We discuss the selection of star-forming galaxies at z≃6 through the Lyman-break technique. Spitzer imaging implies many of these contain older stellar populations (>200Myr) which produce detectable Balmer breaks. The ages and stellar masses (∼1010M⊙) imply that the star formation rate density at earlier epochs may have been significantly higher than at z≃6, and might have played a key role in re-ionizing the universe.

We review recent pilot simulations that incorporate feedback from ionising radiation in SPH calculations of star forming clouds. In the case that the ionising radiation source is located within the star forming cloud, the inhomogeneity of the cloud significantly modifies the way that feedback operates compared with spherically symmetric cloud models. Inflow/outflow behaviour develops, combining accretion down dense filaments and thermally driven outflows that can remove many times the binding energy of the parent cloud. If the ionising source is located external to the cloud, we find evidence for triggered star formation but conclude that it is hard to find unambiguous observational signatures that would distinguish “triggered” stars from those created spontaneously.

Our knowledge about unresolved stellar systems comes from comparing integrated-light properties to SSP models. Therefore it is crucial to calibrate the latter as well as possible by integrated-light colors of clusters that have reliable ages and metallicities (deep CMDs and/or spectroscopy of individual giants). This is especially true for the NIR and MIR, which contain important population synthesis diagnostics and are often used to derive masses of stellar systems at hight redshifts. Here we present integrated colors of MC clusters using new VRI photometry and 2MASS data. In the imminent future we will include MIR data from Spitzer/IRAC. We compare our new colors with popular SSP models to illustrate their strengths and weaknesses.

Comets account for a small but very significant fraction of impactors on the Earth. Although the total number of Earth-crossing comets is modest as compared with asteroids, the more eccentric and inclined orbits of the comets result in much higher encounter velocities with the planet. Additionally, some Earth-crossing comets are significantly larger than any current near-Earth asteroids (NEAs); comets 1P/Halley and C/1995 O1 Hale-Bopp are good examples of this. Thus, the most energetic impacts on the Earth likely result from comets and not NEAs. The mean impact probability for long-period comets is 2.4× 10−9 per comet per perihelion passage, assuming the perihelion distribution of Everhart (1967), with a most probable encounter velocity of 53.5 km sec−1. There are 21 known Earth-crossing Jupiter-family comets with a mean impact probability of 1.6× 10−9 per comet per year and a most probable encounter velocity of 17.0 km sec−1. For the 16 known Earth-crossing Halley-type comets the mean impact probability is 1.2× 10−10 per year with a most probable encounter velocity of 51.3 km sec−1. The poor knowledge of the size distribution of cometary nuclei makes it difficult to estimate actual impact energies at this time, though that situation is slowly improving, in particular for the Jupiter-family comets.

Ellerman bombs or moustache are known as short-living fine emission structures associated with a local energy release in solar atmosphere. The relation between the moustaches and flare has been discussed since the moment of the moustaches discovery. The resent results of the Flare Genesis Experiment demonstrated that this problem is still actual and attractive. We took into account the possibility of different mechanisms of their origin (thermal and non-thermal) by using spectro polarimetric data obtained in summer 1999 and carried out analysis of Ellerman bomb's role in flare activity of the Sun by the example of the several active regions.

Using anisotropic Fokker-Planck models, we calculate the evolution of mass and luminosity functions of the Galactic globular cluster system. Our models include two-body relaxation, binary heating, tidal shocks, dynamical friction, and stellar evolution. We perform Fokker-Planck simulations for a large number of virtual globular clusters and synthesize these results to study the relation between the initial and present GCMFs.

Planetary nebulae (PNe) have the potential to revolutionize our understanding of extragalactic stellar populations. Indeed, in many systems, bright PNe are the only individual objects identifiable from the ground, and, even more often, they are the only stars that are amenable to spectroscopy. We review the ways in which ensembles of PNe can be used to probe the metallicity, age, and history of a stellar population. In particular, we discuss three cases: the weak line spectroscopic regime, where one has knowledge of the line-strengths of faint forbidden lines such as [O III] $\lambda 4363$, a bright-line regime, where only the strongest emission lines are visible, and the photometric regime, where the only information available is the [O III] $\lambda 5007$ luminosity function. We show that each of these cases, when properly calibrated, can provide unique insights into the objects that make up a stellar population.

