Massive black holes (MBHs) with a mass below ~ 107 M⊙ are likely to reside at the centre of dense stellar nuclei shaped by 2-body relaxation, close interactions with the MBH and direct collisions. In this contribution, we stress the role of mass segregation of stellar-mass black holes into the innermost tenths of a parsec and point to the importance of hydrodynamical collisions between stars. At the Galactic centre, collisions must affect giant stars and some of the S-stars.

Dwarf-galaxy sized dark matter halos may be detectable when a bright background source is gravitationally lensed on scales of milliarcseconds. Such effects can be caused by dark galaxies as well as luminous ones. Here we discuss conditions for detecting a luminous lensing object through direct imaging, via measurements of the point spread function (PSF) to subtract the quasar from the image, revealing the quasar host galaxy and any luminous lens. The technique applies to both types of millilensing effect, i.e. magnification and image splitting. We show that luminous dwarf-galaxy lenses should be detectable with this method up to redshifts z~0.2.

We review mid-infrared N-band spectra (8–13 μm) for a sample of 28 targets, obtained with the TIMMI2 camera at La Silla Observatory. The sample contains 5 FU Orionis stars, 6 Herbig Ae/Be objects, 7 T Tauri stars and 10 Vega-type main sequence objects. All targets show infrared excess, but for several the proof of circumstellar matter was lacking up to our observations. We model the N-band emission features with a mixture of silicates consisting of different grain sizes and composition, and determine the status of dust processing in these disks. While for some targets the emission spectrum resembles those of known pre-main sequence stars of evolved dust, other objects show strong isolated PAH bands but no silicate emission. For the first time we find evidence of PAH processing occurring in a T Tauri star. The Vega-type object HD 113766 exhibits highly-processed secondary generation dust, likely released by the collision of planetesimal-sized bodies. The findings of our dust analysis are set in context to previous dust studies of young stellar objects.

The potential advantages of the new generation of Extremely Large Telescopes are briefly summarized. When used in combination with advanced adaptive optics modules which can substantially remove the effect of atmospheric turbulence at infrared wavelengths, these telescopes will provide unique capabilities both in terms of photon collecting power (→2-4 magnitude advantage) and angular resolution (4-5 times higher than with current 8-10m telescopes). The instruments under study for the TMT and E-ELT projects are presented and compared. I discuss the impact of the ELTs on three major science topics: stellar populations in galaxies to the Virgo distance, chemical abundances of the brighter stars in nearby galaxies and high redshift SN and GRBs.

Supermassive black holes are a key element in our understanding of how galaxies form. Most of the progress in this very active field of research is based on just ~30 determination of black hole masses, accumulated over the past decade. We illustrate how integral-field spectroscopy, and in particular our OASIS modeling effort can help improve the current situation.

Stellar mass compact object binaries are promising sources of gravitational radiation for the current generation of ground-based detectors, VIRGO and LIGO. Accurate templates for gravitational waveforms are needed in order to extract an event from the VIRGO/LIGO data stream. In the case of relativistic, compact object binaries accurate orbital parameters are necessary in order to produce such templates. Binary systems are affected by their stellar environment and thus the parameters of the binary population of a dense star cluster will be different from those of the field population. We propose to investigate the parameters of relativistic binary populations in dense star clusters using direct N-body simulations with a Post-Newtonian treatment of general relativity for the close binaries.

We are conducting a large survey with the Urumqi 25 m radio telescope to study the distribution and physical properties of massive star forming regions in the Milky Way. We will accomplish this by observing the H110α hydrogen recombination line at 4.874 GHz and the H2CO absorption line at 4830 GHz. These lines are associated with compact HII regions and dense molecular clouds. As a test of the 6 cm spectral line receiving system, we observed the two spectral lines toward massive star forming regions. We plan to study the large scale distribution and physical properties of massive star forming regions in the Milky way.

Using the VLBA, we have observed H2O maser emission in the pre-planetary nebula, IRAS 19134+2131 (I1913), in which the H2O maser spectrum has two groups of emission features separated in radial velocity by ~100 km s−1. The morphology and 3-D kinematics indicate the existence of a fast collimated flow with a dynamical age of only ~40 years. Such a “water fountain” source is a signature of the recent operation of a stellar jet, that may be responsible for the final shape of the planetary nebula into which I1913 is expected to evolve. We have also estimated the distance to I1913 (~8 kpc) on the basis of an annual parallax and the kinematics of IRAS 19134+2131 in our Galaxy. I1913 may be a component in the “thick disk” or the Galactic “warp”, whose kinematics is different from that of the Galactic “thin” disk. These results are reported in Imai, Sahai & Morris (2007).

Division XII consists of Commissions that formerly were organized under the Executive Committee, that concern astronomers across a wide range of scientific sub-disciplines and provide interactions with scientists in a wider community, including governmental organizations, outside the IAU.

Galactic Giant Molecular Cloud (GMC) complexes are among the largest objects in the sky. In order to get the full picture of Galactic star formation a large field of view is important. The Allen Telescope Array (ATA) is the first of a new generation of large-N, small-D radio telescopes designed to provide high quality images on large angular scales. We present here the first wide field images of GMCs made with the ATA.

We study observed correlations between supermassive black hole (BHs) and the properties of their host galaxies, and show that the observations define a BH “fundamental plane” (BHFP), of the form or , analogous to the FP of elliptical galaxies. The BHFP is preferred over a simple relation between MBH and any of σ, M*, Mdyn, or Re alone at > 3 σ (99.9%) significance. The existence of this BHFP has important implications for the formation of supermassive BHs and the masses of the very largest black holes, and immediately resolves several apparent conflicts between the BH masses expected and measured for outliers in both the MBH − σ and MBH − M* relations.

