bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of the Black-Hole Mass in 3C 273 by Multiband Observations
Authors: Ma Zhen Guo , Zhang Xi Zhen
Published: July 2016

With the determined black-hole (BH) spin of 3C 273 by data-fitting to the detected iron Kα line emission in the soft X-ray band, the BH mass of the galaxy is predicted by formulations of both the observed disk-luminosity in the optical-UV band and the observed jet-precession in the radio band. The multiband synthesis suggests that the BH is supermassive, 2.4 × 109M⊙. Simultaneously, other physical parameters are self-consistently obtained at the precessing radius of 230.2rg: the accretion rate of the disk is 74.9M⊙ yr−1, the Shakura-Sunyaev viscosity α is 0.134, and the radial & orbital velocities of fluid elements are 4.3 × 10−8 and 6.6 × 10−2, respectively.
A Model for the Molecular Maser Disk in NGC4258
Authors: Babkovskaia Natalia , Poutanen Juri
Published: July 2016

A model of the H2O maser disk observed in the nucleus of the galaxy NGC4258 is presented. The hot-gas–cold-dust pumping mechanism based on the difference between gas and dust temperatures and special features of the ice spectrum is used. Conditions for the maser level inversion are calculated in the case of unsaturated maser. It is shown based on the observational data that the maser in NGC 4258 seems to be unsaturated. In that case the spectrum of the maser radiation at λ = 1.35 cm including the central and high velocity components is calculated. The key parameters of the molecular maser disk are determined by comparing results of numerical simulations with the data.
The X-ray Spectral Properties for Gamma-ray Loud Blazars
Authors: Dai Ben-Zhong
Published: July 2016

We selected a sample of bright γ-ray (E>100 MeV) blazars whose X-rays in 0.1–10.0 keV band are observed by ROSAT and other X-ray satellites, and make a detailed spectral analysis between the soft (0.1–2.0 keV) and hard band (2.0–10.0keV) as well as between X-ray and γ-ray properties using both un-weighted and weighted analysis methods. Our results indicate: (i) there are significant anti-correlations of the spectral indices between soft X-rays and γ-rays, and between hard X-ray and γ-ray of flat-spectrum radio quasars (FSRQs) and BL Lac objects; (ii) in the X-ray band, the correlation is confusing, there is positive correlation of the spectral indices between soft and hard X-ray band using weighted correlation analysis, but this correlation is negative using un-weighted correlation analysis.
Discovery of Helical Magnetic Fields in AGN, and CME and Ejection of Large-Scale Magnetic Fields from AGN
Authors: Chu Han-Shu , Baath L. B. , Zhang Fu-Jun , Spencer R. E.
Published: July 2016

Magnetic Fields are the crucial and most important ingredient involved in the processes of various violent activities in Active Galactic Nuclei and other celestial bodies. The generally accepted 2-sided symmetric-jets model of active galactic nuclei (AGN) does not include the magnetic fields. We present here the first direct detection of helical magnetic field in AGN, and the first direct detection of ejection of large scale magnetic fields from AGN. (CME) 2. The annular (helical) magnetic field is responsible for the collimation of the jet (through Pinch Effect) and may be of crucial importance for extraction of black hole rotational energy. 3. The CMEs are responsible for sporadic ejection of jet components in AGN, while the general accepted 2-sided jets pertain to the quiescent Jets. 4. Observations show that the CME with Asymmetric Jets can explain many phenomena and much of the morphological diversities in AGN.
Gamma-ray Burst Spectrum Influenced by the Doppler Effect of Fireballs
Authors: Qin Yi-Ping
Published: July 2016

The formula of the Doppler effect of fireballs, which shows how the observational flux from fireballs would be expected, is presented. It shows, when the expansion speed is very large, a weak radiation at X-ray bands would be significantly enhanced to detectable levels and shifted to much higher bands to become a gamma-ray source; at the same time, the peak of the spectrum would shift to a much higher energy band as well.
Towards Teraton EeV Neutrino Telescopes
Authors: Gorham Peter W.
Published: July 2016

The highest energy cosmic rays provide compelling evidence for EeV neutrino sources, if we can achieve the Teraton target volumes needed. At 10 TeV energies and above neutrino astronomy is in fact the only astronomy with a clear view of the whole universe. Radio detection of neutrino cascade interactions in ice and other solid dielectric media, via the Askaryan effect, provide a realistic path toward this goal.
Advantages of the Broadening Function (BF) over the Cross-Correlation Function (CCF)
Authors: Rucinski Slavek M.
Published: July 2016

Performance of the cross-correlation function (CCF) is compared with the linear, algebraic equations, least-squares deconvolution directly giving the broadening function (BF). The many disadvantages of the CCF do not outweigh its simplicity so that the BF approach is strongly advocated.
Rotation and Line Broadening in OBA Stars
Authors: Howarth Ian D.
Published: July 2016

Observational v sin i line-width measurements for OBA stars are summarized, and the relationship of these measurements to ve sin i, the true projected equatorial rotation velocity, reviewed. In general, ve sin i ≥ v sin i for Be Stars, while ve sin i ≤ v sin i for O-type stars. The implications are that (i) it is probable that Be Stars are closer to their critical rotation velocities than is generally supposed (rendering plausible a range of new physical mechanisms for the Be phenomenon); and (ii) some non-rotational macroscopic line broadening (‘turbulence’) occurs in the atmospheres of O stars (and BA supergiants). Physical interpretations of this ‘turbulence’ are considered.
The Possibility of a Disk Formation around Late B Stars
Authors: Kubát Jiří , Krtička Jiří , Pustylnik Izold B. , Votruba Viktor
Published: July 2016

