bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotation and Abundances in Red Giants
Authors: Barbuy Beatriz
Published: July 2016

The abundances of red giants will be reviewed, in particular those of carbon, nitrogen, oxygen and 12C:13C. The observed abundances are compared to predictions based on recent models with stellar rotation. Three topics will be emphasized: abundances in very metal-poor stars related to a previous generation of supernova; 12C:13C in red giants and rotation induced extra mixing; CNO abundances in yellow supergiants and their connection with models computed with rotation.
Lithium Abundances in Fast Rotating Bright Giant Stars
Authors: do Nascimento J.D. , Lèbre A. , Konstantinova-Antova R. , de Medeiros J. R.
Published: July 2016

We present the results of high resolution spectroscopic observations of Li I resonance doublet at λ 6707.8 Å for fast rotating single stars of luminosity class II and Ib. We present a discussion on the link between rotation and Li content in intermediate mass giant stars, with emphasis on their evolutionary status. At least one of the observed stars, HD 232862, a G8II with an unusual vsini of 20 km/s, present a Li-rich behavior.
Rotation, Convection, Activity and Lithium in Single G and K giants
Authors: Konstantinova–Antova Renada K.
Published: July 2016

We studied the activity and evolutionary stage of 14 low and intermediate mass single giants that should meet the conditions for dynamo action and Li–enrichment. Only small part of them exhibit either moderate to fast rotation and evidences for magnetic activity and/or high Li abundance. There are also intermediate–mass giants with fast rotation, but no evidences for magnetic activity was found in them and their Li–content is low one. on the other hand, no fast rotation and activity were observed in some of the Li–rich giants. There is a large difference in the activity properties and Li content in stars with similar masses and evolutionary stage.
Magnetic Cycles and Rotation in Active Late–Type Stars
Authors: Tuominen Ilkka , Berdyugina Svetlana V. , Korpi Maarit J.
Published: July 2016

Observational evidence, based both on spectroscopic Doppler imaging and long-term photometry, of strongly nonaxisymmetric spot distributions in magnetically very active late-type stars, with a special cyclic behaviour (the “flip-flop” effect), is presented. Theoretical implications of these results are discussed from the point of view of nonlinear mean-field dynamo theory.
Gravitational Distortions of the Shape of the Sun: Constraints on the Models
Authors: Rozelot J. P. , Lefebvre S.
Published: July 2016

Due to its own rotation, it is expected that the visual figure of the Sun is a spheroid; this is not truly the case because the solar rotation is not constant both over all heliographic latitudes and in depth. The photospheric shape is thus sensitive to the interior structure: accurate measurements of both limb shape distortions and solar rotation rates determination provide useful constraints on the internal layers (density, shear zones, …). We show why and how the implication of the successive gravitational moments are important to probe the solar interior, and we compare measurements obtained either from space (SOHO/MDI) or from ground-based experiments (scanning heliometer at the Pic du Midi). The found faint departures to the sphericity, not exceeding 22 mas, could explain fluctuations that are not yet taken into account in the classical modelling of the solar irradiance. A crude model could explain the asphericities which is based on a core rotating at a nearly uniform rate combined with a prolate tachocline and an oblate outer convective zone.
On Rotationally Driven Meridional Flows in Stars
Authors: Garaud P.
Published: July 2016

The first entirely self-consistent 2D model of rotational mixing in a stellar radiative zone is presented. This nonlinear problem is solved numerically assuming axisymmetry of the system. The dynamical behaviour of a rotating star is found to be controlled by one parameter only, the ratio of the Eddington-Sweet timescale to the viscous timescale. In the quasi-steady state, the limit of slow rotation recovers Eddington-Sweet theory, whereas in the limit of rapid rotation, the system settles into a centrifugal equilibrium. The evolution of the dynamical structure of the star undergoing spin-down is then studied, and the relevance of these findings to observations of rotational mixing is discussed.
The Diffusion-Circulation Coupling in Stellar Radiative Zones: 2D Simulation
Authors: Théado Sylvie , Vauclair Sylvie
Published: July 2016

We have done a 2D simulation of meridional circulation in the presence of helium diffusion below stellar convective zones. For slowly rotating stars the microscopic diffusion of helium leads to a μ-gradient which has an important effect on the rotation induced mixing. We present here the results of this 2D simulation for solar type stars.
Simulations of Core Convection Dynamos in Rotating A-type Stars
Authors: Browning Matthew , Brun Allan Sacha , Toomre Juri
Published: July 2016

We have conducted preliminary numerical simulations of a core convection dynamo operating within an A-type star of two solar masses. Convection within the core clearly can admit magnetic dynamo action. Magnetic field strengths in our three-dimensional simulations grow by many orders of magnitude, from an initial seed field to kilo-Gauss levels. We discuss the differential rotation and magnetic field sustained in our simulations.
Multidimensional Hydrodynamic and Hydrostatic Stellar Models
Authors: Deupree Robert G.
Published: July 2016

