bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature shocks at the origin of regolith on asteroids
Authors: Michel Patrick , Delbo Marco , Libourel Guy , Ganino Clément , Verati Chryst'le , Rémy Benjamin
Published: March 2015

Space-based and remote sensing observations reveal that regolith – a layer of loose unconsolidated material – is present on all asteroids, including very small, subkm-sized near- Earth asteroids (NEAs) such as (25143) Itokawa. Classically, regolith is believed to be produced by the ejecta of impact craters produced by small particles hitting asteroid surfaces. Such an explanation works for bodies whose gravity field is strong enough for substantial reaccretion of impact debris, but it fails to account for the ubiquitous presence of regolith also on small asteroids with weaker gravity. Several works have proposed that the thermal fatigue due to a huge number of day/night temperature cycles is a process that contributes to the formation of regolith on the Moon, Mercury, and on the NEA (433) Eros by fracturing boulders and rocks on their surfaces. However, this process lacks a demonstration: in order to study under which conditions rock cracking on NEAs occurs, we calculated typical temperature cycles for NEAs and we performed laboratory experiments of similar thermal cycling on meteorites taken as analogue of asteroid surface material. We will present results of these experiments and discuss their implications regarding regolith formation on asteroids.
Brief Introduction of Promoting the Chinese Program For Exploring the Martian System
Authors: Ping Jinsong , Shi Xian , Jian Nianchuan , Zhang Sujun , Wang Mingyuan , Shang Kun ,   Yinghuo-1 VLBI team
Published: March 2015

Following the progress of Chinese deep space exploration step, since 2006 we started a Mars mission, Yinghuo-1, by join in the Phobos-Grunt mission of Russia. A satellite bus platform and onboard payloads as well as an innovative open-loop radio tracking system have been developed by mission team. Also, together with Russian and German colleagues, we developed a kind of in-beam tracking method for measuring the rotation and nutation of Phobos, and developed the 1st Phobos global gravity field for the mission. We are promoting the Chinese new mission for Mars exploration. Although the joint YH-1 & Phobos-Grunt mission failed, the new techniques and knowledge developed by mission teams may benifit the future missions. In fact, the open-loop technique have been applied into lunar and other planetary missions, and the method in developing Phobos global gravity field will be used in the study of Rosetta mission and future Chinese mission for small body.
Jovian impact flashes and their implication to small bodies
Authors: Watanabe Junichi
Published: March 2015

Optical flashes on the surface of Jupiter were observed by amateur astronomers in June and August 2010. It is thought that these phenomena were bright meteors caused by the collision of small celestial bodies of a few to 10-m, and that they seemed to be more frequent than expected. If the frequency and the scale of these phenomena are investigated, the size distribution down to size of a few m can be decided at around the giant planet region. If the systematic observation is achieved, it will be a unique attempt to use the giant planets as a natural detector of small bodies.
The physical-chemical properties of substance of the bright fireball EN171101 Turyi Remety
Authors: Churyumov Klim , Belevtsev Rudolf , Sobotovich Emlen , Spivak Svitlana , Churyumova Tetyana
Published: March 2015

In 2007-2011 searches were conducted for mineralogical and geochemical studies of the soil in the region of fall down of a bright fireball EN171101 “Turyi Remety“ matter in Perechyn district of Transcarpathian. In the assumed location of the fall of a meteorite material for analysis was taken from the bottom of streams of Transcarpathian Mountains. In this matter we have been found numerous small magnetic spheres (microspherul) and fused segments, which have enough large sizes - up to 5 mm in diameter, which probably are fragments of the Turyi Remety meteoroid. One of the known signs of fireballs are sand-sized magnetic balls (by diameter 0.1-1.0 mm), which are often found in the magnetic concentrate fraction. This small balls, together with fragments of fused iotsit (FeO) are formed during the ablation of the meteoroid, and their sizes decreases during the motion of the meteoroid in the Earths atmosphere. From the east to the west, the radius of the balls in the study area decreased from an average of 0.7-0.5 mm to 0.1-0.3 mm. The sizes of such balls, as glowing molten particles of the meteoroid, are in good agreement with calculations based on the energy loss of the Turyi Remety meteoroid. This confirms the cosmic origin of these found small balls. Pre-calculated physical parameters of the Turyi Remety meteoroid are the velocity, mass, kinetic energy, the resistance force during ablation, the average fireball particle radius along trajectory path of a meteoroid fragments depending from the mass and size. Rapid mass loss of the meteoroid in more than 10 times, stronger, shorter ablation and damping fireball at the high altitude say about instability and the participation of the meteoroid gas in ablation. Perhaps the presence of ice, and other fireball gases in the meteoroid composition shows that its composition was close to comet one or to a chondrite with ice (gas hydrates). Especially likely gaseous hydrates of heavy gases such as CO2, H2S, hydrocarbons (propane, butane, etc.).
Influence of thermal models on the YORP effect
Authors: Golubov Oleksiy , Krugly Yurij N.
Published: March 2015