Line driven wind in late B stars causes significant heating of layers just above the photosphere. This large heating is a source of a thermal wind, which together with fast rotation opens the possibility of a formation of a disk. We refer to such disk as to a radiation induced disk. Disk inhibition by nonradial line force has only little effect in this case, since absorption in spectral lines is not the main wind driving mechanism.
Rotational Velocities of B, A, and Early-F Stars
Authors: Fekel Francis C. , Warner Phillip B. , Kaye Anthony B.
Published: July 2016

Projected rotational velocities for 67 B, A, and early-F stars have been determined. Some of these stars are early-type, radial-velocity standard candidates. The spectra of seven stars show metallic lines with composite profiles that consist of a narrow component near the center of a broad component, suggesting that they may be shell stars or binaries.
Stellar Rotation in the Young Cluster M17
Authors: Huang Wenjin , Gies Douglas , Massey Philip , Conti Peter S.
Published: July 2016

We constructed line profile models for young OB stars in M17 using TLUSTY and SYNSPEC, including the effects of rotational flattening and gravitational darkening. The values of v sin i for 8 member stars (with spectral classifications O4.5 V to O9 V) range from 7 km s–1 to 168 km s–1. The mean value of v sin i (102 km s–1) is lower than expected for very young clusters.
How Frequent is Evolutionary Spin-Up in Binary Be Stars?
Authors: Maintz M. , Rivinius Th. , Štefl S. , Stahl O.
Published: July 2016

Satellite absorptions are identified as a general feature of Be binaries. In addition, Be + sdO binaries seem to show a characteristic short-term emission variability and short-lived shell events. The identification of such features can ease the search for further Be binaries with hot companions to allow an estimate of the fraction of Be Stars, possibly spun-up through binary evolution.
Rotation of B[e] Supergiants, Luminous Blue Variables and Wolf-Rayet Stars
Authors: Eenens Philippe
Published: July 2016

A brief review of the observational properties of evolved massive stars is presented. In the pursuit of clues for their rotation, formidable difficulties are encountered. At the same time, common features emerge between B[e] supergiants, Luminous Blue Variables and Wolf-Rayet stars. Several indications of rapid rotation are found, mostly indirect ones, in each class. It is shown that fast rotation can probably survive the mass loss events which characterize the late evolution of massive stars.
The Erupting Star in HD5980: A Rapid Rotator?
Authors: Georgiev Leonid , Koenigsberger Gloria
Published: July 2016

We present evidence suggesting that the star that erupted in 1994 in the SMC multiple system HD 5980 has v sin i ~230 km s–1, which is close to the breakup velocity for this star.
The Rotation of Low-Mass Pre-Main-Sequence Stars
Authors: Mathieu Robert D.
Published: July 2016

Major photometric monitoring campaigns of star-forming regions in the past decade have provided rich rotation period distributions of pre-main-sequence stars. The rotation periods span more than an order of magnitude in period, with most falling between 1 and 10 days. Thus the broad rotation period distributions found in 100 Myr clusters are already established by an age of 1 Myr. The most rapidly rotating stars are within a factor of 2-3 of their critical velocities; if angular momentum is conserved as they evolve to the ZAMS, these stars may come to exceed their critical velocities. Extensive efforts have been made to find connections between stellar rotation and the presence of protostellar disks; at best only a weak correlation has been found in the largest samples. Magnetic disk-locking is a theoretically attractive mechanism for angular momentum evolution of young stars, but the links between theoretical predictions and observational evidence remain ambiguous. Detailed observational and theoretical studies of the magnetospheric environments will provide better insight into the processes of pre-main-sequence stellar angular momentum evolution.
On the Relationship Between Stellar Rotation and Radius in Young Clusters
Authors: Rebull L. M. , Wolff S. C. , Strom S. E. , Makidon R. B.
Published: July 2016

We have compiled data from the literature on rotational velocities and/or periods for > 1000 K & M stars in 10 young clusters ranging in age from Orion to the IC 1391/2602. These data show that most PMS stars < 3 Myr do not appear to spin up in response to contraction, but there is a suggestion of slight spinup by ~8 Myr. These results extend and reinforce our earlier study (Rebull et al. 2002), based on observations of ~300 stars in the Orion Flanking Fields, NGC 2264, and the Orion Nebula Cluster (ONC), which showed that the majority of PMS stars in these three groups apparently do not conserve stellar angular momentum as they contract, but instead evolve at nearly constant angular velocity. This result applies both to stars with and without near-IR I – K excesses indicative of disks.
Observations of Rotation in Binary Stars
Authors: Koenigsberger Gloria
Published: July 2016

A brief overview of the available information of v sin i and stellar radii in binares is presented.
A 10-Day Binary System Orbiting the Be Star 66 Oph
Authors: Štefl S. , Hadrava P. , Baade D. , Rivinius Th. , Maintz M. , Stahl O.
Published: July 2016

66 Oph is a multiple system with a close binary orbiting the B2Ve primary Be star. The binary parameters were derived by two independent methods and spectra of components BA and BB were separated by Fourier disentangling.
Rotation and Magnetic Activity in Brown Dwarfs
Authors: Basri Gibor
Published: July 2016