Results for multidimensional stellar model simulations of both 2D and 3D hydrodynamic models and 2D stellar evolution sequences are presented. Simulations of the highly superadiabatic region of the solar convective region provide a good example of the current status and limitations of explicit 3D finite difference methods in stellar problems. Such simulations cannot be used for stellar cores, where the motion is expected to be well subsonic. The results of some 2D fully implcit hydrodynamic simulations of convective cores and shells are given for models with and without rotation, and their effects examined through fully 2D stellar evolution sequences. One effect of moderate to rapid rotation in convective cores is to alter the convective flow pattern so that convective eddies tend to line up parallel to the rotation axis. Rotation also appears to modestly reduce the amount of convective core overshooting, at least for intermediate mass models.
Oscillations of Fast Rotating Stars: p-Modes in Centrifugally Flattened Polytropes
Authors: Lignières F. , Rieutord M.
Published: July 2016

Oscillation modes of rapidly rotating stars have not yet been calculated with precision, rotational effects being generally approximated by perturbation methods. We developed a mathematical formalism and a numerical method which fully account for the deformation of the star by the centrifugal force. The method has been first tested in the case of Maclaurin spheroids and then applied to uniformly rotating polytropic stars.
Activity, Rotation and Convection in Orion: Are the Data Inconsistent with the Ms Activity-Rossby Number Relation?
Authors: Flaccomio E. , Micela G. , Pizzolato N. , Sciortino S. , Ventura P.
Published: July 2016

A relation between activity and rotation in young ~ 1Myr PMS in often not observed, suggesting that the mechanism responsible for the X-ray emission may differ from the α - ω dynamo. We re-investigate the matter utilizing recent X-ray and rotational data on the Orion Nebula Cluster (ONC).
The Evolution of Angular Momentum of Intermediate Mass Stars: From the Birthline to the Main Sequence
Authors: Wolff S. C. , Strom S. E. , Hillenbrand L. A.
Published: July 2016

Measurements of stars in the Orion OB association show that there is a continuous power law relationship between specific angular momentum (J/M) and mass (M) for stars on convective tracks having masses in the range ~0.5 to ~3 M⊙; this power law extends smoothly into the domain of more massive stars on the ZAMS. If we assume that stars are “locked” to circumstellar accretion disks via their magnetic fields until they are deposited on the stellar birthline, we can account for the observed slope and zero point of the power law fit to the upper envelope of the observed J/M vs M distribution.

Pre-main sequence stars with M<2 M⊙ on radiative tracks do not follow the power law relationship. A sharp decrease in J/M with decreasing mass has been recognized for more than 30 years for older field stars, but remarkably is seen already among our Orion sample of stars that are only a few million years old. We show that this break in the power law is a consequence of loss of angular momentum on convective tracks, combined with core-envelope decoupling at the time of the transition from the convective to radiative tracks.
Evolution of Massive Stars with Rotation and Mass Loss
Authors: Maeder André , Meynet Georges
Published: July 2016

Rotation appears as a dominant effect in massive star evolution. It largely affects all the model outputs: inner structure, tracks, lifetimes, isochrones, surface compositions, blue to red supergiant ratios, etc. At lower metallicities, the effects of rotational mixing are larger; also, more stars may reach critical velocity, even if the initial distribution of rotational velocities is the same.
Rotation and Cataclysmic Variables
Authors: Starrfield Sumner , Sion Edward M. , Szkody Paula
Published: July 2016

Cataclysmic Variables are binary star systems and so are closely connected to the subject of this meeting. The stars revolve around the center of mass of the system. The gas lost by the secondary through the inner Lagrangian point enters the Roche lobe of the white dwarf with the angular momentum of the L1 point and, therefore, forms an accretion disk which rotates around the white dwarf. The gas must lose angular momentum to fall onto the white dwarf, and the white dwarf itself must rotate as it accretes infalling material and angular momentum and is gradually spun up. We will review what is known about these phenomena, and emphasize the new results about the white dwarfs that have been learned in the past few years.
The Enigma of AA Dor
Authors: Rauch Thomas , Werner Klaus
Published: July 2016

AA Dor (LB 3459) is an eclipsing, close binary (P = 0.26 d) consisting of a sdOB primary star and an unseen secondary with an extraordinary small mass. The secondary is possibly a former planet which may have survived a common-envelope phase and has even gained mass.

In order to investigate on an existing discrepancy between the components' mass derived from NLTE spectral analysis and subsequent comparison to evolutionary tracks and masses derived from radial-velocity and the eclipse curves, we performed phase-resolved high-resolution and high-SN spectroscopy with the UVES attached to the ESO VLT. from the obtained spectra, we have determined AA Dor's orbital parameters (P = 22 600.702±0.005 sec, A = 39.19±0.05 km s–1, T0 = 2451917.152690) and the rotational velocity (vrot = 47±5 km s–1) of the primary.
Hubble Space TelescopeUltraviolet Spectroscopy of Central Stars of the LMC Planetary Nebulae
Authors: Arrieta A. , Stanghellini L. , Shaw R. A. , Karakla D.
Published: July 2016

In the quest to understand the origin of Planetary Nebula (PN) morphology, correlations have been sought between the nebular shapes and the evolutionary status of the central stars. Several of the mechanisms proposed to explain asymmetric shapes have a direct link with the central star's evolutionary status. Among the possible mechanisms invoked to produce asymmetric PNs, stellar rotation is certainly an effective one, as several hydrodynamics models have shown. In this work we present Space Telescope Imaging Spectrograph (STIS) UV spectra of a sample of bright LMC PNs and their central stars. LMC PNs distances are known, thus the observed characteristics of the stars translate into absolute physical quantities readily, and provide the safest dataset for theory-observation comparisons. We are planing to fit stellar models to the observed spectra using black-body SEDs and synthetic photometry to estimate stellar temperature and reddening. We are going to use the stellar evolutionary tracks to compare the post-AGB age with the dynamical age from the nebula. P-Cygni profiles will be analyzed in order to determine an approximation of the mass loss rate. Stellar characteristics will be related to the morphology of the nebulae observed by our group with HST STIS optical slitless spectroscopy.
The effects of Rotation on Wolf–Rayet Stars and on the Production of Primary Nitrogen by Intermediate Mass Stars
Authors: Meynet Georges , Pettini Max
Published: July 2016