In 1-D heat conductivity model, the YORP acceleration is proved to be independent of the asteroid's heat properties. Considering small structures on the surface of an asteroid breaks 1-D model. A new force appears, pulling the asteroid's surface parallel to itself. Its effect on the asteroid's rotation is called tangential YORP, or TYORP.
Determination of the rotational period of the comet 29P/Schwassmann-Wachmann-1 using dynamics of the dust structures (jets) in the coma
Authors: Ivanova Aleksandra , Afanasiev Viktor , Korsun Pavlo , Baransky Aleksandr , Andreev Maksim , Ponomarenko Vasyliy
Published: March 2015

We present analysis of the photometric data of the distant comet 29P/Schwassmann-Wachmann-1, obtained at the 6-m BTA telescope (SAO RAS, Russia) and at the 2-meter telescope Zeiss-2000 (ICAMER, KB). The comet shows significant jets activity at large heliocentric distances, beyond the zone of water ice sublimation. Various digital filters were applied to increase the contrast of the jets and separate them. The rotation period of the nucleus was derived using cross-correlation method. The value of the rotation period is 12.1 ± 1.2 days for observations made in 2008 and 11.7 ± 1.5 days for observations made in 2009.
Identification of radiants of low-light-level meteors from double station TV observations during autumnal equinox of 2001 and 2003
Authors: Kozak Pavlo M. , Rozhilo Olexander O. , Taranukha Yuriy G.
Published: March 2015

Results of double-station TV meteor observations which were carried out during autumnal equinox in 2001 and 2003 are used for the confirmation of existing meteor showers and for a search for probable new micro-showers. Seven existing September showers were confirmed, two of them by meteors from both years. Fourteen new groups were proposed to be considered as new meteor micro-showers. Taking into account similar kinematical parameters two of them can be supposed to be a part of already existing showers.
Meteor studies applying incoherent scatter radar instruments
Authors: Mann Ingrid , Pellinen-Wannberg Asta , Tjulin Anders
Published: March 2015

One of the interesting aspects of optical meteor studies is that the spectral composition of the brightness reveals information about the element composition of the solid particles that enter Earthfs atmosphere from interplanetary space. Deriving composition from optical spectra requires understanding the entry process during which the entering solid interacts with atmospheric species. This is especially so, because most meteors are observed at altitudes where the mean free path changes from tens of meters to millimeters, that is in the 120 km to 80 km altitude range within the atmosphere. The ionization that causes optical emission also reflects radio waves, so that meteors are observed with different kinds of radar instruments. Incoherent scatter radar facilities are in particular designed to study the upper atmosphere by using the backscattering from free electrons and are basically High Power Large Aperture radars. During the past 15 years they have been increasingly used for meteor studies. The phased-array incoherent scatter radars that are currently under development, such as the planned EISCAT-3Dsystem in northern Scandinavia, will further improve the spatial and time resolution of radar observations and will allow simultaneous measurements of the meteors and of the parameters of the surrounding ionosphere. Radar backscattering is also sensitive to objects that are smaller than those detected optically, so that the observations also permit studying the extension of the meteoroid size distribution to smaller sizes. In this presentation we consider the possibilities for measurements with the future EISCAT-3D as a new path of studying the physics of meteor phenomena with high accuracy.
The current state and prospects for meteors observations in RI NAO
Authors: Shulga A. , Kulichenko N. , Vovk V. , Kozyryev Y. , Sybiryakova Y.
Published: March 2015

The observations of meteors using optical telescopes equipped with TV-cameras and the observations in radio signals using FM radio and TV translators are started in RI NAO since 2010.
Strategy for NEO follow-up observations
Authors: Tichy Milos , Honkova Michaela , Ticha Jana , Kocer Michal
Published: March 2015

The Near-Earth Objects (NEOs) belong to the most important small bodies in the solar system, having the capability of close approaches to the Earth and even possibility to collide with the Earth. In fact, it is impossible to calculate reliable orbit of an object from a single night observations. Therefore it is necessary to extend astrometry dataset by early follow-up astrometry. Follow-up observations of the newly discovered NEO candidate should be done over an arc of several hours after the discovery and should be repeated over several following nights. The basic service used for planning of the follow-up observations is the NEO Confirmation Page (NEOCP) maintained by the Minor Planet Center of the IAU. This service provides on-line tool for calculating geocentric and topocentic ephemerides and sky-plane uncertainty maps of these objects at the specific date and time. Uncertainty map is one of the most important information used for planning of follow-up observation strategy for given time, indicating also the estimated distance of the newly discovered object and including possibility of the impact. Moreover, observatories dealing with NEO follow-up regularly have prepared their special tools and systems for follow-up work. The system and strategy for the NEO follow-up observation used at the Klet Observatory are described here. Methods and techniques used at the Klet NEO follow-up CCD astrometric programme, using 1.06-m and 0.57-m telescopes, are also discussed.
Long term stability of atomic time scales
Authors: Petit G. , Arias F.
Published: March 2015

We review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are in the low 10−16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10−16 value could be reached or superseded and which are the present limitations to attain this goal.
Multiple stellar populations in the massive clusters M22 and Omega Centauri
Authors: Marino A. F.
Published: March 2015