Brown dwarfs and very low mass (VLM) stars are the last frontier on the map of the angular momentum histories of star-like objects. Until the advent of 8-m class telescopes, it was impossible to obtain spectra with enough resolution to detect their rotation. The very existence of brown dwarfs was only established then. It was immediately apparent that there are differences between VLM objects and their heftier stellar cousins. Field VLM objects were found to be very rapidly rotating, yet they did not display the strong magnetic activity that would be expected of convective objects in that case. We now have a good preliminary understanding of the situation near the substellar boundary. I summarize the rotational data (both spectroscopic and photometric) on VLM objects, and how rotation and temperature fit into the production of magnetic activty. I also report more recent work on VLM objects when they are very young. There is increasing evidence that they form much like stars, beginning (when they become visible) as relatively slow rotators for the most part, followed by spin-up as they contract. Their disk lifetimes may be shorter, and they are more magnetically active when they are young. The subsequent angular momentum history of VLM objects is different from solar-type stars, as the usual magnetic braking mechanisms do not operate as in the stellar case. Much of the new work reported here is from the thesis of Subanjoy Mohanty, and was supported by NSF/AST-0098468.
Dynamical Processes Induced by the Internal Solar Rotation
Authors: Turck-Chièze S.
Published: July 2016

Helioseismology has been developed to extract internal sound speed, rotation and magnetic field. Such informations will put strong constraints on the present missing dynamical phenomena. Starting from the present observations on the rotation, I discuss quantitatively two important regions, the transition region between radiation and convection, called tachocline and the radiative region. In the tachocline, lithium indicator shows that a turbulent mixing is certainly present in main sequence solar like stars. on the other end, a detailed study of pre-main sequence stars encourages also the introduction of magnetic effects in addition to such a term below 10 Myr. For the solar radiative zone, the difficulty to determine the rotation profile is first noticed and discussed showing the great advantage of the gravity modes or mixed modes in addition to the acoustic modes. A possible profile, decreasing from 0.4 to 0.2 R⊙ and then increasing in the very central region is suggested by the present observations. The consequences in terms of dynamical processes are discussed.
The Small-Péclet-Number Approximation for Radiative Zones and its Application to Shear Layer Instabilities
Authors: Lignières F.
Published: July 2016

Thermal diffusivities within stars are higher by several orders of magnitude than in the earth atmosphere. This particularity of the stellar fluid has subtle effects on the dynamics of stably stratified radiative zones as it contributes to favour some flows and supress others. An asymptotic analysis of hydrodynamic equations for large values of the thermal diffusivity is presented and this results in a simplification of the dynamical effects of the thermal diffusivity. This asymptotic behavior proved to be very useful to understand shear instabilities of Kelvin-Helmholtz type.
Three Single Stars (See How They Spin)
Authors: Charbonneau Paul
Published: July 2016

I describe three key moments in the rotational evolution of three single stars, chosen to illustrate the richness and complexity of the interaction between rotation and magnetic fields. I then piece together two general scenarii for the rotational evolution of early-type and late-type stars, in which the “fossil” magnetic field inherited by a star from its formative years basically sets its subsequent rotational fate. Since no one has yet offered a convincing scenario according to which a star could somehow get rid of its primordial fossil field, the inescapable conclusion is that magnetic fields cannot be neglected in modelling rotation, and that “rotational evolution” should really be thought of as “magnetorotational evolution”.
Looking Deep Within an A-type Star: Core Convection Under the Influence of Rotation
Authors: Brun Allan Sacha , Browning Matthew , Toomre Juri
Published: July 2016

The advent of massively parallel supercomputing has begun to permit explicit 3–D simulations of turbulent convection occurring within the cores of early-type main sequence stars. Such studies should complement the stellar structure and evolution efforts that have so far largely employed 1–D nonlocal mixing length descriptions for the transport, mixing and overshooting achieved by core convection. We have turned to A-type stars as representative of many of the dynamical challenges raised by core convection within rotating stars. The differential rotation and meridional circulations achieved deep within the star by the convection, the likelihood of sustained magnetic dynamo action there, and the bringing of fresh fuel into the core by overshooting motions, thereby influencing main sequence lifetimes, all constitute interesting dynamical questions that require detailed modelling of global-scale convection. Using our anelastic spherical harmonic (ASH) code tested on the solar differential rotation problem, we have conducted a series of 3–D spherical domain simulations that deal with a simplified description of the central regions of rotating A-type stars, i.e a convectively unstable core is surrounded by a stable radiative envelope. A sequence of 3–D simulations are used to assess the properties of the convection (its global patterns, differential rotation, meridional circulations, extent and latitudinal variation of the overshooting) as transitions are made between laminar and turbulent states by changing the effective diffusivities, rotation rates, and subadiabaticity of the radiative exterior. We report on the properties deduced from these models for both the extent of penetration and the profile of rotation sustained by the convection.
Rotating Models for Evolved Low-Mass Stars
Authors: Charbonnel Corinne , Palacios Ana
Published: July 2016

Low mass stars (< 2-2.5 M⊙) exhibit, at all the stages of their evolution, signatures of processes that require challenging modeling beyond the standard stellar theory. In this paper we focus on their peculiarities while they climb the red giant branch (RGB). We first compare the classical predictions for abundance variations due to the first dredge-up with observational data in various environments. We show how clear spectroscopic diagnostics probe the nucleosynthesis and the internal mixing mechanisms that drive RGB stars. Coherent data reveal in particular the existence of a non-standard mixing process that changes their surface abundances at the so-called RGB bump. By reviewing the models presented so far to explain the various abundance anomalies, we show that the occurrence of this extra-mixing process is certainly related to rotation. Finally we discuss the so-called Li-flash which is expected to occur at the very beginning of the extra-mixing episode.
Rotation and Mass Ejection: the Launching of Be-Star Disks
Authors: Owocki Stanley P.
Published: July 2016

