We investigate whether the circum-burst environment constrained by the absorption feature of GRB990705 could be consistent with the observed H-band afterglow. Two possible geometries of the afterglow-emitting regions are suggested: 1) afterglow emission produced by the impact of the fireball on the surrounding torus; 2)afterglow emission produced in the dense circum-burst medium inside the torus. In case 1), the faster decay at later time is attributed to the disappearance of the shock due to the counter-pressure in the hot torus illuminated by the burst and afterglow photons. For case 2), the circum-burst medium density is found to be very high (n ≳ 104 − 105cm−3).
Recent Status of High-Energy Gamma-Ray Astronomy
Authors: Takita Masato
Published: July 2016

Sub-TeV and TeV energy gamma-ray astronomy reveals non-thermal gamma-ray pictures of our universe and serve as a probe to understand the origin, acceleration and propagation of cosmic rays. Recent status of ground-based high-energy gamma-ray astronomy is reviewed.
Projected Rotational Velocities in Galactic OB Stars of Different OB Associations
Authors: Corral L. J. , Herrero A. , Villamariz M. R.
Published: July 2016

As a first step to study the influence that rotation has in the evolution of the most massive stars, we obtained the projected rotational velocity (v sin i) of a sample of OB stars from clusters and associations. We found that most of our stars present v sin i lower than 200 km/s.
Observational Effects of Corotating Interaction Regions in OB stars
Authors: Blomme R.
Published: July 2016

The stellar winds of OB stars are perturbed by Corotating Interaction Regions (CIRs). We present a 3D radiative transfer model which predicts that variations should occur in the infrared and millimetre continuum.
Evolutionary State of “Field” Be Stars Deduced from BCD Parameters
Authors: Zorec J. , Frémat Y. , Cidale L. , Hubert A. M. , Floquet M.
Published: July 2016

BCD (λ1, D) parameters of 49 “field” Be Stars are used to show that the Be phenomenon may appear over the whole main sequence evolutionary span. Models of rotating B stars are used to estimate the incidence of the fast rotation in the (λ1, D) parameters.
Co-rotating Circumstellar Clouds around Be Stars
Authors: Balona L. A.
Published: July 2016

A series of intensive high-resolution spectroscopic observations of 7 Be Stars conducted over 5 years strongly indicates that the source of mass loss in these stars is to be found in magnetic activity coupled with rapid rotation. Magnetic centrifugal acceleration of ionized H and He along open field lines produce the circumstellar disk, while gas trapped in closed magnetic loops are responsible for the periodic variations.
The Analysis of the Rotating Disk of some Southern Galactic B[e] Stars
Authors: Fernandes Marcelo Borges , Lamers H.J.G.L.M. , Kraus Michaela , de Araújo Francisco X.
Published: July 2016

The spectra of stars with the B[e] phenomenon are dominated by features that are related to physical conditions of circumstellar material around these objects and are not intrinsic to the stars. Previous studies have shown that emission lines present in the optical spectra of these objects are formed in an equatorial rotating disk. The analysis of high and low resolution spectra, obtained by us with 1.52 telescope in ESO for some Southern Galactic B[e] Stars, can give us information about the structure and velocity of the disk. We will describe the analysis of the unclassified B[e] star Hen 2-90.
A Rotational Period Study of a Large Sample of Pre-Main Sequence stars in NGC 2264
Authors: Lamm M. , Bailer-Jones C.A.L. , Mundt R. , Herbst W.
Published: July 2016

We present the results of a photometric monitoring program of pre-main sequence (PMS) stars in the young (2-4 Myr) open cluster NGC 2264 (d=700 pc). We find that the rotation periods are mass dependent and show a bimodal distribution for higher mass stars with M ≳ 0.3 M⊙ and a unimodal distribution for lower mass stars with M ≲ 0.3 M⊙.
Rotation of M and L Dwarfs from High Resolution Infrared Spectra
Authors: Hinkle Kenneth H. , Wallace Lloyd , Valenti Jeff , Tsuji Takashi
Published: July 2016

v sin i has been measured from high-resolution (λ/Δλ~50000) infrared spectra of ~30 M and L dwarfs. The spectral region observed covers approximately 0.01 μm centered at 2.312 μm in the CO 2-0 band. v sin i, measured from the CO lines, increases dramatically from the M to L dwarfs. In extreme cases the rotational periods are a few hours.
The Rotation of Red Giants and Horizontal Branch Stars
Authors: de Medeiros J. R.
Published: July 2016

Rotation is one of the most important observable in stellar astrophysics driving strongly the evolution of stars. This review presents the main observational results on the rotation of Red Giant and Horizontal-Branch stars carried out along the past 50 years. The review brings, in particular, the most recent results based on very accurate measurements of rotational velocity obtained mostly along the last decade.
Is there a Connection Between Non-Synchronous Rotation and X-Ray Emission in Massive Binary Systems?
Authors: Haro Sinhué , Juárez Juan Antonio , Koenigsberger Gloria
Published: July 2016

A correlation between orbital period and log(LX/Lbol) is found for a sample of B-type binary systems. We suggest that wind-wind collisions are the likely mechanism for generating the X-ray emission, and that the mass-loss rates may be enhanced in non-synchronously rotating systems due to the oscillations that are excited by the tidal forces.
Derivation of the Rotational Frequency of Massive Stars from Seismic Studies
Authors: Aerts C. , Scuflaire R. , Thoul A.
Published: July 2016

In this contribution we review the current status of the determination of the rotational frequency in non-radially pulsating B stars, i.e. β Cep stars and slowly pulsating B stars. Considerable progress is currently being made in the understanding of the non-radial oscillations of main-sequence B stars by means of high-temporal, high-spatial resolution spectroscopic time series. This has led to the detection of frequency multiplets, which are interpreted as rotationally splitted non-radial modes and which allow an accurate determination of the surface rotational frequency in some stars. We outline how our future goal, i.e. the derivation of the internal rotation frequency, can be achieved.
The Impact of Stellar Rotation on the Nitrogen Abundance Gradient from OB Stars in the Galactic Disk
Authors: Daflon Simone , Cunha Katia
Published: July 2016

Massive young stars can be used to trace the current chemical composition of the Galactic disk and to define its metallicity gradient. However, evolutionary models of massive rotating stars predict changes of the surface abundances due to rotationally induced mixing. The abundance analysis of elements sensitive to mixing, such as CNO, can be used to test these rotating stellar models. In this study we identify those stars that show one particular signature of mixing, N-enrichment, in our sample of 70 OB stars for which we have conducted an abundance analysis. This sample is used to define radial metallicity gradients in the Milky Way and we investigate the variation of the calculated nitrogen gradient after the exclusion of these, probably mixing-induced, N-rich stars.