We use the rotating stellar models described in the paper by A. Maeder & G. Meynet in this volume to consider the effects of rotation on the evolution of the most massive stars into and during the Wolf–Rayet phase, and on the post-Main Sequence evolution of intermediate mass stars. The two main results of this discussion are the following. First, we show that rotating models are able to account for the observed properties of the Wolf–Rayet stellar populations at solar metallicity. Second, at low metallicities, the inclusion of stellar rotation in the calculation of chemical yields can lead to a longer time delay between the release of oxygen and nitrogen into the interstellar medium following an episode of star formation, since stars of lower masses (compared to non-rotating models) can synthesize primary N. Qualitatively, such an effect may be required to explain the relative abundances of N and O in extragalactic metal–poor environments, particularly at high redshifts.
High-Velocity Clouds and the Local Group
Authors: Wakker B. P.
Published: July 2016

I examine some of the evidence relevant to the idea that high-velocity clouds (HVCs) are gas clouds distributed throughout the Local Group, as proposed by Blitz et al. (1999) and Braun & Burton (1999). This model makes several predictions: a) the clouds have low metallicities; b) there should be no detectable Hα emission; c) analogues near other galaxies should exist; and d) many faint HVCs in the region around M 31 can be found. Low metallicities are indeed found in several HVCs, although they are also expected in several other models. Hα emission detected in most HVCs and, when examined more closely, distant (D>200 kpc) HVCs should be almost fully ionized, implying that most HVCs with H I must lie near the Milky Way. No clear extragalactic analogues have been found, even though the current data appear sensitive enough. The final prediction (d) has not yet been tested. on balance there appears to be no strong evidence for neutral gas clouds distributed throughout the Local Group, but there may be many such clouds within 100 or so kpc from the Milky Way (and M31). on the other hand, some (but not all) of the high-velocity O VI recently discovered may originate in hot gas distributed throughout the Local Group.
Hα Distances to High Velocity Clouds
Authors: Bland-Hawthorn Joss , Putman Mary
Published: July 2016

Several observing teams have now obtained deep Hα spectroscopy towards high-velocity clouds (HVCs) which vary in structure from compact (CHVCs) to the Magellanic Stream. Our team has observed clouds which range from being bright (~640 mR) to having upper limits on the order of 30 to 70 mR. The Hα measurements can be interpreted as a distance constraint if we adopt a halo ionization model based on fesc ≈ 6% of the ionizing photons escaping normal to the Galactic disk (fesc ≈ 1 − 2% when averaged over solid angle). The results suggest that many HVCs and CHVCs are within a ~40 kpc radius from the Galaxy and are not members of the Local Group at megaparsec distances. We refer the reader to Putman et al. (2003) for the full version of the paper presented here.
H I Tidal Tails, Bridges and Clouds
Authors: Koribalski Bärbel S.
Published: July 2016

There is plenty of intergalactic HI gas without any obvious stellar content ranging from (1) extended gas envelopes around some normal and peculiar galaxies, (2) tidal tails/bridges in interacting or merging galaxy systems, (3) large-scale rings around early type galaxies, and (4) detached clouds at varying distances from associated galaxies, but there are few or no isolated HI clouds.

The HIPASS Bright Galaxy Catalog, which covers the whole southern sky, contains only one definite extragalactic HI cloud which is located close to the galaxy NGC 2442 whereas it is sensitive to isolated HI clouds with MHI > 106 x D2 M⊙. The space density of HI clouds is therefore about 1/1000th that of galaxies with the same MHI.
HIPASS J0731-69: Tidal Debris, or Primordial Gas Cloud?
Authors: Ryder Stuart D. , Koribalski Bärbel S.
Published: July 2016

We present follow-up high-resolution HI, deep optical, and molecular observations of the intergalactic gas cloud HIPASS J0731-69, and re-examine the question of its origin in light of these new data.
Galaxy Disruption Caught in the Act
Authors: Karick A. M. , Drinkwater M. J. , West M. J. , Gregg M. D. , Hilker M.
Published: July 2016

Direct evidence of stellar material from galaxy disruption in the intra-cluster medium (ICM) relies on challenging observations of individual stars, planetary nebulae and diffuse optical light. Here we show that the ultra-compact dwarf galaxies (UCDs) we have discovered in the Fornax Cluster are a new and easy-to-measure probe of disruption in the ICM. We present spectroscopic observations supporting the hypothesis that the UCDs are the remnant nuclei of tidally “threshed” dwarf galaxies. Deep optical imaging of the cluster has revealed a 43-kpc long arc of tidal debris, flanking a nucleated dwarf elliptical (dE,N) cluster member. We may be witnessing galaxy threshing in action.
Results from a Diffuse Intracluster Light Survey
Authors: Feldmeier John J. , Mihos J. Christopher , Morrison Heather L. , Harding Paul , McBride C.
Published: July 2016

We give an update of our ongoing survey for intracluster light (ICL), in a sample of distant Abell clusters. We find that the amount of intracluster starlight is comparable to that seen in nearby clusters, and that tidal debris appear to be common.
XMM Observations of Abundances in the Intracluster Medium
Authors: Matsushita Kyoko , Ikebe Yasushi , Finoguenov Alexis , Böhringer Hans
Published: July 2016

Based on XMM-Newton observations of M 87 and the Centaurus cluster, abundance profiles of various elements of the intracluster medium (ICM) are derived. The abundances of Si and Fe show strong decreasing gradients. In contrast, the O and Mg abundances are about half of the Si abundance at the center.