The Committee on Space Research (COSPAR) Capacity-Building Programme introduces astronomers in the developing world to the rich resource of space research online archives. The programme consists of a series of regional workshops which each bring together about 30 developing world astronomers with around 8 teaching faculty for lectures and hands-on projects. Five workshops have been held so far with another two planned for next year and a budget which enables on average one workshop each year. Proposals for future workshops are encouraged.

I argue that binary star statistics offer the best observational constraints on current hydrodynamical simulations of star forming clusters. In these simulations, clusters form hierarchically from the bottom up, and dynamical interactions, mediated by the presence of circumstellar material, play a vital role at the lowest (few body) level of the hierarchy. Such a scenario produces a rich array of complex multiple systems whose properties are in many respects consistent with observations. I however highlight two areas of current disagreement: the simulations over-produce low mass single stars and under-produce binaries with low mass ratios. It is currently unclear to what extent these shortcomings reflect numerical issues and to what extent the omission of relevant physical processes. I conclude with a theorist's wish list for observational diagnostics that would most meaningfully constrain future modeling efforts.

A remarkable and intriguing fact is that few DB white dwarfs, i.e., objects with a helium-rich atmosphere, are found in the effective temperature range between 45000-30000 K, and this exclusion zone is known as the DB gap. Since the temperatures of the blue and the red edges of the DB gap coincide with the effective temperatures where HeII/III and HeI/II convection zones show up respectively, convective mixing is suspected to be the cause of the appearance of DBs outside the DB gap. Chemical separation due to gravitational settling in the convectively stable atmosphere is then suspected to be the cause of the presence of the DB gap. The white dwarfs which turn back to DBs after the DB gap phase are expected to have a semiconvective layer, which is superadiabatic but convectively stable, when they are located near the red edge of the DB gap. Such white dwarfs are expected to be pulsationally unstable. Discovery of pulsation in them will open up a new class of pulsating white dwarfs to asteroseismic study.

We describe an observation designed to find Hα emission from galaxies at z≃7–12 made using the InfraRed spectrograph (IRS) on the Spitzer Space Telescope.

We have obtained the first accurate determination of the albedo of (99942) Apophis, by means of polarimetric observations carried out at the VLT. The observations allowed us to obtain the slope of the polarization–phase curve of this object, from which an albedo estimate of 0.33 ± 0.04 could be obtained. From our observations we also obtained a new estimate of the absolute magnitude: H = 19.7 ± 0.2 (assuming G=0.25, which applies to S- and Q-type asteroids). Based on these results, we derive for the size of Apophis a value of 270 ± 30 meters. The accuracy of this size estimate is mostly related to uncertainties in H, whereas the obtained albedo value should be considered more robust. Our observations convincingly show that polarimetry is an effective and efficient tool to obtain accurate albedos and sizes for small and faint potentially hazardous asteroids.

We analyze time series scans of the solar limb performed by the spectrometer SUMER on-board the SoHO satellite. The analyzed dataset consists of observations obtained in the C III 977 Å line. After applying the standard SUMER data reduction procedure, we perform a one line Gaussian fit to the profiles to obtain different parameters for each pixel within the scans. Studying the variations of the line width from the disk to the limb and off-limb we find that it increases off-limb and shows a peak at $\sim15\prime\prime above the limb. We suggest that this increase is due to the random directions of several spicules found along the line of sight.

We show that in a sample of Extremely Metal-Poor (EMP) giants (<[Fe/H]>=−3.1) all the stars with a luminosity higher than logL/L⊙ ≈ 2.6 present the characteristics of a mixing of the surface with the H-burning layer: low abundance of carbon and high abundance of nitrogen. In these “mixed stars” the lithium abundance and the ratio 12C/13C are very low. Some of these stars are also Na or/and Al rich.