The characteristic signature of Be Stars is the Balmer line emission understood to arise in a circumstellar disk. Unlike the accretion disks of protostars or mass-exchange binary systems, the evolved and generally single or wide-binary status of Be Stars seems to require that its disk must form from mass ejection (a.k.a. decretion) from the star itself. In this paper, I use analogies with launching orbital satellites to discuss two candidate processes (radiation, pulsation) for driving such orbital mass ejection, with particular emphasis on the role of the rapid, possibly near-critical, rotation of Be Stars in facilitating the formation of their signature disks.
Inhibition of Wind-Compressed Disk Inhibition in Optically Thick Winds
Authors: Gayley K. G.
Published: July 2016

There are three important effects in optically thin line-driven winds that have been shown to inhibit the equatorial compression inherent in the wind-compressed disk model:

1) gravity darkening, which concentrates the driving flux over the poles,

2) stellar oblateness, which rotates the flux vectors poleward, and

3) nonisotropic opacity, which rotates the force vectors poleward.

The first two of these effects tend to yield fairly spherical winds, while the last one actually reverses the wind compression and should generate prolate winds. This poster argues that this third mechanism is not present for multiline scattering in Wolf-Rayet winds. Hence, it is argued that rotating optically thick line-driven winds should have a more spherical UV photosphere, especially for CAK α ≅ 2/3. However, owing to flux migration from polar to equatorial regions, such winds should have an even more prolate optical photosphere.
The Effects of Stellar Yields with Rotation on Chemical Evolution Models
Authors: Carigi Leticia , Pettini Max
Published: July 2016

We summarise the results of recent work investigating the effects of stellar yields which take into account rotation on the predictions of chemical evolution models for early populations of galaxies.
Intergalactic HI Clouds
Authors: Briggs F. H.
Published: July 2016

Neutral intergalactic clouds are so greatly out numbered by galaxies that their integral HI content is negligible in comparison to that contained in optically luminous galaxies. In fact, no HI cloud that is not associated with a galaxy or grouping of galaxies has yet been identified. This points to a causal relationship that relies on gravitational potentials that bind galaxies also being responsible for confining HI clouds to sufficient density that they can become self-shielding to the ionizing background radiation. Unconfined clouds of low density become ionized, but confined clouds find themselves vulnerable to instability and collapse, leading to star formation.
HI Observations of Nearby Dwarf Galaxies
Authors: Bouchard Antoine , Carignan Claude , Staveley-Smith Lister , Jerjen Helmut , Freeman Ken
Published: July 2016

We present HI detections towards several Local Group dSphs and dIrr/dSphs. The possibility that the detected emission can be due to High Velocity Clouds (HVC) is ruled out although it appears that most of our targets are in HVC rich regions.
The Properties of Radio Selected Galaxies in HIPASS/HIJASS and SDSS
Authors: Garcia-Appadoo Diego A. , Kilborn Virginia A. , West Andrew A. , Dalcanton Julianne J. , Disney Mike J.
Published: July 2016

We present a preliminary analysis of the properties of HI selected galaxies selected from the HIPASS and HIJASS surveys and that fall within the SDSS. Prom SDSS photometry in the early data release (EDR), we have obtained optical properties such as color, morphology, surface brightness and size. By comparing these with the HI properties derived from HIPASS/HIJASS, we are able to find relationships between the cool gas and the current generation of stars.
Intracluster Planetary Nebulae in Clusters and Groups
Authors: Feldmeier John J. , Ciardullo Robin B. , Jacoby George H. , Durrell Patrick R. , Mihos J. Christopher
Published: July 2016

We present the results from multiple surveys for intracluster planetary nebulae (IPNe) in nearby galaxy clusters and groups. We find that in the case of clusters, our observations imply: 1) the amount of intracluster starlight is significant, up to 20% of the total starlight, 2) in Virgo, is elongated along our line of sight, and 3) is clustered on the sky, implying ongoing tidal stripping. In contrast, searches for IPNe in groups have found little or no intra-group population, implying there may be something in the cluster environment that significantly enhances intracluster star production. from high-resolution N-body simulations, we find that the IPNe should create observable features in position-velocity space, and that these features may eventually allow us to place limits on the dynamics of galaxy clusters.
The Orientation of Galaxies in Nearby Galaxy Groups
Authors: Flin P. , Biernacka M. , Krywult J.
Published: July 2016

The statistical analysis of six nearby groups of galaxies, connected with the Milky Way, M31, M81, M101, NGC5128 and NGC5236 shows an isotropic distribution of galaxy planes, similarly to galaxies within the Local Group. Also planes of galaxies in the nearby (Vr < 500 km s−1) region of the Local Supercluster exhibit random distribution, disregarding their membership to groups. The result shows that strong environmental effects observed among dwarf galaxies do not change generally random distribution of galaxy planes in this region.
A Model of Gas Recycling Based on Condensed H2
Authors: Pfenniger Daniel
Published: July 2016