From the gas mass to stellar mass ratio and the comparison of Mg abundance with the stellar metallicity, the stellar mass loss from the central galaxies is indicated to be the main source of gas in the very central region of the clusters.

The observed O, Si and Fe abundance pattern determines the contribution of supernova (SN) Ia and SN II, with the abundance pattern of ejecta of SN Ia. Most of the Si and Fe of the ICM in the central region of the clusters comes from SN Ia which occured in the central galaxies. In order to explain the observed O/Si ratio of a half solar, SN Ia products should have similar abundances of Si and Fe, which may reflect dimmer SN Ia observed in old stellar systems.
Young Stars in the Outer Disc of NGC 6822
Authors: G de Blok W. J. , Walter F.
Published: July 2016

We present wide-field optical imaging covering the entire neutral hydrogen disc of the Local Group dwarf galaxy NGC 6822. These observations reveal the presence of numerous young stars at large galactocentric radii. The extended distribution of young stars implies that stars do form in the outer disks of dwarf galaxies; the HI is not necessarily much more extended than the stellar population. This finding has important consequences for the chemical enrichment of the interstellar medium throughout dwarf galaxies.
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
CO-to-H2 Abundance Ratio of the Foreground Gas of the Carina Nebula
Authors: Jong-Ho Shinn , Kwang-Il Seon , Dae-Hee Lee , Kyoung-Wook Min
Published: July 2016

We analyze CO and H2 absorption lines of the foreground molecular cloud in the Carina nebula. We use HST-STIS (Hubble Space Telescope - Space Telescope Imaging Spectrograph) & IUE (International Ultraviolet Explorer) INES data to analyze the A-X (v=0→2) absorption band of CO for several hot stars toward the Carina nebula, while 9 stars of them have FUSE (Far Ultraviolet Spectroscopic Explorer) spectra to analyze the (v=0→4) vibrational band in the Lyman series of H2. The column densities of CO and H2 varies in the vicinity of N(CO) ~ 1013cm−2 and N(H2) ~ 1019cm−2, respectively. The resultant CO-to-H2 abundance ratio is about 10−6. We investigate the variation of the abundance ratio according to the relative position of the target stars to morphology the molecular cloud in the Carina nebula.
Metal Abundances and Kinematics of Ly-α Absorbers
Authors: Levshakov Sergei A.
Published: July 2016

Both high resolution spectra of QSOs observed at the 8-10 m telescopes and advanced methods of data analysis are crucial for accurate measurements of the chemical composition and physical parameters of the intervening clouds. An overview of our recent results obtained with the Monte Carlo inversion (MCI) procedure is presented. This includes: (1) variations of the shape of the local background ionizing continuum in the 1-5 Ryd range at redshift z ~ 2.8 – 3.0; (2) an inverse correlation between the measured metallicity, [C/H], and the absorber line-of-sight linear size, L; (3) a functional dependence between the line-of-sight velocity dispersion, σv, and L.
The Structure of High Redshift Galactic Halos
Authors: Ellison Sara L. , Ibata Rodrigo , Pettini Max , Lewis Geraint F. , Aracil Bastien , Petitjean Patrick , Srianand R.
Published: July 2016

Observations of multiple or lensed QSOs at high redshift can be used to probe transverse structure in intervening absorption systems. Here we present results obtained from STIS spectroscopy of the unique triply imaged QSO APM 08279+5255 at zem = 3.9 and study the coherence scales of intervening low and high ionization absorbers.
The First Sample of Sub-Damped Lyα Systems and their Chemical Properties
Authors: Dessauges-Zavadsky Miroslava , Péroux Céline , D'Odorico Sandro , Kim Tae-Sun , McMahon Richard G.
Published: July 2016

We took advantage of the ESO UVES/VLT archive of quasar spectra to build a homogeneous sample of ‘sub-DLAs’, absorption line systems with HI column densities between 1019 and 2×1020 cm−2. According to Péroux et al. (2002), these systems should contain a major fraction of the neutral hydrogen mass at z > 3.5 and may thus play an important role at high redshift. Twelve sub-DLAs have been identified. We performed a detailed chemical analysis, and addressed the issues of photoionization corrections. We obtained the first sub-DLA chemical abundance data base ideal for the study of a number of interesting properties of these systems. The implication of sub-DLAs in the cosmic metallicity evolution was our main concern. We also undertook a detailed comparison of the sub-DLA chemical properties with the well studied DLAs to see whether the sub-DLAs are associated with a different class of objects.
Molecules in Damped Lyα Systems: Spatial Distribution
Authors: Hirashita Hiroyuki , Ferrara Andrea , Wada Keiichi , Richter Philipp
Published: July 2016