While until recently they were often considered as exotic objects of dubious existence, in the last decades there have been overwhelming observational evidences for the presence of stellar mass black holes in binary systems, supermassive black holes at the centers of galaxies, and possibly, intermediate-mass black holes observed as ultraluminous X-ray sources in nearby galaxies. Black holes are now widely accepted as real physical entities that play an important role in several areas of modern astrophysics.

Here I review the concluding remarks of the IAU Symposium No 238 on Black Holes, with particular emphasis on the topical questions in this area of research.

We attempt to provide new insights into the kinematics of narrow-line regions (NLR) in Seyfert galaxies and quasars, the understanding of which, as well as of their intrinsic 3D morphology, is still rather limited. Motivated by the rise of the integral-field spectroscopy, capable of mapping full 2D velocity fields, and by our observational projects on NLRs (see e.g. Stoklasová et al., this volume) we have developed a computer code producing 2D kinematical maps resulting from projections of various gas geometries and velocity fields.

We perform 3D MHD simulations of cluster formation in turbulent magnetized dense molecular clumps, taking into account the effect of protostellar outflows. Our simulation shows that initial interstellar turbulence decays quickly as several authors already pointed out. When stars form, protostellar outflows generate and maintain supersonic turbulence that have a power-law energy spectrum of Ek ~ k−2, which is somewhat steeper than those of driven MHD turbulence simulations. Protostellar outflows suppress global star formation, although they can sometimes trigger local star formation by dynamical compression of pre-existing cores. Magnetic field retards star formation by slowing down overall contraction. Interplay of protostellar outflows and magnetic field generates large-amplitude Alfven and MHD waves that transform outflow motions into turbulent motions efficiently. Cluster forming clumps tend to be in dynamical equilibrium mainly due to dynamical support by protostellar outflow-driven turbulence (hereafter, protostellar turbulence).

Planetary Nebula (PN) shells and AGB circumstellar envelopes evolve under a wide range of external conditions, from the high ISM densities found in the Galactic plane, to the rarefied and hot intracluster medium where the systemic velocity of the star can be as high as 2000 km $s^{-1}$. We explore the effects that the external pressure and/or stellar systemic velocity have on the observable properties of PNe. We investigate how the mass and size of the PN halos are reduced when the star is moving with respect to the external medium. We have studied as well how the mass of the circumstellar envelope is fed by ISM material when high ISM densities characteristic of the Galactic plane are considered. By studying the evolution of PNe in the intracluster medium in Virgo, we infer shorter PN lifetimes than what is usually adopted. This has important implications, since the assumed PN lifetime strongly affects the fraction of intracluster light derived from PN studies.

We consider the multiplicity of stellar systems with (combined) magnitude brighter than 6.00 in Hipparcos magnitudes. We identify 4555 such bright systems, and the frequencies of multiplicities 1, 2, . . , 7 are found to be 2722, 1412, 299, 86, 22, 12 and 2. We also consider the distributions of periods of orbits and sub-orbits. For the even more restricted set of 474 systems with VH ≤ 4.00 the proportions of higher multiples up to sextuple are progressively larger, suggesting incompleteness in even the relatively well-studied larger sample.

We construct a Monte-Carlo algorithm that will generate systems with roughly the observed multiplicities and orbital parameters, taking account of selection effects.

We present a cautionary study characterizing the influence of non-solar abundance ratios on Hδ derived ages in the integrated light of early-type galaxies. We measure Hδ using a variety of index measurements designed to assess contamination from CN molecular lines in and around the Hδ feature. We propose that neighboring CN lines have a strong effect on continuum levels and the Hδ feature itself, thereby leading to a difficulty in designing an accurate Hδ index definition in populations with C andor N non-solar abundance ratios with population synthesis models that do not account for such variations.