The Smooth Particle Hydrodynamics (SPH) impact code (Benz & Asphaug 1994) has been developed for the simulation of impacts and collisions involving brittle solids in the strength-and gravity-dominated regime. In the latter regime, the gravitational overburden is used to increase the fracture threshold. In this paper, we extend our numerical approach to include the effect of porosity at a sub-resolution scale by adapting the so-called P -α model (Herrman 1969). Using our extended 3D SPH impact code, we investigated collisions between porous bodies to examine the sensitivity of collisional outcomes to the degree of porosity. Two applications that illustrate the capabilities of our approach are shown: 1) the modeling of a Deep Impact-like impact and 2) the computation of the amount of momentum transferred to an asteroid following the impact of a high velocity projectile.

We studied the stability properties of isolated star forming dwarf galaxies with the aim to identify star burst modes. The impact of the stellar birth function (parametrization, IMF), the stellar feedback and the ISM model on the galactic star formation history was investigated. We focussed especially on dynamically driven star bursts induced by stellar feedback. We applied a one-zone model for a star-gas system coupled by both mass and energy transfer. Additionally, we extended the classical closed box network for active dynamical evolution (Theis 2004). This allows for a simple, but consistent description of the coupling between the dynamical state of a galaxy and its internal properties like star formation activity or the thermal state of the interstellar medium.

Helioseismology has provided robust estimates of global properties of the solar convection zone, its depth, stratification, and revealed rotational shear layers at the boundaries. New methods of local helioseismology provide 3D maps of subsurface convective flows. In the quiet Sun regions, these maps reveal that supergranular-scale convection extends to the depth of 12–15 Mm. Analysis of evolution of the supergranular convection pattern shows evidence for a wave-like behavior which might be related to the interaction between convection and the subsurface rotational sheer layer. Helioseismology also reveals large-scale circulation flows around magnetic regions. These flows affect the evolution of the mean meridional flow during the solar cycle and, probably, the magnetic flux transport from mid-latitudes to the polar regions, a process important for solar dynamo theories. Helioseismic measurements on a smaller scale, below sunspots, give insight on how convection interacts with strong magnetic fields.

Some of the problems related to Near Earth Objects (NEOs), like orbit determination and ephemeris computation, are not new, and had to be dealt with since the beginning of NEO astronomy. The latter practically started with the discovery of Comet D/1770 L1 Lexell, that passed very close to the Earth in 1770; studies of the chaotic dynamics of this exceptional object continued well into the XIXth century. At the end of the XXth century there has been a renewal of interest in NEOs, as attested by IAU Symposium 236.

Beginning in 2001, the Gemini Observatory began the development of an innovative and aggressive education and outreach programme at its southern hemisphere site in northern Chile. A principal focus of this effort is centered on local education and outreach to communities surrounding the observatory and its base facility in La Serena, Chile. Programmes are now established with local schools using two portable StarLab planetaria, an internet-based teacher exchange called StarTeachers and multiple partnerships with local educational institutions. Other elements include a CD-ROM-based virtual tour that allows students, teachers and the public to experience the observatory's sites in Chile and Hawaii. This virtual environment allows interaction using a variety of immersive scenarios such as a simulated observation using real data from Gemini. Pilot projects like “Live from Gemini” are currently being developed which use internet video-conferencing technologies to bring the observatory's facilities into classrooms at universities and remote institutions. Lessons learned from the implementation of these and other programmes will be introduced and the challenges of developing educational programming in a developing country will be shared.

Asteroseismology—using stellar oscillations to study the interiors of stars—is a relatively new and growing research field in astrophysics. Oscillations are found in stars of most masses and essentially all stages of evolution. Their frequencies are determined by the internal sound speed and density structure of the star, as well as rotation, convection processes and possibly effects of magnetic fields. Recent developments have led to a breakthrough in our ability to study the details of cores of solar-like stars and it is foreseen that a number of key science questions will be addressed through the analysis of frequencies and other properties of stellar oscillations. In this paper we review some of the latest results from asteroseismology of solar-like stars, with the focus on properties of convection.