To interpret H2 quasar absorption line observations in DLAs (damped Lyα clouds), we model the H2 spatial distribution within a DLA. Based on numerical simulations of disk structures with parameters similar to those derived for such absorbers, we calculate the H2 distribution as a function of ultraviolet background (UVB) intensity and dust-to-gas ratio. For typical values of these two quantities we find that the area in which the H2 fraction exceeds 10−6 (typical observational detection limit) only covers < 10% of the disk surface, i.e., H2 has a very inhomogeneous, clumpy distribution even at these low abundance levels. This explains the relative paucity of H2 detections in DLAs. We also show the dependence of the covering fraction of H2 on dust-to-gas ratio and UVB intensity and we comment on the physics governing the H2 chemical network at high redshift. We finally comment on our implication on the statistics of the H2 column density distribution.
The M82 Outflow: X-rays as a Probe for Neutral Disk Gas
Authors: Ott Jürgen , Walter Fabian , Kerp Jürgen
Published: July 2016

We present an analysis of X-ray absorption in the nearby starburst galaxy M82. The X-ray attenuating column densities in the northern part of the M 82 outflow can be associated with cold disk gas detected in maps of H1 and CO (1→0). We derive an XCO factor which is somewhat lower as compared to that in our Galaxy. This is in good agreement with multi-transition line studies of various molecules in the disk of M 82.
Simulating Metal Distributions in the ICM
Authors: Cress C. M.
Published: July 2016

The metal enrichment of the intra-cluster medium within a hierarchical structure formation scenario is investigated using a combination of N-body + Hydro simulations and semi-analytic models of galaxy formation. In our simulation, rates and sites of star formation are identified and gas particles in the environment of these ‘galaxies’ are then enriched with metals using various prescriptions. We investigate the paths of enriched particles, demonstrating how gas enriched at higher redshifts is distributed in a cluster after it has formed. We are then able to predict a number of observable quantities such as the radial profiles of metals from both SNII and SNIa and the evolution of metal content with redshift.
Warm Winds in the Seyfert 1 Galaxy NGC 5548
Authors: Steenbrugge K. C. , Kaastra J. S.
Published: July 2016

We present the results of a recent long XMM-Newton and Chandra observation on the Seyfert 1 galaxy NGC 5548. This galaxy has a warm absorber with a wide range of ionization stages. The detection of O VI in both the UV and X-rays allows for a direct comparison of the measured column density in both wavelength bands. We also comment on the detection of O V, and its newly measured wavelength.
Synchrotron Jet Model for the 1989-1996 Cycle of Activity of NGC 4151
Authors: Pronik I. I.
Published: July 2016

Observational data from the X-ray through the UV and optical of variations of the NGC 4151 nucleus were compiled. The characteristics of the variability related to the 1989-1996 cycle of activity show remarkable similarity to those of blazars and do not contradict the supposition that this cycle of activity was caused by a synchrotron jet (SJ). Some of the activity of previous cycles were interpreted in the framework of a SJ model and some of that of a disc instability model (DI). We ask the question if different cycles of activity can be of a different nature caused by a different accretion rate.
Absorption Components in the Nucleus of NGC 3227
Authors: Xu Dawei , Komossa Stefanie , Burwitz Vadim , Predehl Peter
Published: July 2016

X-ray spectroscopy provides a wealth of information about the properties of the surrounding reprocessing material of AGN. We present results from a 96 ks exposure of NGC 3227, taken with the Low Energy Transmission Grating Spectrometer on board the Chandra X-ray Observatory. A partial covering model fits well the resulting X-ray spectrum. We investigate the dusty nuclear environment of this galaxy, and in particular concentrate on its warm absorber.
Ram Pressure Stripping of Spiral Galaxies in Clusters
Authors: Schumacher Elke , Hensler Gerhard
Published: July 2016

We investigate the process of ram pressure stripping by means of numerical simulations with a 2D hydrodynamical code. We present some first results of a set of simulations with varying galaxy velocities and ICM densities. We find that in typical cluster core environments disk galaxies lose a substantial amount of their gas, whereas in the outskirts of galaxy clusters the mass loss is quite small. Furthermore, the gas loss happens in two phases: In the initial phase gas is pushed out of regions where the ram pressure overcomes the gravitational restoring force; most of the overall gas loss happens in this phase. Afterwards the Kelvin-Helmholtz instability leads to a further mass loss at a small rate, that could be important on long timescales.
Ram Pressure Effects on the Magnetic Field of NGC 2442
Authors: Fletcher A. , Beck R. , Harnett J. , Ehle M. , Ryder S.
Published: July 2016

The λ6 cm radio continuum emission from the barred galaxy NGC 2442 displays several unusual features that are probably due to the interaction of the galaxy with the intergalactic medium.
Mass Stripping in Dwarf Spheroidal Galaxies and ω Cen
Authors: Tsujimoto Takuji , Shigeyama Toshikazu
Published: July 2016

