Before reviewing the radio properties of active spiral galaxies it is appropriate, as well as instructive, to think about a working definition of an active galaxy. This may seem a trivial point when we consider classes of objects like Seyfert galaxies or radio galaxies but this is much less so when we inspect the nearby systems. In a sample of nearby galaxies one is likely to encounter much more milder forms of activity than that known from studies of more distant galaxies. This is, of course, due to the fact that the latter have been selectively taken from a much larger reservoir of objects. (Although this may seem a disadvantage from an observational point of view, there are some clear advantages as well. Firstly, we can obtain a much better linear resolution once we have been able to isolate the active nearby galaxies and, secondly, we eventually may hope to learn more about the physical situation that existed prior to the onset of the active period and how the surrounding medium reacts to the activity.)

The solar granulation has been simulated by numerical solution of the multidimensional, time-dependent, nonlinear Navier-Stokes equations applied to the solar atmosphere. Granules may be explained as buoyantly rising bubbles created at the level where T = 8000 K, and which have collapsed into vortex rings. The calculation is in quantitative agreement with observations and has a number of implications for solar physics and convection theory.

I briefly present the most relevant observational facts supporting the idea of one or more star formation episodes in globular clusters.

Recent observations demonstrate that dwarf galaxies in clusters, despite their faintness, may be a critical galaxy type for understanding the physical processes behind galaxy formation. Dwarfs are the most common type of galaxy and are particularly abundant in rich galaxy clusters. The dominate model for explaining the formation of these systems thorough Cold Dark Matter models is that the bulk of their stellar mass formed early, and within their present environments. Recent results however suggest that some dwarfs appear in clusters after the bulk of its members form, a scenario not predicted in standard hierarchical structure formation models. Many of these systems appear to be younger and more metal rich than dwarfs in lower density areas, suggesting they are possibly created by a tidal process induced by the cluster. Several general galaxy cluster observations, including steep luminosity functions and the origin of intracluster light, are natural outcomes of these processes.

Arabic star names are well known in two areas: in the Orient itself, i.e. in the Arabic-Islamic civilization, and in the West where many of them were adopted since mediaeval times and continued to be used until today.

The complex known in modern Western astronomy as “Arabic star names” is the result of a historical development of almost exactly one thousand years. In mediaeval times, those names were introduced into Western use by Latin translations of Arabic astronomical and astrological works. Afterwards, since Humanist and Renaissance times, and until this present century, Western astronomers used to pick up more “Arabic” names from philological studies of orientalists who tried to describe and explain the stellar nomenclature of the Arabs and other Oriental peoples. As outstanding examples, I mention the studies of Joseph Scaliger and his follower Hugo Grotius (both printed in 1600) whose nomenclature was borrowed by Johannes Bayer into his star atlas Uranometria of 1603; Thomas Hyde’s commentary to his edition of Ulugh Bēg’s star catalogue (Oxford, 1665) from which Giuseppe Piazzi borrowed a great number of names into the second edition of his Palermo Catalogue, 1814; German studies by F.W.V. Lach (1796) and Ludwig Ideler (1809) which were used by continental astronomers such as J.E.Bode and many others; and still the book on star names by R.H. Allen (1899) from which several new names appear in astronomical books and atlases of our times.

Introductory remarks for IAU Symposium No. 84 are made. These include a brief history of previous symposia dealing with galactic structure, basic research problems in this area, and parallels regarding our galaxy which can be drawn from extragalactic research.

We present the first detailed three-dimensional hydrodynamic implicit large eddy simulations of turbulent convection for carbon burning. The simulations start with an initial radial profile mapped from a carbon burning shell within a 15 M⊙ stellar evolution model. We considered 4 resolutions from 1283 to 10243 zones. These simulations confirm that convective boundary mixing (CBM) occurs via turbulent entrainment as in the case of oxygen burning. The expansion of the boundary into the surrounding stable region and the entrainment rate are smaller at the bottom boundary because it is stiffer than the upper boundary. The results of this and similar studies call for improved CBM prescriptions in 1D stellar evolution models.