An intriguing discovery in the field of multiple stellar populations in globular clusters is that some of them show internal variations in the bulk of the heavy-element content. I summarize the chemical properties of one of these clusters, M22, in comparison with the most extreme ω Centauri, underlying the analogies and differences between the two objects.
Precision Chemical Abundance Measurements
Authors: Yong David , Grundahl Frank , Meléndez Jorge , Norris John E.
Published: March 2015

This talk covers preliminary work in which we apply a strictly differential line-by-line chemical abundance analysis to high quality UVES spectra of the globular cluster NGC 6752. We achieve extremely high precision in the measurement of relative abundance ratios. Our results indicate that the observed abundance dispersion exceeds the measurement uncertainties and that many pairs of elements show significant correlations when plotting [X1/H] vs. [X2/H]. Our tentative conclusions are that either NGC 6752 is not chemically homogeneous at the ≃0.03 dex level or the abundance variations and correlations signify star-to-star He abundance variations.
Terzan 5: a pristine fragment of the Bulge
Authors: Ferraro Francesco R.
Published: March 2015

We have discovered that Terzan 5, a stellar system in the Galactic Bulge, harbors two stellar populations with different iron content (Δ[Fe/H] ~ 0.5 dex) and possibly different ages. Moreover, the observed chemical patterns significantly differ from those observed in any known genuine globular cluster. These evidences demonstrate that, similarly to ω Centauri in the Halo, Terzan 5 is not a globular cluster, but a stellar system that was able to retain the gas ejected by violent supernova explosions. Moreover the striking chemical similarity with the Bulge stars suggests that Terzan 5 could be the relic of one of the massive clumps that contributed (through strong dynamical interactions with other pre-formed and internally-evolved sub-structures) to the formation of the Galactic Bulge.
Population Models for Massive Globular Clusters
Authors: Lee Young-Wook , Joo Seok-Joo , Han Sang-Il , Na Chongsam , Lim Dongwook , Roh Dong-Goo
Published: March 2015

Increasing number of massive globular clusters (GCs) in the Milky Way are now turned out to host multiple stellar populations having different heavy element abundances enriched by supernovae. Recent observations have further shown that [CNO/Fe] is also enhanced in metal-rich subpopulations in most of these GCs, including ω Cen and M22 (Marino et al. 2011, 2012). In order to reflect this in our population modeling, we have expanded the parameter space of Y2 isochrones and horizontal-branch (HB) evolutionary tracks to include the cases of normal and enhanced nitrogen abundances ([N/Fe] = 0.0, 0.8, and 1.6). The observed variations in the total CNO content were reproduced by interpolating these nitrogen enhanced stellar models. Our test simulations with varying N and O abundances show that, once the total CNO sum ([CNO/Fe]) is held constant, both N and O have almost identical effects on the HR diagram (see Fig. 1).
How did globular clusters lose their gas?
Authors: Charbonnel C. , Krause M. , Decressin T. , Meynet G. , Prantzos N. , Diehl R.
Published: March 2015

We summarize the results presented in Krause et al. (2012a, K12) on the impact of supernova-driven shells and dark-remnant accretion on gas expulsion in globular cluster infancy.
Formation, Growth, and Destruction of Nuclear Star Clusters
Authors: Böker Torsten
Published: March 2015

This talk is an attempt to combine recent insights into the nature of the nuclear star clusters in galaxies of various morphologies into a coherent (albeit simplistic) picture for their formation, growth, and eventual destruction.
The Nuclear Star Cluster of the Milky Way
Authors: Schödel R.
Published: March 2015

This contribution briefly summarizes the current state of our knowledge about the Milky Way's nuclear star cluster.
Overview of dynamical mechanisms of secular evolution
Authors: Pfenniger Daniel
Published: March 2015

Gravity-bound isolated systems, from stars, planetary systems, star clusters to galaxies, share common properties where evolution is the rule. Typically if they start forming at a well defined epoch they tend to change significantly over a timescale comparable to their present age. So evolution is never truly stopped, it just proceeds slower and slower: after a rapid, violent phase a slower, secular phase follows. In galactic astronomy for many decades the paradigm was rather that after a short violent time galaxies would settle in a stable steady state just consuming gas into stars. Actually today it appears that the progressive appearance of galaxy systematic morphologies and the slowing pace of mergers indicate that common intrinsic dynamical factors continue to shape galaxies towards similar properties irrespective of their largely different formation histories and initial conditions. Newtonian physics supplemented by a weakly dissipative component provides an amazing amount of explanations for the galaxy properties, like exponential stellar disks, spirals, bars, and peanut-shaped bulges. The purpose of this talk is to review these mechanisms of dynamical secular evolution.
The role of collective effects and secular mass migration on galactic transformation
Authors: Zhang Xiaolei , Buta Ronald J.
Published: March 2015

