The distribution of baryons beyond galaxies is descibed. The majority of the baryons, which represent 4% of the cosmic mass and energy budget, lie far from individual galaxies in the diffuse intergalactic medium (IGM). Many of these baryons are in a warm phase that can be probed by quasar absorption in the Lyman-α line of hydrogen. The mature field of quasar spectroscopy can diagnose the location, physical state, metallicity, and general geometry of this gas, which is called the “cosmic web.” The remainder of the gas is kept very hot by infall and shocks and is mostly in higher density regions such as filaments, groups and clusters. The hot gas is only detectable via X-rays and the absorption of highly ionized species of heavy elements. The baryons in low density regions of space are excellent tracers of underlying dark matter. The evolution of the cosmic web indicates where to look for the baryons in collapsed objects but the overall inefficiency of galaxy formation has conspired to keep most baryons dark.

This report of the business meeting at the 2006 IAU GA is based on notes provided by Edward Tedesco, past president, and on the minutes taken by Petrus Jenniskens, secretary of Commission 15 in the triennium 2003 to 2006, with additional notes from the current secretary of Commission 15, Daniel Boice. For political reasons the incoming President, Walter Huebner, was unable to attend the General Assembly.

An emerging conclusion of theoretical supernova research is that the breaking of spherical symmetry may be the key to the elusive mechanism of explosion. Such explorations require state-of-the-art multi-dimensional numerical tools and significant computational resources. Despite the thousands of man-years and thousands of CPU-years devoted to date to studying the supernova mystery, both require further evolution. There are many computationally-challenging instabilities in the core, before, during, and after the launch of the shock, and a variety of multi-dimensional mechanisms are now being actively explored. These include the neutrino heating mechanism, the MHD jet mechanism, and an acoustic mechanism. The latter is the most controversial, and, as with all the contenders, requires detailed testing and scrutiny. In this paper, we analyze recent attempts to do so, and suggests methods to improve them.

N-body simulations of open cluster evolution with primordial binaries are reviewed. In particular, recent results arising from models with initial N in the range of 20000–100000 bodies are compared to earlier idealized models with N ~ 2000. Efforts to model real clusters are discussed, including how limitations of the models such as simplified initial conditions will be addressed in the near future.

We present results on the oscillatory properties (periods, damping rates, and spatial distribution of perturbations) for resonantly damped oscillations in a system of two inhomogeneous coronal slabs and compare them to the properties found in single slab loop models. A system of two identical coronal loops is modelled, in Cartesian geometry, as being composed by two density enhancements. The linear magnetohydrodynamic (MHD) wave equations for oblique propagation of waves are solved and the damping due to resonant absorption is computed. Due to the interaction between the loops, the normal modes of oscillation present in a single slab split into symmetric and antisymmetric oscillations when a system of two identical slabs is considered. The frequencies of these solutions may differ from the single slab results when the distance between the loops is of the order of a few slab widths. Oblique propagation of waves weakens this interaction, since solutions become more confined to the edges of the slabs. The damping is strong for surface-like oscillations, while sausage body-like solutions are unaffected.

The birth of a young star is accompanied not only by accretion but by the expulsion of matter as well in the form of a collimated outflow. These outflows are seen at various wavelengths from X-rays to the radio band, but ultimately the driving mechanism appears to be a highly collimated supersonic jet that contains not only atomic but molecular components as well. These jets may also play a key role in the star formation process itself since they could be one of the primary mechanism for removing angular momentum from the accretion disk thereby allowing accretion to occur. Whereas much is known about their propagation on large-scales (i.e., hundreds of AU to several parsecs) from both observations and simulations, we must explore the “central engine” in order to understand how they are generated. While this is particularly challenging, high spatial resolution studies are beginning to reveal interesting data from which we can confront the various models. In this review, I will summarise what these studies suggest and note how they already favour certain models over others. I will also describe some of the results from spectro-astrometry and interferometry that are revealing details of outflows on milliarcsecond scales from the source.

The majority of extra-solar planets have been discovered by measuring the Doppler velocities of the host star. Like all exoplanet detection methods, the Doppler method is rife with observational biases. Before any robust comparison of mass, orbital period and eccentricity distributions can be made with theory, a detailed understanding of these selection effects is required, something which up to now is lacking. We present here a progress report on our analysis of the selection effects present in Anglo-Australian Planet Search data, including the methodology used and some preliminary results.

This paper reports on our observing campaign of faint satellites performed at the National Time Service Center and Sheshan station of SHAO from 1994 up to today. In the past few years due to benefit from using a large size CCD and the publication of the modern catalogues (UCAC2), a series of observations of faint satellites were obtained by us. Moreover the work of improving the orbit of Phoebe via numerical fit to the observations over a century is also presented.

We present the results of spectral energy distribution analysis for 162 of the 405 sources reported in the SIMBA survey of Hill et al. (2005). The fits reveal source specific parameters including: the luminosity, mass, temperature, H2 number density, the surface density and the luminosity-to-mass ratio. Each of these parameters are examined with respect to the four classes of source present in the sample. Obvious luminosity and temperature distinctions exist between the mm-only cores and those cores with methanol maser and/or radio continuum emission, with the former cooler and less luminous than the latter. The evidence suggests that the mm-only cores are a precursor to the methanol maser in the formation of massive stars. The mm-only cores comprise two distinct populations distinguished by temperature. Analysis and conclusions about the nature of the cool-mm and warm-mm cores comprising the mm-only population are drawn.

We present discovery of compact elliptical galaxies in the centres of clusters and briefly discuss their evolution.

We outline the steps needed in to calibrate the Monte Carlo code in order to perform large scale simulations of real globular clusters. We calibrate the results against N-body simulations for N = 2500, 10000 and for the old open cluster M67. The calibration is done by choosing appropriate free code parameters.

Methanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.

The meeting of the Physical Properties of the Minor Planets Working Group of IAU Commission 15 took place on 24 August, and was devoted to purely scientific matters, since other topics (organization of the Minor Planet WG, need of a new web page, election of the new chairman) had been already discussed during the business meeting of Commission 15, on 22 August. A brief summary of the talks given during the meeting is given in what follows.

I discuss observational clues concerning episodic mass-loss properties of massive stars in the time before the final supernova explosion. In particular, I will focus on the mounting evidence that LBVs and related stars are candidates for supernova progenitors, even though current paradigms place them at the end of core-H burning. Namely, conditions in the immediate circumstellar environment within a few 102 AU of Type IIn supernovae require very high progenitor mass-loss rates. Those rates are so high that the only known stars that come close are LBVs during rare giant eruptions. I will highlight evidence from observations of some recent extraordinary supernovae suggesting that explosive or episodic mass loss (a.k.a. LBV eruptions like the 19th century eruption of Eta Car) occur in the 5-10 years immediately preceding the SN. Finally, I will discuss some implications for stellar evolution from these SNe, the most important of which is the observational fact that the most massive stars can indeed make it to the ends of their lives with substantial H envelopes intact, even at Solar metallicity.

I present and discuss a unified scheme for jet launching that is based on stochastic dissipation of the accretion disk kinetic energy, mainly via shock waves. In this scheme, termed thermally-launched jet model, the kinetic energy of the accreted mass is transferred to internal energy, e.g., heat or magnetic energy. The internal energy accelerates a small fraction of the accreted mass to high speeds and form jets. For example, thermal energy forms a pressure gradient that accelerates the gas. A second acceleration stage is possible wherein the primary outflow stretches magnetic field lines. The field lines then reconnect and accelerate small amount of mass to very high speeds. This double-stage acceleration process might form highly relativistic jets from black holes and neutron stars. The model predicts that detail analysis of accreting brown dwarfs that launch jets will show the mass accretion rate to be ṀBD ≳ 10−9 − 10−8M⊙ yr−1, which is higher than present claims in the literature.

The accuracy of planetary satellites ephemerides is determined not only by the accuracy of dynamical model (internal accuracy) but also by the accuracy of the observations (external accuracy) used to fit the initial parameters of a model. This external accuracy extrapolated in the future is unknown most of the time and tends to degrade the global accuracy of ephemerides. Even if we can estimate the quality of the ephemerides by comparison with observations, we do not know how to determinate the evolution of the accuracy outside the period of observations. We will present a statistical method, resampling of observations, which allows a better estimation of the extrapolated accuracy in the future.

TRACE observations (23/11/1998 06:35:57-06:48:43UT) in the 171 Å bandpass of an active region are studied. Coronal loop oscillations are observed after a violent disruption of the equilibrium. The oscillation properties are studied to give seismological estimates of physical quantities, such as the density scale height. A loop segment is traced during the oscillation, and the resulting time series is analysed for periodicities. In the loop segment displacement, two periods are found: 435.6±4.5 s and 242.7±6.4 s, consistent with the periods of the fundamental and 2nd harmonic fast kink oscillation. The small uncertainties allow us to estimate the density scale height in the loop to be 109 Mm, which is about double the estimated hydrostatical value of 50 Mm. The eigenfunction is used to do spatial coronal seismology, but that method does not give any conclusive results.

We use numerical simulations to study how the spatial distribution and kinematics of globular cluster systems (GCS) are affected by galaxy mergers. Each progenitor galaxy is given a GCS modeled after the Galactic GCS. We then study how a major merger affects the spatial distribution and kinematics of the GCS. Here we present our methodology. Future work will investigate the effects of varying galaxy parameters, merger orbital parameters, and initial GCS number density profile and kinematics. We hope to be able to extract information about the merger history of a galaxy from observations of its GCS spatial distribution and kinematics.

To achieve maximum planet yield for a given radial velocity survey, the observing strategy must be carefully considered. In particular, the adopted cadence can greatly affect the sensitivity to exoplanetary parameters such as period and eccentricity. Here we describe simulations which aim to maximise detections based upon the target parameter space of the survey.

While the baryon fraction in galaxy groups and clusters may be expected to reflect the universal value, observations of cluster baryon fractions have generally fallen short of this expectation and indicated a possible correlation with cluster mass. We present a new determination of the total baryon budget in nearby galaxy groups and clusters that includes the contributions from stars in galaxies, intracluster stars, and the intracluster medium. We find that the baryon mass fraction within r500 is independent of system mass and lower than the WMAP value. We conclude however that the present shortfall provides no compelling evidence for additional missing baryons, since it may arise due to a theoretically predicted deficit of baryons within r500 and systematic uncertainties associated with the mass determinations. With the addition of the ICL to the stellar mass in galaxies, the increase in X-ray gas mass fraction with increasing total mass is entirely accounted for by a decrease in the total stellar mass fraction, supporting the argument that the behavior of both the stellar and X-ray gas components is dominated by a decrease in star formation efficiency in more massive environments. Within just the stellar component, the fraction of the total stellar luminosity in the central, giant brightest cluster galaxy (BCG) and ICL (hereafter the BCG+ICL component) decreases as velocity dispersion (σ) increases, suggesting that ICL may grow less efficiently in higher mass environments. The identification of low mass groups with large BCG+ICL components also demonstrates that the massive cluster environment is not required to form intracluster stars. These proceedings are a condensed version of the work presented in Gonzalez, Zaritsky & Zabludoff (2007), and we refer the reader to that paper for a more complete discussion.