We use a set of hydrodynamical, self consistent simulations operating in the context of a concordance cosmological model where relaxed elliptical-like objects (ELOs) were identified at different redshifts. ELOs at different redshift are well described by the Sérsic (1968) function. We also obtain a good comparison with observational scaling relations. These results indicate that ELOs conform a homogeneous population at any redshift, except that high z ELOs tend to be more compact that their lower z counterparts. Also, scaling relations point to the rupture of the structural homology.

We study (i.e., Dib et al. 2006) the virial balance of clumps and cores (CCs) in a set of three-dimensional numerical simulations of driven, magnetohydrodynamical, isothermal molecular clouds (MCs). The simulations represent a range of magnetic field strengths in MCs from subcritical to non-magnetic regimes. We developed a clump-finding algorithm to identify CCs at different threshold levels in the simulation box, and for each object, we calculate all the terms that enter the virial theorem in its Eulerian form. We also calculate, other quantities commonly used to indicate the state of gravitational boundedness of CCs such as the Jeans number Jc, the mass-to magnetic flux ratio μc, and the virial parameter αvir. Our results suggest that a) CCs are dynamical out-of-equilibrium structures. b) The surface energies are of the same order than their volume counterparts and thus are very important in determining the exact energy balance in CCs. c) CCs can be either in the process of being compressed by the velocity field or of being dispersed. Yet, not all CCs that have a compressive velocity field at their boundaries are necessarily gravitationally bound. d) There is no one-to-one correspondence between the state of gravitational boundedness of a CC as described by the energy balance analysis (i.e., gravity versus other energies) or as implied by the classical indicators Jc, μc, and αvir. In general, from the energy analysis, we observe that only the inner regions of the objects (i.e., the dense cores selected at high threshold levels) are gravitationally bound, whereas Jc and αvir estimates tend to show that they are more gravitationally bound at the lowest threshold levels. g) We observe, in the non-magnetic simulation, the existence of a bound core with structural and dynamical properties that resemble those of the Bok globule Barnard 68 (B68). This suggests that B68 like cores can form in a larger molecular cloud and then be confined by the warm gas of a newly formed HII region, which can heat and rarefy the gas around the core, confine it, and extend its lifetime.

We study magnetohydrodynamic (MHD) standing shocks in ingoing plasmas in a black hole (BH) magnetosphere. We find that low or mid latitude (non-equatorial) standing MHD shocks are both physically possible, creating very hot and/or magnetized plasma regions close to the event horizon. We also investigate the effects of the poloidal magnetic field and the BH spin on the properties of shocks and show that both effects can quantitatively affect the MHD shock solutions. MHD shock formation can be a plausible mechanism for creating high energy radiation region above an accretion disk in AGNs.

The relative positions of Hipparcos visual double star components are currently known with a precision around fifty mas. Modern CCD astrometric observations of these objects achieve an accuracy of their angular separation between ten and twenty mas per observation. New CCD measurements have been obtained at Kryonerion Observatory in the north hemisphere. They provide current relative positions of visual double stars which are at least twice as accurate as the ones provided by Hipparcos. The new measurements will permit us to extract the physical pairs from the sample, and the double stars, which have components of common origin. Final statistics of these systems will improve our understanding of stellar formation and evolution rates of wide binaries in the solar neighborhood.

I discuss current observational constraints on the star-formation and stellar-assembly histories of galaxies at high redshifts. The data on massive galaxies at z < 1 implies that their stellar populations formed at z>2, and that their morphological configuration was in place soon thereafter. Spitzer Space Telescope 24 μ observations indicate that a substantial fraction of massive galaxies at z ~ 1.5–3 have high IR luminosities, suggesting they are rapidly forming stars, accreting material onto supermassive black holes, or both. I compare how observations of these IR–active phases in the histories of massive galaxies constrain current galaxy–formation models.

I review the current status of stellar population modelling, with particular emphasis on the treatment of the Thermally-Pulsing Asymptotic Giant Branch stellar phase. I discuss how much the physical properties of galaxies that are derived applying these models to real data, depend on the adopted model.