To address, among other questions, puzzling observations about star forming in the extreme outer HI disk of M31 (Cuillandre et al. 2001), a scenario of interstellar gas cycling between the visible and a very cold invisible phase is investigated. The key new element sketched here, allowing to maintain the bulk of the gas out of sight, is that molecular hydrogen becomes liquid or solid below 33 K at sufficiently high pressure, allowing AU-sized spheres of very cold gas to be stabilised by incompressible cores of condensed H2 (Pfenniger 2004). These predicted cold gas globules are relatively weakly bound (~ 10−3eV/nucleon), such that their lifetime depends directly on the ambient UV/CR excitation level. At galactic scale the globules behave as collisionless bodies, and evaporate and become the usual visible ISM gas through heating. Much of the ISM gas can thus spend a long time in this cold condensed phase in low excitation regions. N-body simulations of galactic disks modeling such effects have been run, and some of their features are described in more detail in this volume and elsewhere (Revaz & Pfenniger 2004).
Galactic Metallicity Distribution from Open Clusters
Authors: Chen L. , Hou J. L. , Wang J. J.
Published: July 2016

We have compiled two new Galactic open cluster catalogues. The first one has 119 objects with age, distance and metallicity data, while the second one has 144 objects with both absolute proper motion and radial velocity data, of which 45 clusters also with metallicity data available. An iron radial gradient of about −0.063±0.008 dex kpc−1 is obtained from our sample. By dividing clusters into age groups, we show that iron gradient was steeper in the past. A disk age-metallicity relation could very probably exist based on the current sample.
The Iron Abundance in Blue Compact Galaxies
Authors: Rodríguez M. , Esteban C.
Published: July 2016

We determine the Fe abundances for several blue compact and emission-line galaxies. The O/Fe abundance ratios are found to increase with the metallicity of the galaxy, and to decrease with its degree of ionization. These correlations are interpreted as reflecting a decrease for lower metallicities of the depletion of Fe atoms on to dust grains, probably arising from the harder radiation fields prevailing at low metallicities.
XMM-Newton Observations of Hot Gas in Low Mass Dwarf Galaxies
Authors: Walter Fabian , Kerp Jürgen , Kappes Meikel
Published: July 2016

We present first results of our XMM-Newton study of the nearby dwarf galaxies IC 2574, Holmberg I and Sextans A. Soft X-ray emission has been detected in IC 2574 and X-ray point sources (presumably X-ray binaries) are detected in all three galaxies.
3D Studies of Recycling Signatures within Irregular Galaxies
Authors: Valdez-Gutiérrez Margarita , Rosado Margarita
Published: July 2016

We present a 3D analysis based on Fabry-Perot data of some astronomical objects directly related to recycling processes within the irregular galaxies NGC4449 and IC1613.
A Reference Sample: ISM of the Most Isolated Galaxies
Authors: Verdes-Montenegro L. , Sulentic J. , Espada D. , Leon S. , Lisenfeld U. , Verley S. , Huchtmeier W. , Odewahn S. , Garcia E. , Yun M. S. , del Río S. , Combes F.
Published: July 2016

We are constructing the first complete unbiased control sample of the most isolated galaxies of the northern sky to serve as a template in the study of star formation and galaxy evolution in denser environments. Our goal is to compare and quantify the properties of different phases of the interstellar medium in this sample, as well as the level of star formation, both relevant parameters in the internal evolution of galaxies and strongly conditioned by the environment. To achieve this goal we are building a multiwavelength database for this sample to compare and quantify the properties of different phases of the ISM.
Simulations on the Collisional Properties of Gas in Galaxies
Authors: Revaz Yves , Pfenniger Daniel
Published: July 2016

In this work, we explore a simple method with few free parameters, which describes the global dynamical consequences on disk galaxies of a slow cycling of gas between the interstellar, almost collisionless very cold gas and the warm collisional phases, with a secular transformation of a fraction of warm gas into stars.
The Metal Absorption Systems of the FDF QSO 0103-260
Authors: Appenzeller Immo , Noll Stefan , Stahl Otmar , Frank Stephan
Published: July 2016

Using the UVES echelle spectrograph at the ESO VLT we obtained high-resolution (R=40 000) spectra of the QSO 0103-260 in the FORS Deep Field (FDF). In addition to numerous Ly forest lines we identified 16 metal absorption systems with redshifts between 0.97 < z < 3.36. A comparison of the observed redshift distributions of the metal line systems and of the spectroscopically observed galaxies in the FDF shows that the distribution of metal absorption clouds and of the galaxies along the line of sight to the QSO are well correlated and obviously trace the cosmic structure in the direction of the FDF.
A Galactic Example of a Massive Chimney
Authors: McClure-Griffiths N. M. , Dickey J. M. , Gaensler B. M. , Green A. J.
Published: July 2016

One mechanism for spreading hot, metal enriched gas away from galaxies is through gigantic chimneys formed in the disk of a galaxy. Chimneys form when shells or bubbles blown by many massive stellar winds and supernova explosions grow large enough to exceed the neutral hydrogen (H I) scale height of the disk. The shells then become unstable at their polar regions and expand rapidly, breaking out to the galaxy's halo. If galactic fountain models are correct the hot gas liberated by these chimneys should cool into H I cloudlets high above the galaxy's disk. The Milky Way provides the nearest laboratory to search for these objects in order to study how they form and the fate of the expelled gas. While we expect tens of chimneys in the Milky Way to account for the thermal support of the halo there are only a few known chimneys. Here we present an H I study of one Galactic chimney GSH 277+00+36. GSH 277+00+36 is the the only chimney known to have blown out of both sides of a galactic disk. We discuss the development of Rayleigh-Taylor instabilities in this object and the role those may have had in the formation of the chimney.
Superwind Galaxies at High Redshift: the Case of LAE J1044-0130
Authors: Ajiki Masaru , Fujita Shinobu S. , Shioya Yasuhiro , Nagao Tohru , Murayama Takashi , Taniguchi Yoshiaki
Published: July 2016