During the lifetime of a galaxy, secular radial mass redistribution is expected to gradually build up a bulge and transform the Hubble type from late to early. The dominant dynamical process responsible for this transformation is a collective instability mediated by density-wave collisionless shocks (Zhang 1996, 1998, 1999). The ability of this new mechanism to secularly redistribute the STELLAR mass provides a general pathway for the formation and evolution of the majority of Hubble types, ranging from late type disk galaxiess to disky ellipticals. ATLAS3D results (Cappellari et al. 2013) showed that spirals and S0s and disky ellipticals form a continuous trend of evolution which also coincides with the aging of the stellar population of galactic disks. The importance of stellar accretion is also revealed in the results of the COSMOS team which showed that the evolution of the black-hole-mass/bulge-mass correlation since z = 1 was mainly due to the mass redistribution on pre-existing STELLAR disks which were already in place by z = 1 (Cisternas et al. 2011). The weaker correlation between the masses of late-type bulges and AGNs observed at any given epoch in our view is a result of the quicker initial onset of accretion events in AGN disks compared to that in galactic disks, since the dynamical timescale is shorter for smaller AGN accretion disks.

The same secular dynamical process can produce and maintain the well-known scaling relations and universal rotation curves of observed galaxies during their Hubble-type transformation (Zhang 2008), as well as reproduce many other observed structural and kinematic properties of galaxies such as the size-line-width relation of the interstellar medium and the age-velocity dispersion relation of solar neighborhood stars in our own Galaxy. A by-product of this analysis is a powerful new method for locating the multiple corotation resonances in galaxies (Zhang & Buta 2007; Buta & Zhang 2009).

The current work also highlights the connection between collective effects in galactic dynamics and nonequilibrium phase transition processes in other branches of physics such as fluid turbulence and spontaneous breaking of gauge symmetry in high-energy physics. The continuous build-up of the Hubble sequence of galaxies through secular mass accretion also hints at the baryonic nature of galactic dark matter and poses challenges to the existing LCDM paradigm, since the well-known adiabatic compression process during baryonic mass inflow produced by secular evolution would lead to a concentration of the cold dark matter to the central region of early-type galaxies, which is not observed.
Signatures of long-lived spiral patterns: The color gradient trend
Authors: Martínez-García Eric E. , González-Lópezlira Rosa Amelia
Published: March 2015

Based both on observations and simulations, recent works propose that the speed of the spiral pattern in disk galaxies may decrease with increasing radius; the implications are that patterns are actually short-lived, and that the azimuthal color/age gradients across spiral arms predicted by density wave theory could not be produced. We, however, have consistently found such gradients, and measured spiral pattern speeds by comparing the observations with stellar population synthesis models (González & Graham 1996; Martínez-García et al. 2009a, b; Martínez-García & González-Lópezlira 2011). Here, we summarize our previous results in non-barred and weakly barred spirals, together with six new, as yet unpublished, objects. On the other hand, we have indeed found a trend whereby pattern speeds at smaller radii are larger than expected from a model that assumes purely circular orbits (cf. Figure 1), likely due to the effect of spiral shocks on the orbits of newborn stars. The results suggest that spirals may behave as steady long-lived patterns.
Multiple bars and secular evolution
Authors: Shen Juntai
Published: March 2015

Bars are the most important driver of secular evolution. A significant fraction of barred galaxies also harbor small secondary bars. Secondary bars are visible even in near-infrared images, so they are not just dusty and blue, but stellar features (Erwin & Sparke 2002). Since they are quite common, secondary bars are probably long-lived stellar features. The random relative orientation of the two bars indicates that they are dynamically decoupled with different pattern speeds (Buta & Crocker 1993). Corsini et al. (2003) presented conclusive direct kinematic evidence for a decoupled secondary bar in NGC 2950. Dynamically decoupled secondary bars have long been hypothesized to be a mechanism to drive gas past the ILR of primary bars to feed active galactic nuclei (Shlosman et al. 1989). However, the dynamics of secondary bars are still not well understood, and it is still unclear what role secondary bars play in the AGN fueling process.

Numerical simulations offer the best approach to understanding double-barred systems. Decoupled secondary bar in the earlier gaseous simulations only last a short time (< 1 Gyr, e.g. Friedli & Martinet 1993). Orbital studies of double-barred systems discovered a family of loop orbits that may be building blocks of long-lived nuclear stellar bars (Maciejewski & Sparke 1997, 2000). To complement orbital studies, which are not fully self-consistent, N-body simulations are preferred to further our understanding of double-barred systems. Debattista & Shen (2007) and Shen & Debattista (2009) managed to form long-lived double-barred systems with purely collisionless simulations, where a pre-existing rotating pseudo-bulge is introduced initially. The shape and size of secondary bars in the models are comparable to observed ones. They found that the rotation of the two bars is not rigid. The amplitude and pattern speed of the secondary bars oscillate as they rotate through their primary counterparts. Although the secondary bar rotates faster than the primary bar in this model, the stellar velocity field in the central region only shows a weakly twisted kinematic minor axis.

