We study nearby X-ray-emitting dusty elliptical galaxies in mid- and far-infrared by using the Spitzer Space Telescope and AKARI, the Japanese infrared astronomical satellite.

The spacecraft Hayabusa, which was launched in 2003, arrived at its destination, asteroid (25143) Itokawa in September 2005. The appearance of Itokawa, a small S-type near Earth asteroids, was totally unexpected. The surface is covered with a lot of boulders and there are only a few craters on it. It looks like a contact binary asteroid. The surface composition is quite similar to LL-chondrite. The estimated density is 1.9 ± 0.13 (g/cm3), so the macro-porosity is about 40%. This means that Itokawa is a rubble pile object. In Itokawa, we may see such things that are very close to building blocks of asteroids. In this paper, we review the mission and the first scientific results.

Results of the Venus Express mission to Venus are summarized.

The IRAIT (International Robotic Antarctic Infrared Telescope) project (Tosti et al. 2006) is based on a 80 cm aperture telescope to observe in the infrared range. It is due to start operations in spring 2008, several months after installation in Dome C (Antarctica). We describe the contributions made to such project by the Institute for Space Studies of Catalonia (IEEC) and the University of Granada, whose participation has been mainly focused in developing the moving optical system for the secondary (M2) and tertiary (M3) mirrors of the telescope. Moving parts of the optical system provide focusing and chopping capabilities, implemented in M2, and a rotation mechanism, implemented in M3, allow observation in either Nasmyth foci. The work package includes the design and construction of both mirrors, the mechanical supports, the electronics and the control software, all prepared to work at the low temperatures at Antarctica. A Spanish company, NTE, was contracted to carry out the design and manufacture. Tests at low temperature and integration in the telescope were finished during summer 2006, before sending the telescope to Antarctica, scheduled by the end of the same year.

We investigate the influence of metallicity and wind mass loss on the radii of luminous Wolf-Rayet stars.

Stellar multiplicity is a fundamental astrophysical property. In addition to being the only physical basis for accurate mass determination, this parameter is believed to influence important aspects such as planet formation and stability. Contrary to earlier expectations, recent studies have shown that even against selection biases, as many as 23% of the planetary systems reside in multiple star systems (Raghavan et al. 2006)). Leveraging recent efforts in identifying stellar and substellar companions to solar-type stars, and augmenting them with targeted observations, we are conducting a comprehensive survey, aimed at providing a modern update to the seminal work of Duquennoy & Mayor (1991). The details of our sample, survey methods, and some preliminary results are presented here.

We present a multiwavelength analysis of a compact group infalling at high speed (~1700 km s−1) into the dynamically young cluster Abell 1367. Peculiar morphologies and unusually high Halpha emission are associated with two giant galaxies and at least ten dwarfs/extragalactic HII regions, making this group the region with the highest density of star formation activity ever observed in the local clusters. Moreover Halpha imaging observations reveal extraordinary complex trails of ionized gas behind the galaxies, with projected lengths exceeding 100 kpc. These unique cometary trails mark the gaseous trajectory of galaxies, witnessing their dive into the hot cluster intergalactic medium. Under the combined action of tidal forces among group members and the ram-pressure by the cluster ambient medium, the group galaxies were fragmented and the ionized gas was blown out. The properties of this group suggest that environmental effects within infalling groups may have represented a preprocessing step of the galaxy evolution during the high redshift cluster assembly phase.

Galaxy bimodality is caused by the bulge-disc nature of galaxies as opposed to two distinct galaxy classes. This is evident in the colour-structure plane which clearly shows that elliptical galaxies (bulge-only) lie in the red compact peak and late-type spiral galaxies (disc-dominated) lie in the blue diffuse peak. Early-type spirals (bulge plus disc systems) sprawl across both peaks. However after bulge-disc decomposition the bulges of early-type spirals lie exclusively in the red compact peak and their discs in the blue diffuse peak (exceptions exist but are rare, e.g., dust reddened edge-on discs and blue pseudo-bulges). Movement between these two peaks is not trivial because whilst switching off star-formation can transform colours from blue to red, modifying the orbits of ~1 billion stars from a planar diffuse structure to a triaxial compact structure is problematic (essentially requiring an equal mass merger). We propose that the most plausible explanation for the dual structure of galaxies is that galaxy formation proceeds in two stages. First an initial collapse phase (forming a centrally concentrated core and black hole), followed by splashback, infall and accretion (forming a planar rotating disc). Dwarf systems coule perhaps follow the same scenario but the lack of low luminosity bulge-disc systems would imply that the two components must rapidly blend to form a single flattened spheroidal system.