Superwind galaxies at high-redshift are now considered to be the important clue for understanding the interaction and evolution of both galaxies and intergalactic matter. In order to improve our knowledge of superwind galaxies at high redshift, a large sample of superwind candidates is needed. During the course of our new search for Lyman alpha emitters at z = 5.7, we have found a candidate superwind galaxy, LAE J1044-0130, at z = 5.69. The emission-line profile of this object is asymmetric, showing excess red-wing emission and the observed broad line width (= 340 km/s). In this poster, we report detailed observed properties of LAE J1044-0130 as an example of a superwind galaxy.
High Resolution Observations of Molecular Gas in the Outflow of M 82
Authors: Walter Fabian , Weiss Axel , Scoville Nick
Published: July 2016

We present a high-resolution (3.6“, 70 pc) CO(1-0) mosaic of the molecular gas in M 82 covering an area of 2.5'x3.5’ (2.8 kpc x 3.9 kpc) obtained with the OVRO millimeter interferometer. The observations reveal the presence of huge amounts of molecular gas (> 70% of the total molecular mass, Mtot ≈ 1.3 × 109M⊙) outside the central 1 kpc disk. Molecular streamers are detected in and below M 82's disk out to distances from the center of ~1.7 kpc. Some of these streamers are well correlated with optical absorption features; they form the basis of some of the prominent tidal HI features around M 82. This provides evidence that the molecular gas within M 82's optical disk is disrupted by the interaction with M 81. Molecular gas is found in M 82's outflow/halo, reaching distances up to 1.2 kpc below the plane; CO line-splitting has been detected for the first time in the outflow. The maximum outflow velocity is ~ 230 km s−1; we derive an opening angle of ~ 55° for the molecular outflow cone. The total amount of gas in the outflow is > 3 × 108 M⊙ and its kinetic energy is of order 1055 erg, about one percent of the estimated total mechanical energy input of M 82's starburst. Our study implies that extreme starburst environments can move significant amounts of molecular gas in to a galaxy's halo (and even to the intergalactic medium).
Cluster Formation with Chemical and Energy Feedback
Authors: Portinari L. , Sommer-Larsen J. , Romeo A. D.
Published: July 2016

We present fully cosmological, hydrodynamical simulations of clusters of galaxies, including star formation, supernova feedback, chemical enrichment and metal-dependent cooling. We investigate the relation between feedback, metal enrichment of the intra-cluster medium (ICM) and the distribution of baryons in the various phases (cold gas+stars and hot ICM) at varying Initial Mass Function and wind efficiency.
Subaru Spectroscopy of the Giant Lyα Nebula around 1243+036
Authors: Ohyama Youichi , Taniguchi Yoshiaki
Published: July 2016

We present our new spatially-resolved, optical spectroscopy of the giant Lyα nebula around the powerful radio galaxy 1243+036 (=4C+03.24) at z = 3.57. The nebula is extended over ~ 30 kpc from the nucleus, and forms a pair of cones or elongated bubbles. The high-velocity (~ −1000 km s−1; blueshifted with respect to the systemic velocity) Lyα-emitting components are detected at both sides of the nucleus along its major axis. We discuss possible origin of the nebula; 1) the shock-heated expanding bubble or outflowing cone associated with the superwind activity of the host galaxy, 2) halo gas photoionized by the anisotropic radiation from the active galactic nuclei (AGN) and 3) the jet-induced star-formation or shock. The last possibility may not be likely because Lyα emission is distributed out of the narrow channel of the radio jet. We show that the superwind model is most plausible since it can explain both the characteristics of the morphology (size and shape) and the kinematical structures (velocity shift and line width) of the nebula although the photoionization by AGN may contribute to the excitation to some extent.
Deep Spectroscopy of the Very Extended Ionized Gas of NGC 4388
Authors: Yoshida Michitoshi , Yagi M. , Okamura S. , Ohyama Y. , Kashikawa N. , Sasaki T. , Aoki K. , Iya M.
Published: July 2016

We report here the results of deep optical spectroscopy of the very extended emission-line region (VEELR) found serendipitously around the Seyfert 2 galaxy NGC 4388 in the Virgo cluster. The Hα recession velocities of most of the filaments of the region observed are highly blue-shifted with respect to the systemic velocity of the galaxy. The velocity field is complicated, and there seem to be several streams of filaments ranging from ~ −100 km s−1 to ~ −700 km s−1 with respect to the systemic velocity of the galaxy. The emission-line ratios of the VEELR filaments are well explained by power-law photoionization models with solar abundances. In addition to photoionization, shock heating probably contributes to the ionization of the gas. We conclude that the VEELR was formerly the disk gas of NGC 4388, which has been stripped by ram pressure due to the interaction between the hot intra-cluster medium (ICM) and the galaxy.
Head-on collisions: how to bring large quantities of gas out of inner disks
Authors: Braine Jonathan , Lisenfeld U. , Duc P.-A.
Published: July 2016