The stellar abundance pattern of neutron-capture elements such as Ba is used as a powerful tool to infer how star formation proceeded in dwarf spheroidal (dSph) galaxies. It is found that the abundance correlation of Ba with Fe in stars belonging to dSph galaxies have a feature similar to the Ba-Fe correlation in Galactic metal-poor stars. The common feature of these two correlations implies that dSph stars formed from gas with a velocity dispersion of ~26 km s−1. This velocity dispersion together with the stellar luminosities strongly suggests that dark matter dominated dSph galaxies. The tidal force of the Milky Way links this velocity dispersion with the currently observed value ≤ 10 km s−1 by stripping the dark matter in dSph galaxies. We also investigate the ram pressure exerted on the gas in ω Cen. It is found that the ram pressure is not strong enough to strip the gas but is expected to induce a bulk motion of the gas during the star formation epoch which is compatible with the recent observed finding and then the remaining gas after the star formation is likely to be stripped due to the gradual increase in the gas density in the forming Galactic disk.
The Galaxy's Eating Habits
Authors: Putman M. E. , Thom C. , Gibson B. K. , Staveley-Smith L.
Published: July 2016

The possibility of a gaseous halo stream which was stripped from the Sagittarius dwarf galaxy is presented. The total mass of the neutral hydrogen along the orbit of the Sgr dwarf in the direction of the Galactic Anti-Center is 4 − 10 × 106 M⊙ (at 36 kpc, the distance to the stellar debris in this region). Both the stellar and gaseous components have negative velocities in this part of the sky, but the gaseous component extends to higher negative velocities. We suggest this gaseous stream was stripped from the main body of the dwarf 0.2 – 0.3 Gyr ago during its current orbit after a passage through a diffuse edge of the Galactic disk with a density > 10−4 cm−3. The gas would then represent the dwarf's last source of star formation fuel and explains how the galaxy was forming stars 0.5-2 Gyr ago.
A Fourier Analysis of the Interacting Pair of Galaxies KPG 404 (NGC 5394/95)
Authors: Puerari Ivânio , Valdez-Gutiérrez Margarita , Hernández-López Izbeth
Published: July 2016

We present a bi-dimensional Fourier analysis of near-infrared images of KPG 404 (NGC 5394/95). The 2D Fourier analysis shows that NGC 5394 is a H2β galaxy in the DP classification (Block & Puerari 1999). In contrast, NGC 5395 displays a very complex structure which needs a number of Fourier coefficients to be explained. A tightly wound m = 1 (DP class H1α) is the main structure, but other m = 1 and m = 2 coefficients (suggesting spiral arm modulation) are also present in the Fourier spectra. The complex structure of NGC 5395 also suggests a strong interaction in the pair. The m = 1 coefficients can represent a pseudo ring-type structure, resulting of a collision rather than a grazing passage. We conclude that the most probable scenario of the interaction in this pair should take into account a crossing of NGC 5394 through the disk of NGC 5395.
Some Effects of Galaxy Collisions in a Cluster ICM
Authors: Struck Curtis , Brown Jason R.
Published: July 2016

We present preliminary results of numerical modeling of the combined effects of ICM stripping and galaxy collisions on galaxies in clusters. We use the Hydra adaptive mesh, P3M + SPH code of Couchman et al. (1995). Generally, the formation of extended tidal and splash structures in galaxy interactions will facilitate ram pressure stripping. ICM compression of massive clouds stripped from tails and plumes may produce significant populations of free-floating star clusters or dwarf galaxies.
Environmental Effects on the Kinematics of Virgo Cluster Galaxies
Authors: Chemin L. , Cayatte V. , Balkowski C. , Amram P. , Marcelin M. , Garrido O. , Boulesteix J. , Carignan C. , Boselli A. , Vollmer B. , Adami C. , Hernandez O.
Published: July 2016

We present results from an ongoing survey of the ionized gas kinematics in Virgo cluster spiral galaxies using Fabry-Perot (FP) interferometry. Our goal is to study the environmental effects on galaxy evolution in the Virgo cluster. We report here on the Hα distribution map and velocity field of NGC 4438, an interacting galaxy near the centre of the cluster.
Molecular Gas and Star Formation in the NGC 3077 Tidal Arm
Authors: Walter Fabian , Martin Crystal , Ott Jürgen , Heithausen Andreas
Published: July 2016

We report the discovery of extended star formation in the prominent tidal arms near NGC 3077 (member of the M 81 triplet). 36 faint compact star forming regions were identified, covering an area of 4 × 6 kpc2. HII regions are only found near the southern rim of the tidal HI arm where the HI column density reaches values above 1 × 1021 cm−2. This threshold is very similar to what is found in ‘normal’ galactic environments. We derive a total star formation rate of 2.6 × 10−3M⊙ yr−1 in the tidal feature. We also present the first high-resolution observations of molecular gas in this region. The molecular gas emission can be separated into at least 5 distinct complexes most of which do not coincide with sites of star formation. The reservoir of neutral and molecular gas in the tidal arm is huge (~5 × 108M⊙); star formation may continue at the given rate for a Hubble time. We conclude that wide-spread low-level star formation may be a common phenomenon in tidal HI tails, however it will be difficult to detect in interacting systems that are further away.
Study of HI and Star Formation Sites in the Magellanic Bridge
Authors: Muller Erik , Staveley-Smith Lister , Zealey William
Published: July 2016