Recently more simulations of double-barred galaxies with simpler initial conditions are explored (Du, Shen & Debattista 2014). We expect that the new models can be used to cross-check with the kinematic properties of double-barred galaxies from IFU observations such as SAURON and Atlas3D.
Parallel-sequencing of early-type and spiral galaxies
Authors: Cappellari Michele
Published: March 2015

Since Edwin Hubble introduced his famous tuning fork diagram more than 70 years ago, spiral galaxies and early-type galaxies (ETGs) have been regarded as two distinct families. The spirals are characterized by the presence of disks of stars and gas in rapid rotation, while the early-types are gas poor and described as spheroidal systems, with less rotation and often non-axisymmetric shapes. The separation is physically relevant as it implies a distinct path of formation for the two classes of objects. I will give an overview of recent findings, from independent teams, that motivated a radical revision to Hubble's classic view of ETGs. These results imply a much closer link between spiral galaxies and ETGs than generally assumed.
3D view on Virgo and field dwarf elliptical galaxies: late-type origin and environmental transformations
Authors: Ryś Agnieszka , Falcón-Barroso Jesús , van de Ven Glenn
Published: March 2015

In our contribution we show the effects of environmental evolution on cluster and field dwarf elliptical galaxies (dEs), presenting the first large-scale integral-field spectroscopic data for this galaxy class. Our sample con sists of 12 galaxies and no two of them are alike. We find that the level of rotation is not tied to flattening; we observe kinematic twists; we discover large-scale kinematically-decoupled components; we see varying gradient s in line-strength maps: from nearly flat to strongly peaked in the center. The great variety of morphological, kinematic, and stellar population parameters seen in our data supports the claim that dEs are defunct dwarf spiral/irregular galaxies and points to a formation scenario that allows for a stochastic shaping of galaxy properties. The combined influence of ram-pressure stripping and harassment fulfills these requirements, still, the exact impact of the two is not yet understood. We further investigate the properties of our sample by performing a detailed comprehensive analysis of its kinematic, dynamical, and stellar population parameters. The combined knowledge of the dynamical properties and star-formation histories, together with model predictions for different formation mechanisms, will be used to quant itatively determine the actual transformation paths for these galaxies.
Kinematic properties and dark matter fraction of Virgo dwarf early-type galaxies
Authors: Toloba E. , Boselli A. , Peletier R. , Gorgas J.
Published: March 2015

What happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity (Fig. 1). These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older (Fig. 1). Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and the spiral/disky structures of these galaxies. We find that on the the Faber-Jackson and the Fundamental Plane relations dEs deviate from the trends of massive elliptical galaxies towards the position of dark matter dominated systems such as the dwarf spheroidal satellites of the Milky Way and M31. Both, rotationally and pressure supported dEs, however, populate the same region in these diagrams. This indicates that dEs have a non-negligible dark matter fraction within their half light radius.
Vertical structure of stellar populations in galaxy disks
Authors: Streich David , de Jong Roelof S. ,   the GHOSTS team
Published: March 2015

Stellar populations are most useful for disentangling formation and evolution histories of galaxies. We present here results obtained using data from the GHOSTS survey ((Radburn-Smith et al., 2011) which uses HST photometry to resolve stellar populations in nearby massive disk galaxies. Using color magnitude diagrams we can distingiush stellar populations of different ages and analyse the spatial structure of each population seperately.

We have examined the vertical disk structure in six edge-on galaxies. We find a general heating of disk, i.e. larger scaleheights for older populations. The scaleheight of each population is constant over most of radial extent of each galaxy.

In massive galaxies (Vrot > 150 km/s) we clearly see a thick component (i.e. there are more stars at large distances from the plane than expected from a single disk model). These thick components consist of intermediate-aged and old stars (>1 Gyr), and the (thick) scaleheight of the old population (>4 Gyr) is significantly larger than the (thick) scaleheight of the intermediate aged (1-2 Gyr) population.

This finding argues against a rapid formation of the thick components and favors a more secular formation of these components.
Quantifying the mixing due to bars
Authors: Sanchez-Blazquez Patricia
Published: March 2015

We will present star formation histories and the stellar and gaseous metallicity gradients in the disk of a sample of 50 face-on spiral galaxies with and without bars observed with the integral field unit spectrograph PMAS. The final aim is to quantify the redistribution of mass and angular momentum in the galactic disks due to bars by comparing both the gas-phase and star-phase metallicity gradients on the disk of barred and non-barred galaxies. Numerical simulations have shown that strong gravitational torque by non-axisymmetric components induce evolutionary processes such as redistribution of mass and angular momentum in the galactic disks (Sellwood & Binney 2002) and consequent change of chemical abundance profiles. If we hope to understand chemical evolution gradients and their evolution we must understand the secular processes and re-arrangement of material by non-axisymmetric components and vice-versa. Furthermore, the re-arrangement of stellar disk material influences the interpretation of various critical observed metrics of Galaxy evolution, including the age-metallicity relation in the solar neighborhood and the local G-dwarf metallicity distribution. Perhaps the most obvious of these aforementioned non-axisymmetric components are bars - at least 2/3 of spiral galaxies host a bar, and possibly all disk galaxies have hosted a bar at some point in their evolution. While observationally it has been found that barred galaxies have shallower gas-phase metallicity gradients than non-barred galaxies, a complementary analysis of the stellar abundance profiles has not yet been undertaken. This is unfortunate because the study of both gas and stars is important in providing a complete picture, as the two components undergo (and suffer from) very different evolutionary processes.
What Disc Brightness Profiles Can Tell us about Galaxy Evolution
Authors: Beckman John , Erwin Peter , Gutiérrez Leonel
Published: March 2015