Hot luminous stars show a variety of phenomena in their photospheres and in their winds which still lack clear physical explanations at this time. Among these phenomena are non-thermal line broadening, line profile variability (LPVs), discrete absorption components (DACs), wind clumping and stochastically excited pulsations. Cantiello et al. (2009) argued that a convection zone close to the surface of hot, massive stars, could be responsible for some of these phenomena. This convective zone is caused by a peak in the opacity due to iron recombination and for this reason is referred to as the “iron convection zone” (FeCZ). 3D MHD simulations are used to explore the possible effects of such subsurface convection on the surface properties of hot, massive stars. We argue that turbulence and localized magnetic spots at the surface are the likely consequence of subsurface convection in early type stars.

Evolution in the merger rate as a function of redshift is in principle the key observable testing hierarchical models for the formation and evolution of galaxies. However, in practice, direct measurement of this quantity has proven difficult. In this opening review I outline the current best estimates for the merger rate as a function of cosmic epoch, focusing mostly upon recent advances made possible by deep ground-based redshift surveys and morphological studies undertaken with HST. I argue that a marriage of these techniques, in an attempt to determine the space density of mergers amongst the abundant morphologically peculiar population at high redshifts, is probably the most promising currently-available avenue for determining the prevalence of mergers at high redshifts. However, resolved kinematical studies, which seem set to become available in the next few years, are probably the best hope for a definitive determination of the space density of mergers at high redshifts.

In this work, we study the impactor flux on Pluto and Charon due to the collisional evolution of Plutinos.To do this, we develop a statistical code that includes catastrophic collisions and cratering events, and takes into account the stability and instability zones of the 3:2 mean motion resonance with Neptune. Our results suggest that if 1 Pluto-sized object is in this resonance, the flux of D = 2 km Plutinos on Pluto is ~4–24 percent of the flux of D = 2 km Kuiper Belt projectiles on Pluto. However, with 5 Pluto-sized objects in the resonance, the contribution of the Plutino population to the impactor flux on Pluto may be comparable to that of the Kuiper Belt. As for Charon, if 1 Pluto-sized object is in the 3:2 resonance, the flux of D = 2 km Plutinos is ~10–63 percent of the flux of D = 2 km impactors coming from the Kuiper Belt. However, with 5 Pluto-sized objects, the Plutino population may be a primary source of the impactor flux on Charon. We conclude that it is necessary to specify the Plutino size distribution and the number of Pluto-sized objects in the 3:2 Neptune resonance in order to determine if the Plutino population is a primary source of impactors on the Pluto-Charon system.

The recent discovery of a gravitational wave from the merging of two black holes of about 30 solar masses each challenges our incomplete understanding of massive stars and their evolution. Critical ingredients comprise mass-loss, rotation, magnetic fields, internal mixing, and mass transfer in close binary systems. The imperfect knowledge of these factors implies large uncertainties for models of stellar populations and their feedback. In this contribution we summarize our empirical studies of Wolf-Rayet populations at different metallicities by means of modern non-LTE stellar atmosphere models, and confront these results with the predictions of stellar evolution models. At the metallicity of our Galaxy, stellar winds are probably too strong to leave remnant masses as high as ~30 M⊙, but given the still poor agreement between evolutionary tracks and observation even this conclusion is debatable. At the low metallicity of the Small Magellanic Cloud, all WN stars which are (at least now) single are consistent with evolving quasi-homogeneously. O and B-type stars, in contrast, seem to comply with standard evolutionary models without strong internal mixing. Close binaries which avoided early merging could evolve quasi-homogeneously and lead to close compact remnants of relatively high masses that merge within a Hubble time.

A summary is given of the presentations delivered at IAU Symposium 231.