Head-on collisions of spiral galaxies can bring large quantities of gas out of spiral disks and into the intergalactic medium. Only two clear cases (UGC 12914/5 and UGC 813/6) of such collisions are known (Condon et al. 1993, 2002) and in both cases several 109 M⊙ of neutral gas is found in the bridge between the two galaxies which are now separating. About half of the gas is molecular. The gas, atomic or molecular, is brought out by collisions between clouds, which then acquire an intermediate velocity and end up between the galaxies. The bridges contain no old stars and in each case only one HII region despite the large masses of molecular gas, such that the star formation efficiency is very low in the bridges. The collisions occurred 20 – 50 million years ago, much greater than the collapse time for dense cores. We (Braine et al. 2003, 2004) show that collisions between molecular clouds, and not only between atomic gas clouds, bring gas into the bridges. It is not currently known whether the galaxies and bridges are bound or whether they will continue to separate, releasing several 109 M⊙ of neutral gas into the intergalactic medium.
A Structural NIR Analysis of the Interacting Pair of Galaxies KPG 404 (NGC 5394/95)
Authors: Valdez-Gutiérrez Margarita , Puerari Ivânio , Hernández-López Izbeth
Published: July 2016

We present near infrared observations in J, H and K' pass-bands of the interacting pair of galaxies KPG 404 (NGC 5394/95). We calculate total magnitudes, surface brightnesses and colour profiles. We present the growth curve to compare our photometry against earlier works in which circular aperture estimations were published. We also perform a structural (disk + bulge) analysis to get insight on the morphology of the pair. The disk+bulge fit shows that NGC 5394 (KPG 404A) is more compact than normal galaxies, while NGC 5395 (KPG 404B) is less concentrated. This suggests an interacting scenario in which NGC 5394 passes through the disk of NGC 5395 (a Cartwheel-type collision), rather than a passage as M51-type pairs.
Magnetic Fields in Strongly Interacting Galaxy Systems
Authors: Chyży Krzysztof T. , Beck Rainer
Published: July 2016

We obtained VLA radio total power and polarization maps of a merging pair of galaxies NGC4038/39. The whole system is filled with bright extended radio emission with a high thermal fraction of ⋍ 50% at 10.45 GHz and very strong magnetic fields of ⋍ 20μG. A star-forming region at the southern end of the dark cloud complex extending between the galaxies has highly tangled magnetic fields reaching the strength of ⋍ 30μG, even larger than in both individual galaxies. The polarized components associated with the HI ridge at the base of one of the tidal tails and with the northern complex of dark clouds (weakly forming stars) have been identified. A relic magnetic spiral coincident with the northern galaxy has been found, too. Our data on the magnetic fields combined with those in HI, Hα, X-rays and in far infrared are used as a diagnostic tool to distinguish several physically distinct regions.
Efficiency of Stripping Mechanisms
Authors: Combes Françoise
Published: July 2016

There are several physical processes to remove gas from galaxies in clusters, with subsequent starvation and star formation quenching: tidal interactions between galaxies, or tidal stripping from the cluster potential itself, interactions with the hot intra-cluster medium (ICM) through ram pressure, turbulent or viscous stripping, or also outflows from star formation of nuclear activity, We review the observational evidence for all processes, and numerical simulations of galaxies in clusters which support the respective mechanisms. This allows to compare their relative efficiencies, all along cluster formation.
A new 4m millimeter-wave telescope for a southern sky CO survey
Authors: Fukui Y. , Ogawa H. , Kawabata K. , Mizuno A. , Sugitani K.
Published: July 2016

We plan to install a new 4m radiotelescope in Australia to complete a sky survey of star-forming regions in the millimeter-wave CO(J=1-0, J-2-1) emission.
The evolution of AGB stars in the Magellanic Clouds
Authors: Westerlund B.E. , Azzopardi M. , Breysacher J. , Rebeirot E.
Published: July 2016

Photoelectric observations of over 100 C stars in the Small Magellanic Cloud (SMC) and 20 in the Large Magellanic Cloud (LMC) were carried out with the Johnson JHK system using the standard ESO equipment on the 3.6m telescope. The limiting magnitude is about K = 13.7.
Recent star formation history in the region of 30 Doradus
Authors: Lortet M. -C. , Testor G. , Martin N.
Published: July 2016

The main purpose of our work is to study the range of ages of the stars in an area about 40' in diameter around R 136. Apart from individual stellar spectra, other age criteria may be found in photometric studies, the morphology and the density of the associated gas. In such complex regions as the 30 Dor region, estimating the depth along the line of sight is a problem.
The dynamics of NGC 1866
Authors: Fischer Phil , Welch D.L. , Cote P. , Mateo M. , Madore Barry F.
Published: July 2016

High-precision radial velocity measurements have been obtained for 62 stars in the young LMC cluster NGC 1866 using the Las Campanas 2.5m with échelle spectrograph. The mass-weighted mean-square velocity dispersion is σ2 = 6.5 ± 1.3 km2 s−2. The mass of the cluster M(r < 20) = 8.1 ± 1.6 × 104M⊙, implying a M/L of 0.20 ± 0.04 in solar units.
The interstellar reddening and metallicity of NGC 330
Authors: Bessell Michael S.
Published: July 2016

A reddening of E(B-V) = 0.12 ± 0.02 has been determined for NGC 330 in the Small Magellanic Cloud (SMC) from spectrophotometry of B stars in the cluster. This high reddening helps explain many of the anomalous low metallicity estimates for the cluster. Preliminary analysis of Coudé spectra of K giants in the cluster indicates a high value of 3.5 to 4.5 km s−1 for the micro-turbulence, and a metallicity near −0.7 dex with respect to the sun.
IUE observations of stars in NGC 330 in the Small Magellanic Cloud
Authors: Caloi V. , Cassatella A. , Castellani V. , Klare G.
Published: July 2016