Azimuthally averaged surface brightness profiles of disc galaxies provide a most useful practical classification scheme which gives insights into their evolution. Freeman (1970) first classified disc profiles into Type I, with a single exponential decline in surface brightness, and Type II, having a split exponential profile, whose inner radial portion is shallower than its outer section. Van der Kruit & and Searle, (1981) drew attention to sharply truncated profiles of outer discs observed edge-on, but more recently Pohlen et al. (2004) showed that if these same galaxies were observed face-on their profiles would be of Type II. Finally in Erwin, Beckman and Pohlen (2005) we found a significant fraction of profiles with inner portion steeper than the outer portion, which we termed “antitruncations“ or Type III profiles. In Erwin, Pohlen and Beckman (2008), we produced a refined classification, taking into account those Type II's produced by dynamical effects at the outer Lindblad resonance, and those Type III's caused by the presence of an outer stellar halo. In Gutiérrez et al. (2011) we showed the distribution of the three main profile types along the Hubble sequence. In early type discs Types I and III predominate, while in late types, Sc and later, Type II predominates.

The evolution of Type II's over cosmic time was studied by Azzollini et al. (2008a, 2008b) who obtained four key results: (a) between z = 1 and z = 0 the break radius between the inner (shallower) and outer (steeper) profile has increased systematically, by a factor 1.3; (b) the inner profile has steepened while the outer profile is shallower at lower z; (c) the extrapolated central surface brightness has fallen by over two magnitudes; (d) the discs in the full redshift interval are always bluest at the break radius. While this behaviour can be qualitatively explained via evolutionary models including stellar migration plus gas infall, such as that by Roskar et al. (2008), and while Type III profiles may have a qualitative explanation via mergers and/or accretion, the widespread existence of Type I's is still a major conceptual challenge.
The role of close pair interactions in triggering stellar bars and rings
Authors: Nair Preethi , Ellison Sara , Patton David
Published: March 2015

Recent works which have looked at bars in clusters versus the field have found no significant difference in bar fraction. However, other works (Nair & Abraham 2010, Lee et al.2012) have found that bar fractions depend sensitively on the mass, morphology and color of the galaxy. In addition, simulations suggest that bar formation may depend on the merger ratio of close pair interactions as well as on the separation between the pairs. In this work, we analyze the bar fractions in a complete sample of ≈23,000 close pairs derived from the Sloan Digital Sky Survey Data Release 7. We will present results illustrating the dependence of bar and ring fractions as a function of merger mass ratio, pair separation, galaxy morphology, and stellar mass. I will further compare the role of bars and close pairs in triggering central star formation and AGN.
Intense velocity-shears, magnetic fields and filaments in diffuse gas
Authors: Falgarone Edith , Hily-Blant Pierre , Levrier François , Berthet Manuel , Bastien Pierre , Clemens Dan
Published: March 2015

The dissipation of turbulence is a key process in the evolution of diffuse gas towards denser structures. The vast range of coupled scales and the variety of dissipative processes in interstellar turbulence make it a complex system to analyze. Observations now provide powerful statistics of the gas velocity field, density and magnetic field orientations, opening a rich field of investigation. On-going comparisons of the orientation of intense velocity-shears, magnetic field and tenuous filaments of matter in a turbulent high-latitude cloud are promising.
Effects of Magnetic Fields on Bar Substructures in Barred Galaxies
Authors: Kim Woong-Tae
Published: March 2015

To study the effects of magnetic fields on the properties of bar substructures, we run two-dimensional, ideal MHD simulations of barred galaxies under the influence of a non-axisymmetric bar potential. In the bar regions, magnetic fields reduce density compression in the dust-lane shocks, while removing angular momentum further from the gas at the shocks. This evidently results in a smaller and more distributed ring, and a larger mass inflows rate to the galaxy center in models with stronger magnetic fields. In the outer regions, an MHD dynamo due to the combined action of the bar potential and background shear operates, amplifying magnetic fields near the corotation resonance. In the absence of spiral arms, the amplified fields naturally shape into trailing magnetic arms with strong fields and low density. The reader is refereed to Kim & Stone (2012) for a detailed presentation of the simulation outcomes.
Magnetic Field Structure in Molecular Clouds by Polarization Measurements
Authors: Chen W. P. , Su B. H. , Eswaraiah C. , Pandey A. K. , Wang C. W. , Lai S. P. , Tamura M. , Sato S.
Published: March 2015