Blue stragglers stars (BSS) define a sparsely populated sequence extending to higher luminosity than the turnoff point of normal main sequence stars in the color magnitude diagrams of stellar aggregates, thus mimicking a rejuvenated (more massive) stellar population. The nature of these stars has been a puzzle for many years and their formation mechanism is not completely understood, yet. Two mechanisms have been proposed to produce BSS: (i) the mass transfer in binary systems; and ((ii) the merger of two stars induced by stellar interactions. In this contribution we schematically report on the main properties of BSS in globular clusters (GCs) in the light of the most recent photometric and spectroscopic observations. These results, combined with dynamical simulations, indicate that both the proposed formation mechanisms play an important role in the production of BSS in GCs.

While the existence of cycles in stellar chromospheric flux has been known for some time, the nature of the corresponding coronal response has been more elusive. We describe recent results on the relationship between cyclic variations in surface magnetic flux and coronal structure and re-assess the role of prominence observations in understanding the topology of stellar coronas. We present a new paradigm for prominence support which allows for extended prominences to co-exist with a compact corona. We discuss briefly the recent results on coronal structure in high- and low-mass stars and their implications for dynamo theory.

The advent of larger telescopes and powerful instrumentation enables the exploration of new aspects of faint eclipsing binaries that are just now becoming accessible. An example of this are eclipsing binaries in Local Group galaxies such as the LMC, SMC, M31 and M33, whose study yields not only stellar properties of stars formed in different chemical environments (thus providing useful model tests) but also direct distance determinations to the host galaxies. In general this is also applicable to eclipsing binaries belonging to any stellar ensemble. Another example is the observation and study of eclipsing very-low mass stars, brown dwarfs and planets. Besides the need for large telescopes because of their faintness, these also benefit from improved observational capabilities in the infrared spectral windows. Here we discuss the prospects for eclipsing binary research using photometry and spectroscopy from large telescopes.

We review some of the extensive historical observations of SN 1006, emphasizing estimates of its brightness at maximum. An estimate of Vmax ≈ −7.5 is consistent with what may be the most reasonable interpretation of these records and with an a posteriori calculation based on typical peak magnitudes for Type Ia supernovae together with the distance and extinction to SN 1006. We also give a brief overview of the discovery of the SN 1006 remnant in 1965, and contrast the earliest radio, optical, and X-ray observations of the remnant with recent ones, as reported in more detail by other papers in this JD09 review.

We construct a model of the physical structure of photoevaporating protoplanetary disks, and numerically calculate the coagulation and settling/evaporating process of dust particles in the disks. Our result show that (sub)micron-sized-dust-particles could evaporate with the gas, which leads to dispersal of infrared excess radiation from the disks.

The polar magnetic fields on the Sun have been an attractive subject for solar researches since Babcock measured them in solar cycle 19. One of the remarkable features of the polar magnetic fields is their reversal during the maxima of 11-year sunspot cycles. I have present results of the investigations of the polar magnetic field using SOHO-mdi data. It is found, that the polar magnetic field reversal is detected with mdi data for polar region within 78°–88°. The North Pole has changed polarity in CR1975 (April 2001). The South reversed later in CR1980 (September 2001). The total unsigned magnetic flux does not show the dramatic decreasing during the polar reversals due to omnipresent bi-polar small-scale magnetic elements. The observational and theoretical aspects of the polar magnetic field reversals are discussed.

We study subhalo populations surrounding massive dark matter haloes by using three AMIGA simulations each having different mass and spatial resolutions. Our analysis shows that the slope of the subhalo mass function has a value 0.9, which agrees with previous studies. The dependence of mass functions on redshift is the same for subhaloes and main haloes. In all simulations, combined subhalo masses are about 0.1-0.2 of main halo masses and this mass fraction increases slightly with redshift and the mass of the main halo. The distribution of mass fractions for subhaloes is close to Gaussian at z = 0 and differs slightly at earlier epochs. Spatial distribution of subhaloes as measured in units of virial radius Rvir of the main halo does not depend on redshift and follows r1/3 rule. Spatial distribution of all haloes surrounding main haloes continues up to 3 times Rvir with equal slope but lower amplitude. Beyond 16 times Rvir, the average distribution of haloes becomes uniform.