Supersoft X-ray sources are a new class of luminous X-ray binaries discovered with the X-ray telescopes of the Einstein and ROSAT satellites and extensively studied in the optical with ground based telescopes, in the UV with IUE and HST and in X-rays with ROSAT, Beppo-SAX and ASCA (cf. Kahabka & van den Heuvel 1997, van Teeseling 1997). The luminosities derived for a first sample of supersoft sources studied with moderate resolution X-ray spectroscopy (using Beppo-SAX LECS and ASCA SIS detectors, Parmar et al. 1997, Ebisawa et al. 1997) have been predicted to follow Iben’s stability line (Iben 1982), i.e. the location in the Hertzsprung-Russell diagram which separates the plateau phase from the cooling phase. This is not unreasonable as any system experiencing steady-state accretion, i.e. accretion at a rate equalling about the nuclear burning rate will be found close to the stability line. If the accretion rate exceeds this limit then the white dwarf gets bloated and disappears in X-rays. If the accretion rate falls below this limit the white dwarf envelope cools, the luminosity as well as the temperature ceases and the source enters unstable recurrent nuclear burning. From the population synthesis calculations of Yungelson (1996) follows that there exit for the Milky Way a few sources at any epoch which are more massive than 1.2 MQ. They are expected to be extremely X-ray bright and may be standard candles (cf. Table 1 and Figure 1 for the brightest known supersoft sources per galaxy Milky Way to NGC 55). Their spectral distribution is expected to be similar to that of the extremely hot galactic source RXJ0925.7-4758 (it peaks at 1 keV and the flux is distributed from 0.5 to 2 keV, see Figure 2 for the ASCA spectrum of RX J0925.7-4758 (and CAL 87) as derived by Ebisawa et al. 1997).

Global history of star or cluster formation in the Large Magellanic Cloud (LMC) has been the center of interest in several studies as it is thought to be influenced by tidal interaction with the Small Magellanic Cloud and even the Milky Way. This study focus on the formation history of the LMC in relation with the context of binary star clusters population, the apparent binary fraction (e.g., percentage of cluster pairs) in different epoch were calculated and analyzed. From the established distributions, it can be deduced that the binary clusters tend to be young (∽ 100 Myr) while their locations coincide with the locations of star forming complexes. There is an indication that the binary fraction increases as the rise of star formation rate in the last millions years. In the LMC, the increase of binary fraction at age ∽ 100 Myr can be associated to the last episode of close encounter with the Small Magellanic Cloud at ∽ 150 Myr ago. This observational evidence supports the theory of binary cluster formation through the fission of molecular cloud where the encounter between galaxies enhanced the clouds velocity dispersion which in turn increased the probability of cloud-cloud collisions that produce binary clusters.

This session opened with a crucial explanation by Michel Cotte of how astronomers first need to understand how to apply UNESCO World Heritage Criteria if they want to motivate their government(s) to make the case to UNESCO for World Heritage recognition. UNESCO World Heritage cannot be obtained just to protect dark skies.

Much more detail of this and the other presentations in this session, along with many images, can be found at the session website: http://www.noao.edu/education/IAUGA2015FM21.

The next speaker, John Hearnshaw, described the Aoraki Mackenzie International Dark Sky Reserve and the work it carries out . This was followed by a wide-ranging summary (by Dan Duriscoe and Nate Ament) of the U.S. National Park Service (NPS) Night Skies Program. The abstract of Cipriano's Marin's paper, “Developing Starlight connections with UNESCO sites through the Biosphere Smart" was shown in his absence. The final presentation (by Arkadiusz Berlicki, S. Kolomanksi and T. Mrozek) discussed the bi-national Izera Dark Sky Park.

Many high-mass X-ray binaries (HMXBs) are runaways. Stellar wind and radiation of donor stars in HMXBs along with outflows and jets from accretors interact with the local interstellar medium and produce curious circumstellar structures. Several such structures are presented and discussed in this contribution.

The richness of tidal features seen in interacting galaxies allows for the determination of their characteristic parameters, provided one can deal with the extended parameter space. Genetic algorithm based methods – like our code minga – have proven to be such a tool. Here I discuss the implementation of dark matter halo descriptions in the restricted N-body simulations of minga. I show that the final morphology of a galaxy encounter strongly depends on the halo properties. Thus, modeling tidal features of interacting galaxies might allow also for conclusions on the galactic dark matter content.

The Space Infrared Telescope Facility (SIRTF) is a one-meter class observatory for infrared astronomy that will be launched into high earth orbit by NASA in the late 1990’s. SIRTF’s three focal plane instruments will permit imaging and spectroscopy over most of the infrared spectrum with sensitivities of 100 to 10,000 times their predecessors. This paper briefly reviews SIRTF’s capabilities, science objectives, and current status.