We report on a program to delineate magnetic field structure inside molecular clouds by optical and infrared polarization observations. An ordered magnetic field inside a dense cloud may efficiently align the spinning dust grains to cause a detectable level of optical and near-infrared polarization of otherwise unpolarized background starlight due to dichroic extinction. The near-infrared polarization data were taken by SIRPOL mounted on IRSF in SAAO. Here we present the SIRPOL results in RCW 57, for which the magnetic field is oriented along the cloud filaments, and in Carina Nebula, for which no intrinsic polarization is detected in the turbulent environment. We further describe TRIPOL, a compact and efficient polarimer to acquire polarized images simultaneously at g', r', and i' bands, which is recently developed at Nagoya University for adaption to small-aperture telescopes. We show how optical observations probe the translucent outer parts of a cloud, and when combining with infrared observations probing the dense parts, and with millimeter and submillimeter observations to sutdy the central embedded protostar, if there is one, would yield the magnetic field structure on different length scales in the star-formation process.
Magnetic Fields in the Milky Way Halo
Authors: Mao S. A. , McClure-Griffiths N. M. , Gaensler B. M. , Brown J. C. , van Eck C. L. , Haverkorn M. , Kronberg P. P. , Stil J. M. , Shukurov A. , Taylor A. R.
Published: March 2015

We present a study of the Milky Way halo magnetic field, determined from observations of Faraday rotation measure (RM) of extragalactic radio sources (EGS) in Galactic longitude range 100°–117° within 30° of the Galactic plane. We find negative median RMs in both the northern and southern Galactic hemispheres for |b|>15°, outside the latitude range where the disk field dominates. This suggest that the halo magnetic field towards the outer Galaxy does not reverse direction across the mid-plane. An azimuthal magnetic field at heights 0.8−2 kpc above/below the Galactic plane between the local and the Perseus spiral arm can reproduce the observed trend of RM against Galactic latitude. We propose that the Milky Way could have a halo magnetic field similar to that observed in M51.
Observations of magnetic fields in intracluster medium
Authors: Govoni Federica
Published: March 2015

The presence of μG-level magnetic fields associated with the intracluster medium of galaxy clusters is now widely acknowledged. Our knowledge of their properties has greatly improved in the recent years thanks to both new radio observations and the developments of new techniques to interpret data.
Near Earth Objects Research in Pulkovo Observatory
Authors: Devyatkin A. V. , Bashakova E. A. , Gorshanov D. L. , Ivanov A. V. , Karashevich S. V. , Kouprianov V. V. , L'vov V. N. , Naumov K. N. , Romas E. S. , Slesarenko V. Yu. , Shakht N. A. , Sokov E. N. , Tsekmeister S. D. , Vasilkova O. O. , Vereschagina I. A.
Published: March 2015

More than 20000 observations of Near Earth asteroids and comets are collected and reduced in Pulkovo Observatory during last 10 years. For observations of these objects two robotic telescopes are used – ZA-320M (Cassegrain system, D = 320 mm, F = 3200 mm) at Pulkovo and MTM-500M (Maksutov – Cassegrain system, D = 500 mm, F = 4100 mm) at Kislovodsk mountain station. These telescopes perform CCD observations of objects up to 18.0 and 20.5 magnitude, correspondingly. The results of observations are regularly submitted to Minor Planet Center.
AIDA: Asteroid Impact and Deflection Assessment
Authors: Michel Patrick , Cheng A. , Galvez A. , Reed C. , Carnelli I. , Abell P. , Ulamec S. , Rivkin A. , Biele J. , Murdoch N.
Published: March 2015

AIDA (Asteroid Impact and Deflection Assessment) is a project of a joint mission demonstration of asteroid deflection and characterisation of the kinetic impact effects. It involves the Johns Hopkins Applied Physics Laboratory (with support from members of NASA centers including Goddard Space Flight Center, Johnson Space Center, and the Jet Propulsion Laboratory), and the European Space Agency (with support from members of the french CNRS/Cte dAzur Observatory and the german DLR). This assessment will be done using a binary asteroid target. AIDA consists of two independent but mutually supporting mission concepts, one of which is the asteroid kinetic impactor and the other is the characterisation spacecraft. The objective and status of the project will be presented.
Using Astronomy to shape a country's science and technology landscape
Authors: Mokhele Khotso
Published: March 2015

There is data abundant to show a positive correlation between a nation's investment in science, engineering and technology and the economic prosperity of that nation. Yet, there remain many countries in the world, particularly in developing countries, where little, if any, serious investment in science, engineering and technology is evident. Even in these countries, policy documents speak positively about the positive correlation between investment in science, engineering and technology and national development and prosperity. Unfortunately these positive policy statements rarely get converted into real investment. When the National Research Foundation was founded in Post-Apartheid South Africa it set out to “. . .contribute to the improvement of the quality of life of all people. . .” and its inspiring vision was to achieve “A prosperous South Africa and African continent steeped in a knowledge culture, free of widespread diseases and poverty, and proud contributors to the well-being of humanity." This organisation, with its altruistic vision, succeeded in convincing the emerging government to invest in and support the construction of the Southern African Large Telescope as one of its flagship projects. This decision was subsequently followed by a high level national decision to leverage South Africa's geographical advantage to host major global astronomy facilities such as the Square Kilometer Array. This presentation highlighted the reasons for such decisions and how we went about motivating government organs that investing in astronomy would contribute to addressing societal challenges by stimulating the science and technology landscape.
Status of astronomy in Rwanda and volunteer work at Kigali Institute of Education (KIE)
Authors: Pović M. , Nkundabakura P. , Uwamahoro J.
Published: March 2015