Tidal features represent an important process for the recycling of matter across extremely large spatial scales. The Magellanic Bridge is the closest gaseous tidal feature to our own Galaxy, and offers an ideal opportunity to study the active processes in such phenomena at high spatial resolutions otherwise unavailable. The neutral hydrogen of the western Magellanic Bridge, has been observed with both the Parkes 64m telescope and ATCA interferometer and the resulting dataset has revealed an extremely complex and chaotic morphology. We discuss these observations here with reference to a variety of analyses: the spatial correlation of apparently expanding HI shells with OB associations and the outcome of sensitive Hα and CO surveys.
The Dynamical Masses of Tidal Dwarf Galaxies
Authors: Hibbard J. E. , Barnes J. E.
Published: July 2016

A variety of substructures have been identified within the tidal debris around interacting galaxies. These structures range in scale from Globular Clusters to the so-called “Tidal Dwarf Galaxies”. We review observations of such objects, with particular emphasis on what can be inferred from dynamical mass estimates. We then present the results of a dynamical analysis of structures which develop within the tidal tails of a large-N numerical simulation (N~1 million). We find that under the best conditions, “observations” of this system recover the true mass of the bound substructures to within a factor of two. Poor spatial and velocity resolution (coarser than the true half-light radii and velocity dispersions) and more inclined viewing geometries lead the dynamical masses to be over-estimated by factors of ten or more. A combination of poor resolution and edge-on viewing geometries lead to the most dramatic discrepancies, with dynamical masses over-estimated by factors of up to 1000. Furthermore, projection effects can lead to apparent concentrations of material at the ends of tidal tails that is in reality spread over very large distances, with mass scales well beyond that of any truly bound regions. Since many of the well studied tidal dwarf candidates are found within edge-on tails, we conclude that their mass and extent may have been greatly over-estimated.
Identifying old Tidal Dwarf Galaxies in Simulations and in the Nearby Universe
Authors: Duc Pierre-Alain , Bournaud Frédéric , Masset Frédéric
Published: July 2016

Most Tidal Dwarf Galaxies (TDGs) so-far discussed in the literature may be considered as young ones or even newborns, as they are still physically linked to their parent galaxies by an umbilical cord: the tidal tail at the tip of which they are usually observed. Old Tidal Dwarf Galaxies, completely detached from their progenitors, are still to be found. Using N-body numerical simulations, we have shown that tidal objects as massive as 109 solar masses may be formed in interacting systems and survive for more than one Gyr. Old TDGs should hence exist in the Universe. They may be identified looking at a peculiarity of their “genetic identity card”: a relatively high abundance in heavy elements, inherited from their parent galaxies. Finally, using this technique, we revisit the dwarf galaxies in the local Universe trying to find arguments pro and con a tidal origin.
An X-ray image of the Large Magellanic Cloud: detection of the hot interstellar medium
Authors: Helfand D. J.
Published: July 2016

We report the results of a comprehensive reanalysis of the X-ray imaging data for the Large Magellanic Cloud obtained with the Einstein Observatory. A map covering 37 deg2 of the Cloud is presented. The total 0.15–3.5 keV luminosity is ˜ 5 × 1038erg s--1, two thirds of which can be attributed to the 105 identified discrete emitters and the remainder of which arise from the coronal component of the interstellar medium at temperatures from ˜ 2 to ˜ 10 × 106K. The energy balance for this hot ISM and the morphology of specific regions such as 30 Doradus and LMC-2 are briefly discussed.
Where is the rotation centre of the LMC?
Authors: Wielebinski R. , Bajaja E.
Published: July 2016

The structure of the Large Magellanic Cloud (LMC) has posed many questions and has led to many controversial discussions. Although classified as an 'irregular', repeated claims have been made suggesting that the LMC has spiral structure. Furthermore, this 'spiral' structure seems to originate in the 30-Doradus nebula which, as a result, was sometimes referred to as the 'nucleus' of the LMC. We summarize the recent data on the LMC and re-examine the HI data to point out that possibly different rotation centres exist for different components.
Hi-distribution, kinematics and geometry of the Large Magellanic Cloud
Authors: Rohlfs K. , Luks Th.
Published: July 2016

Here we discuss current observational data on, and the distribution of, neutral hydrogen in the Large Magellanic Cloud (LMC).
Large scale structure and kinematics of the LMC from a study of long-period variable stars
Authors: Hughes Shaun M.G. , Wood Peter R. , Reid Neill
Published: July 2016

A recently completed study of the kinematics of Long-Period (or red) Variables (LPVs) in the LMC by Hughes et al. (1990) has shown that those with short periods (100 to 225 days) have spheroidal kinematics (high velocity dispersion and low rotational velocity about the LMC). This is the first evidence of the LMC's possessing a spheroidal population. The spheroid is flattened (with axial ratio c/a ˜0.3 to 0.5), and is not much thicker than the intermediate age disk. The velocity distribution of the old LPVs indicates that the mass of the LMC is ˜ 6.2 ± 1.5 × 109M, and that of the spheroid represented by the old LPVs is ˜2 % of the LMC's total mass. If these old LPVs are members of the LMC's disk, then their velocity dispersion implies that they have an age of ˜10 Gyr. The LPVs with intermediate periods (225 to 450 days) are members of the LMC's rotating disk population, with an age ˜4 Gyr derived from their velocity dispersion, and similar to that of the planetary nebulae, CH stars and old cluster populations.
Large-scale structure of the Magellanic Clouds using planetary nebulae
Authors: Meatheringham S. J.
Published: July 2016

The Small and Large Magellanic Clouds (SMC, LMC) are of considerable interest from a kinematical viewpoint. The tidal interation of the Clouds with each other and with the Galaxy appears to have been quite significant in recent times (Murai & Fujimoto 1980). The SMC in particular appears to have been considerably disrupted by a recent close passage to the LMC (Mathewson & Ford 1984, Mathewson 1984, Mathewson et al. 1986). For the LMC Freeman et al. (1983) found that the young and old populations have significantly different rotation solutions.