Low resolution spectra from 1200 to 3300Å have been obtained, with the IUE satellite, for seven blue giants and supergiants in the young, metal-poor globular cluster NGC 330 in the Small Magellanic Cloud (SMC). A further three spectra from the IUE archive have been added to the sample, covering a range of 2.5 mag. The effective temperatures and the local reddening in the SMC have been estimated, and the star positions in the theoretical HR diagram determined, and compared with theoretical predictions for massive star evolution. Substantial discrepancies have been found.
First CCD observations of Magellanic Cloud variable stars from the Mt John University Observatory, New Zealand
Authors: Tobin William , Gilmore A. C. , Wadsworth Alan , West S.R.D.
Published: July 2016

Late in 1988 the Mt John University Observatory acquired a cryogenic CCD system from Photometrics Ltd (Tucson). The chip is a Thomson CSF TH7882 CDA comprising 384 × 576 pixels. As part of the evaluation process, we have begun two differential photometry programs of the Magellanic Clouds using the Mt John 0.6m Boller & Chivens telescope. On this telescope each CCD pixel corresponds to 0.6 arcsec. Mt John's southerly latitude (44°S) permits year-round observations of the Clouds.

The first program concerns B, V and I photometry of five blue eclipsing binaries selected, on the basis of Gaposchkin's (1970, 1977) photographic light curves, to have roughly equal components with minimal interaction. HV 12634 has also been observed for comparison with the CCD light curves published by Jensen et al. (1988). Fig. 1 shows the B observations so far obtained for HV 1761, but the reduction is preliminary, being based on aperture-integrated magnitudes. The field is populous, and a final reduction will require use of a crowded-field reduction package such as ROMAFOT.
Abundance analysis of six LMC F supergiants
Authors: McWilliam Andrew , Williams Robert E.
Published: July 2016

We have performed an abundance analysis of six Large Magellanic Cloud (LMC) F supergiants, based on infrared photometry and echelle spectra obtained from CTIO. We find a real dispersion in Fe/H values, indicating that the LMC is inhomogeneous. Oxygen abundances appear to be equal in all six stars, resulting in a steep O/Fe slope with Fe/H. Other element abundances appear near normal, although there is a hint of a small enhancement of second s-process peak elements. Iron abundances are probably affected by non-LTE; this does not change our conclusions concerning oxygen.
High velocity clouds near the Magellanic Clouds
Authors: Mebold Ulrich
Published: July 2016

High velocity clouds (HVCs) of neutral atomic hydrogen close to the position of the Magellanic Clouds (MCs) and the Magellanic Stream (Stream) are reviewed. The gas observed at velocities of +70 km/s and +130 km/s in front of the LMC is probably associated with ordinary HVCs in the galactic halo. This is not the case for the gas observed between +150 and +170 km/s which is more likely associated with the MCs. The HVCs observed superimposed onto the Stream are possibly remnants of collisions between a gaseous polar ring around our Galaxy and the bridge region between the MCs. The HVCs found close to and “behind” the tip of the Stream may be regarded as shreds of the Stream precipitating toward the galactic disk. The chemical composition, the radiation field and the temperature in the Stream is discussed in the context of the first spin temperature determination by Wakker (1990), of an HVC.
Radial velocities of clusters between the Magellanic Clouds
Authors: Demers S. , Grondin† L. , Irwin M. J. , Kunkel W.E.
Published: July 2016

Radial velocities of 20 stars members of young clusters and associations located in the inter-Cloud region within 2h < R.A. < 5h tend to be lower than the HI velocities in the same direction. The stellar velocities do not show a pronounced velocity gradiant as observed for the HI from the SMC to the LMC. This suggests that the stellar components belong to the SMC wing. Our photometry and spectroscopy support the view that one of the stars at 4h20m is a foreground HB star.
The role of convective boundaries
Authors: Herwig F. , Blöcker T. , Schönberner D.
Published: July 2016

We investigate the influence of convective overshoot on stellar evolution models of the thermal pulse AGB phase with MZAMS = 3M⊙. An exponential diffusive overshoot algorithm is applied to all convective boundaries during all evolutionary stages.

We demonstrate that overshooting at the bottom of the pulse-driven convective zone, which forms in the intershell during the He-shell flash, leads to more efficient third dredge-up. Some overshoot at the bottom of the convective envelope removes the He-H discontinuity, which would otherwise prohibit the occurrence of the third dredge-up for this stellar mass. However, no correlation between the amount of envelope overshoot and the efficiency of the third dredge-up has been found.

Increasingly efficient third dredge-up eventually leads to a carbon star model. Due to the partial mixing efficiency in the overshoot region a 13C-pocket can form after the third dredge-up event which may be crucial for n-capture nucleosynthesis.
Dredge-Up in Asymptotic Giant Branch Stars
Authors: Mowlavi N.
Published: July 2016

The third dredge-up phenomenon in asymptotic giant branch stars, responsible for the formation of C stars, is discussed based on detailed evolutionary model calculations. The structural readjustment of the star as dredge-up proceeds is analyzed, and its consequences on dredge-up predictions discussed. The question of how to obtain dredge-up in asymptotic giant branch models is also addressed. It is stressed, in particular, that the modeling of dredge-up requires some sort of extra-mixing to be applied below the envelope if the local Schwarzschild criterion is used to delimit convective zones.