Until 2009, astronomy was undeveloped in Rwanda, without astronomy courses at universities and schools, astronomical facilities, or any outreach programmes. With the international year of astronomy in 2009, Dr. Pheneas Nkundabakura and Dr. Jean Uwamahoro from the KIE Maths-Physics department, both graduates from the South African NASSP Programme (http://www.star.ac.za), started a program of implementing the astronomical knowledge at schools and universities. During the same year 2009, IAU donated 100 galileoscopes for the secondary schools, and several astronomy workshops were organised for the teachers. IAU donated also 5 laptops to help students and lecturers to learn and use astronomy software. With this, KIE students have now a possibility to choose astronomy/space science for their undergraduate final year research projects. Moreover, there is an ongoing effort to look for further collaboration towards establishing the first astronomical facility (observatory) in the country.
Education for development under the skies of Chile
Authors: Scorza Cecilia , Fischer Olaf
Published: March 2015

We report on an educational program initiated in Chile in the year 2010 on the frame of an excellence research and graduate exchange program between the University of Heidelberg and the Pontfica Catlica University in Chile, funded by the German International Exchange Office (DAAD).
Touch the sky with your hands: a special Planetarium for blind, deaf, and motor disabled
Authors: García Beatriz , Maya Javier , Mancilla Alexis , Álvarez Silvina Pérez , Videla Mariela , Yelós Diana , Cancio Angel
Published: March 2015

The Planetarium for the blind, deaf, and motor disabled is part of the program on Astronomy and Inclusion of the Argentina Pierre Auger Foundation (FOPAA) and the Institute in Technologies and Detection of Astroparticles-Mendoza (ITeDAM).
The pre-modern era of the ISM
Authors: Dickey John M.
Published: March 2015

The history of our understanding of the interstellar medium has a pre-modern era and an early-modern era. Several threads show continuity in observational approach and interpretation, reaching from the first decade of the last century to the present. The first 50 years were a period of pioneering work, done mostly by stellar astronomers, who chanced upon the ISM by a strange variety of pathways.
On the origins of the diffuse Hα emission: ionized gas or dust-scattered Hα halos?
Authors: Seon Kwang-Il , Witt Adolf N.
Published: March 2015

We find that the dust-scattering origin of the diffuse Hα emission cannot be ruled out. As opposed to the previous contention, the expected dust-scattered Hα halos surrounding H II regions are, in fact, in good agreement with the observed Hα morphology. We calculate an extensive set of photoionization models by varying elemental abundances, ionizing stellar types, and clumpiness of the interstellar medium (ISM) and find that the observed line ratios of [S II]/Hα, [N II]/Hα, and He I λ5876/Hα in the diffuse ISM accord well with the dust-scattered halos around H II regions, which are photoionized by late O- and/or early B-type stars. We also demonstrate that the Hα absorption feature in the underlying continuum from the dust-scattered starlight (“diffuse galactic light”) and unresolved stars is able to substantially increase the [S II]/Hα and [N II]/Hα line ratios in the diffuse ISM.
Stability properties of phase transition layers in the diffuse ISM revisited
Authors: Stone Jennifer M. , Inutsuka Shu-ichiro , Zweibel Ellen G.
Published: March 2015

In a thermally bistable medium, cold, dense gas is separated from warm, rarified gas by thin phase transition layers, or fronts, in which radiative heating/cooling, thermal conduction, and convection of material are balanced. While these fronts have received only scant attention in the literature, and are not resolved by most current numerical simulations, they have been shown to have important ramifications for transport processes and structure formation in the diffuse interstellar medium. Here, we discuss calculations of their hydrodynamic and magnetohydrodynamic stability properties.
Dust emission from the atomic and molecular gas in M 33: a changing β
Authors: Braine Jonathan , Tabatabaei Fatemeh , Xilouris Manolis
Published: March 2015

We use the very recently completed high-resolution IRAM CO survey of M33 with the high-resolution HI observations (published by Gratier et al. 2010, A&A, 522, 3) and Herschel Far-IR and submillimeter mapping observations to study how the dust behaves in the molecular and atomic gas phases of the interstellar medium (ISM). M33 is a “young" object in that it is gas-rich with a young stellar population and low metallicity as compared to large spirals like the Milky Way or Andromeda. Nonetheless, it is very clearly a spiral galaxy with a thin and reasonably axisymmetric disk. As such, it can be viewed as a stepping stone towards less evolved objects like magellanic irregulars (including the LMC and SMC) and perhaps distant objects in the early universe. More specifically, we look for radial variations in the dust emission spectrum (β parameter) as well as comparing regions dominated by either H2 or HI. The grey-body emission spectrum flattens (lower β) with galactocentric distance and generally is flatter in the atomic medium as compared to the molecular gas.