Compact groups are highly isolated, dense galaxy systems, and therefore tidal interactions are expected to be continuous and dynamically important. For this reason they represent unique laboratories for studying interactions in extreme environments and tidally induced star formation as well as morphological and dynamical evolution of galaxies in general. This study is part of a broader investigation of the evolutionary status of HCGs. In order to explain the HI deficiency found in compact groups of galaxies we have proposed a broad evolutionary scenario in which the amount of HI decreases with the secular evolutionary state of a group. The fate of this gas is however not clear. In order to investigate the physical mechanisms responsible for these changes in the gas content of galaxies we have started a study to look for an intragroup medium (IGM). We have considered this IGM to be neutral (see e.g. reports of HI clouds within Virgo cluster (Oosterloo & Van Gorkom 2005), or hot gas (a higher X-ray detection rate of HI deficient groups is found relative to groups with a normal HI content, Verdes-Montenegro et al. 2001). Enhanced star formation activity might also be contributing to exhausting the gas supply. We have observed 25 HCGs with diverse HI content and distribution with the Green Bank radiotelescope, and performed VLA-HI as well as X-ray (XMM or Chandra) observations of the most HI deficient groups HCG 7, 15, 30, 37, 40, 44 and 97. We have also analysed FIR data from Verdes-Montenegro et al. (1998).

Our results are: (a) HI deficient groups show a larger amount of diffuse neutral and X-ray gas when compared to non-deficient ones, consistent with our evolutionary picture; (b) Most groups are still deficient after including diffuse gas. (c) A hot IGM is not detected in most of these systems, but the detection rate is higher for the high velocity dispersion groups, and in these cases ram pressure stripping could potentially cause the observed HI-deficiency. (d) In several of these groups we detect intragroup radio continuum emission, which is surprising since similar features were seen previously only in massive clusters (known as “relic” sources). (e) Star formation activity traced by FIR luminosity is not enhanced, contrary to the general expectation of tidally interacting systems.

Hence neither the presence of a hot or cold IGM nor star formation activity seem to be able to uniquely explain the HI deficiency found in compact groups of galaxies. We plan to explore the possibility that earlier starbursts could have contributed to the present HI deficiency.

We studied the orbital evolution of objects with initial orbits close to those of Jupiter-family comets (JFCs), Halley-type comets (HTCs), and long-period comets, and the probabilities of their collisions with the planets. In our runs the probability of a collision of one object with the Earth could be greater than the sum of probabilities for thousands of other objects. Even without the contribution of such a few objects, the probability of a collision of a former JFC with the Earth during the dynamical lifetime of the comet was greater than 4×10−6. This probability is enough for delivery of all the water to Earth's oceans during the formation of the giant planets. The ratios of probabilities of collisions of JFCs and HTCs with Venus and Mars to the mass of the planet usually were not smaller than that with Earth. Among 30,000 considered objects with initial orbits close to those of JFCs, a few objects got Earth-crossing orbits with semimajor axes a<2 AU and aphelion distances Q<4.2 AU, or even got inner-Earth (Q<0.983 AU), Aten, or typical asteroidal orbits, and moved in such orbits for more than 1 Myr (up to tens or even hundreds of Myr). From a dynamical point of view, the fraction of extinct comets among near-Earth objects can exceed several tens of percent, but, probably, many extinct comets disintegrated into mini-comets and dust during a smaller part of their dynamical lifetimes.

We study giant radio sources at long wavelengths.