Planetary Nebulae (PN) form a population with age intermediate between the HI and young clusters and the old Population II clusters. A large number of PN are known in the MCs. Sanduleak et al. (1978) compiled a list of 102 in the LMC and 28 in the SMC. Since then other authors have increased the total number known to approximately 140 in the LMC and 50 in the SMC.
Fast shells and X-ray emission in 30 Doradus: SNRs and superbubbles
Authors: Chu You-Hua , Kennicutt Robert C.
Published: July 2016

We have mapped the kinematics of the ionized gas in 30 Dor, and find numerous examples of fast expanding shells. There is good correlation between the high-velocity material and the bright diffuse X-ray emission in 30 Dor. The fast shells are probably supernova remnants, stellar wind-blown bubbles, or combinations of both.
X-rays from superbubbles in the Large Magellanic Cloud
Authors: Chu You-Hua , Mac Low Mordecai-Mark
Published: July 2016

We find diffuse X-ray emission not associated with known SNRs in seven LMC HII complexes. All, except 30 Dor, have simple ring morphologies, indicating shell structures. Assuming these are superbubbles, we find the X-ray luminosity expected from their hot interiors to be an order of magnitude lower than the observed value. SNRs close to the center of a superbubble add very little emission, but we calculate that off-center SNRs hitting the ionized shell could explain the observed emission.
IR characteristics of Type II Cepheids in the LMC and in the Galaxy
Authors: Laney C. David
Published: July 2016

JHK observations have been obtained of Type II Cepheids in the LMC, in globular clusters, and in the galactic field. The P-L relations at J and H imply an LMC distance modulus consistent with Mv˜0.6 for RR Lyrae stars. Modest excesses at K are seen in some LMC objects. One previously reported LMC Type II Cepheid appears to be a Type I Cepheid, and two others are much redder in J-H than normal Type II Cepheids. HV11211 is a Type I Cepheid in the SMC.
AST/RO and submillimetre-wave observations of the Magellanic Clouds from the South Pole
Authors: Lo K.Y. , Stark A.A. , Bally J. , Wilson R.W. , Bania T. , Lane A.
Published: July 2016

AST/RO (Antarctic Submillimeter Telescope and Remote Observatory), a joint project between AT&T Bell Labs, Boston University and the University of Illinois, will place a 1.7-m submillimetre telescope at the South Pole (a high, dry site) in 1992. The highly automated off-axis parabolic telescope will be equipped initially with two channels of 500 GHz (600 μm) heterodyne receivers and AOS spectrometers. A primary goal of the project is a large-scale survey of CI and CO(4-3) line emission from the southern Galaxy and the Magellanic Clouds, in an effort to further the understanding of the warm interstellar medium and star formation in the two galaxies.
Magellanic globulars as cosmological tools
Authors: Renzini Alvio
Published: July 2016

The globular clusters (GC) of the Magellanic Clouds play a very important role for many astrophysical and cosmological topics. For example, they represent the ideal testground for stellar evolution theory, they allow us to study the the early dynamical evolution of star clusters, to obtain accurate initial mass functions in a fairly extended mass range, to calibrate the Cepheid period-luminosity relation, and so on. In this brief paper I will touch upon two items which are of considerable cosmological interest, and about which Magellanic Cloud globulars provide unique information. These topics concern i) GC formation in galaxies, and ii) the epoch of galaxy formation.
Mass to light ratios of Large Magellanic Cloud clusters
Authors: Mateo Mario , Welch Douglas , Fischer Phil
Published: July 2016

The massive star clusters of the Large Magellanic Cloud (LMC) are ideal laboratories for the study of the dynamical evolution of rich stellar systems. Not only do they contain large numbers of stars but, unlike the Galactic globular clusters, LMC clusters span a large range in age. Here we describe a continuing project to determine the temporal evolution of the mass-to-light (M/L) ratio of LMC clusters and present some preliminary results.
The age distribution function of star clusters in the LMC
Authors: Alongi M. , Chiosi C.
Published: July 2016

We present the age distribution function for Large Magellanic Cloud (LMC) clusters obtained from a relationship between their integrated U BV colours and age. We discuss further the results by Chiosi et al. (1988) on the nature of the bimodal distribution of the (B - V) colours for LMC clusters. Their conclusion that bimodality in the colour stems from the combined effect of the age distribution function and the rate at which clusters change colour with age, is revisited. The result of our analysis shows that the age distribution is the sole agent and that a real age gap is present. Finally, we draw some conclusions about the efficiency of cluster formation and disruption in the LMC.
A search for non-thermal emission in the HII regions of the Magellanic Clouds
Authors: Amy S. W.
Published: July 2016

The 843 MHz radio survey of the Magellanic Clouds with the Molonglo Observatory Synthesis Telescope (MOST) has provided continuum images with a resolution of about 45 arcsec for many HII regions. By comparing these radio data with H-alpha data regions of non-thermal emission may be found within HII regions.