We investigate the behaviour of dust in protoplanetary disks under the action of gas drag using our 3D, two-fluid (gas+dust) SPH code. We present the evolution of the dust spatial distribution in global simulations of planetless disks as well as of disks containing an already formed planet. The resulting dust structures vary strongly with particle size and planetary gaps are much sharper than in the gas phase, making them easier to detect with ALMA than anticipated. We also find that there is a range of masses where a planet can open a gap in the dust layer whereas it doesn't in the gas disk. Our dust distributions are fed to the radiative transfer code MCFOST to compute synthetic images, in order to derive constraints on the settling and growth of dust grains in observed disks.

We observed with VERA the massive star forming region G34.4+0.23, to obtain parallaxes and proper motions. Four infrared dark clouds were observed and water maser were found in two dark clouds, MM1 and MM4. In MM1, the distribution of maser spots shows a “V-shaped” structure and most features co-moving with this structure. Phase-referenced images have peaks and their motion is much larger than the expected parallax. Further analysis is needed to correctly interpret our measurement of parallax.

We explore the possibility that all close binaries, i.e. those with periods < 3 days, including contact binaries, are produced from initially wider binaries by the action of a triple companion through the medium of Kozai Cycles with Tidal Friction (KCTF).

The Local Supercluster is an ideal laboratory to study distribution of luminous and dark matter in the nearby Universe. The 1100 small groups have been selected using algorithm based on assumption that a total energy of physical pair of galaxies must be negative. The properties of the groups have been considered.

Commission 5 has been very active during the IAU XXVI General Assembly in Prague: the Commission, its Working Groups and its Task Force held business meetings. In addition, Commission 5 sponsored two Special Sessions: Special Session 3 on The Virtual Observatory in Action: New Science, New Technology, and Next Generation Facilities which was held for three days 17–22 August, and Special Session 6 on Astronomical Data Management, which was held on 22 August. Commission 5 also participated in the organisation of Joint Discussion 16 on Nomenclature, Precession and New Models in Fundamental Astronomy, which was held 22-23 August. The General Assembly and Commission 5 web sites provides links to detailed information about all these meetings.

While the broad-lined Type Ic supernovae (SN Ic-bl) associated with long-duration gamma-ray bursts (GRBs) have been studied, we do not fully understand the conditions that lead to each kind of explosion in a massive star. Here we show clues as to the production mechanism of GRBs by comparing the chemical abundances at the sites of 5 nearby (z < 0.25) broad-lined SN Ic that accompany nearby GRBs with those of 12 nearby (z < 0.14) broad-lined SN Ic that have no observed GRBs. We show that the oxygen abundances at the GRB sites are systematically lower than those found near ordinary broad-lined SN Ic. A unique feature of this analysis is that we present new spectra of the host galaxies and analyze the measurements of both samples in the same set of ways, using 3 independent metallicity diagnostics. We demonstrate that neither SN selection effects (SN found via targeted vs. non-targeted surveys) nor the choice of strong-line metallicity diagnostic can cause the observed trend. Though our sample size is small, the observations are consistent with the hypothesis that low metal abundance is the cause of some massive stars becoming SN-GRB. We derive a cut-off metallicity of 0.2−0.6 Z⊙, with the exact value depending on the adopted metallicity scale and solar abundance value.

At the 2003 Sydney IAU meeting, Marion Schmitz (Caltech, USA) took over the chair of the Commission 5 Working Group Designations, succeeding Helene Dickel. The Working Group Designations of IAU Commission 5 clarifies existing astronomical nomenclature and helps astronomers avoid potential problems when designating their sources. The most important function of WG Designations during the period 2003-2005 was overseeing the IAU REGISTRY FOR ACRONYMS (for newly discovered astronomical sources of radiation: see the website <http://cdsweb.u-strasbg.fr/cgi-bin/DicForm>) which is sponsored by the WG and operated by the Centre de Données de Strasbourg (CDS). The Clearing House, a subgroup of the WG, screens the submissions for accuracy and conformity to the IAU Recommendations for Nomenclature (<http://cdsweb.u-strasbg.fr/iau-spec.html>). From its beginning in 1997 through August 2006, there have been 132 submissions and 111 acceptances. Attempts to register asterisms, common star names, and suspected variable stars were rejected. The past three years saw 61 acronyms submitted with 50 of them being accepted. (GIRL - yes; WOMEN - no).

OH masers at 1720 MHz have proven to be excellent indicators of interactions between supernova remnants and molecular clouds. Recent calculations suggest that the 6049 MHz OH maser line is excited at higher column densities than for the 1720 MHz line. It is therefore a potentially valuable indicator of remnant-cloud interaction.

We present preliminary results of a survey using the Parkes Methanol Multibeam receiver for 6049 MHz and 6035/6030 MHz OH masers towards 36 supernova remnants and four fields in the Large and Small Magellanic Clouds. While no 6049 MHz masers have been found, three new sites of 6035 and 6030 MHz OH maser emission have been discovered in star-forming regions.

We have performed monitoring observations of the 3-mm flux density toward the Galactic center compact radio source Sgr A* with the ATCA since 2005 October. It has been found that during several observing epochs Sgr A* was quite active, showing significant intraday variation. Here we report the detection of an IDV in Sgr A* on 2006 August 13, which exhibits a 27% fractional variation in about 2 hrs.