Bright knots along the arms of grand-design spiral galaxies are frequently seen on near-infrared K-band images. To investigate their nature, low resolution K-band spectra of a string of knots in the southern arm of the grand design, spiral galaxy NGC 2997 were obtained with ISAAC/VLT. Most of the knots show strong Brγ emission while some have H2 and HeI emission. A few knots show indications of CO absorption. Their spectra and absolute K magnitudes exceeding -12 mag suggest them to be very compact, young stellar clusters with masses up to 5 × 104 M. The knots' azimuthal distance from the K-band spiral correlates well with their Brγ strength, indicating that they are located inside the co-rotation of the density wave, which triggered them through a large-scale, star-forming front. These relative azimuthal distances suggest an age spread of more than 1.6 Myr, which is incompatible with standard models for an instantaneous star burst. This indicates a more complex star-formation history, such as several bursts or continuous formation.

We report on the discovery of a supermassive binary black-hole (SBBH) system in the radio galaxy 0402+379, with a projected separation between the two black holes of just 7.3 pc. This is the most compact SBBH pair yet imaged by more than two orders of magnitude. These results are based upon multi-frequency imaging using the Very Long Baseline Array (VLBA) which reveal two compact, variable, flat-spectrum, active nuclei within the elliptical host galaxy of 0402+379. Multi-epoch observations from the VLBA also provide constraints on the total mass and dynamics of the system. The two nuclei appear stationary while the jets emanating from the weaker of the two nuclei appear to move out and terminate in bright hot spots. The discovery of this system has implications for the number of compact binary black holes that might be sources of gravitational radiation. The VLBI Imaging and Polarimetry Survey (VIPS) currently underway should discover several more SBBHs.

We present optical R band photometry of nine X-ray selected BL Lac objects: 1ES 0229+200, 1ES 0323+022, 1ES 502+675, 1ES 0647+250, 1ES 0806+524, 1ES0927+500, 1ES 1028+511, 1ES 1959+650, 1ES2344+514.

Variability on long time scales within one magnitude in R band was found for all of the observed objects, except 1ES 0229+200 and 1ES0927+500. Largest variation was detected for 1ES 0502+675 and equals to 1.07 mag. Only few objects show statistically significant variation on intra-day scale.

We performed numerical simulation including UV radiation transfer, and investigated effects of radiation driven implosion on star formation processes. We also observed two bright-rimmed clouds with C12O(J=1-0) and C13O(J=1-0) in order to compare density distributions between numerical results and observational results. Density profiles of bright-rimmed clouds are consistent with those of numerical simulations. These facts insist that star formations in bright-rimmed clouds are triggered by radiation driven implosion.

After a brief description of the ESA Science Programme, the long-term plan for Astrophysics is described, as well as possible strategies for its implementation.

External shock triggering and internal turbulence play major role for the condensation of the ISM and star formation. Some evidences of shock triggering by non-isotropic compression are seen in the cloud morphologies and associated active cluster formation such as the ρ Oph and Cha I clouds. Surveys for C18O dense cores have shown that internal turbulence dominates the core dynamics and regulates star formation activity (Tachihara et al. 2002).

High-resolution adaptive optics observations of the inner 0.5 pc of the Milky Way with multiple intermediate band filters are presented. From the images, stellar number counts and a detailed map of the interstellar extinction were extracted. The extinction map is consistent with a putative southwest-northeast aligned outflow from the central arcseconds.

An azimuthally averaged, crowding and extinction corrected stellar density profile presents clear evidence for the existence of a stellar cusp around Sgr A*. Several density peaks are found in the cluster that may indicate clumping of stars, possibly related to the last epoch of star formation in the Galactic Center. An analysis of stars in the brightness range 14.25 < magK < 15.75 shows possible signs of mass segregation.

We discuss the issue of retrieving diurnal and semi-diurnal signals in Earth rotation from VLBI observations.

We study a possibility of tidal disruptions of stars orbiting a supermassive black hole due to eccentricity oscillations driven by Kozai's mechanism. We apply the model to conditions relevant for the Galactic Centre where we consider two different sources of the perturbation to the central potential, which trigger the resonance mechanism. Firstly, it is a disc of young massive stars orbiting Sgr A* at r ≳ 0.08 pc, and, secondly, a molecular circumnuclear disc. Each of the two possibilities appears to be capable of exciting eccentricities to values sufficient for the tidal disruption of ∼100 stars from the nuclear stellar cluster on a time-scale of 0.1–10 Myrs. Tidally disrupted stars may cause periods of increased accretion activity of Sgr A*.