We examine the effect of rotation on turbulent compressible penetrating convection, motivated by the dynamics of the solar interior. We find that rotation can influence large-scale coherent structures in the turbulent flow whilst leaving the small-scales isotropic. The dynamics in this case are very different from more laminar situations where all scales are rotationally-influenced. This may hint as to why full models of the global solar differential rotation are difficult.

The Semantic Web and ontologies are emerging technologies that enable advanced knowledge management and sharing. Their application to Astronomy can offer new ways of sharing information between astronomers, but also between machines or software components and allow inference engines to perform reasoning on an astronomical knowledge base. The first examples of astronomy-related ontologies are being developed in the european VOTech project.

We model the stochastic attenuation by HI absorbers in the intergalactic medium (IGM), such as Lyα Forest clouds, and absorbers associated with galaxies, such as Lyman Limit systems (LLS) and Damped Lyman Alpha absorbers (DLAs), and compute an ensemble of 4 · 103 attenuated Spectral Energy Distributions (SEDs) in the Johnson system for the spectrum of a galaxy with a constant star formation rate (CSFR). Using these, we asses the impact of the stochastic attenuation on the estimates of photometric redshifts for this type of galaxy by comparison with model SEDs that include only a mean attenuation.

Coordinate-independent definition of the characteristic, so-called “humpy” frequency related to the positive gradient of the orbital velocity in locally non-rotating frames around nearly extreme Kerr black holes is given and compared with the epicyclic and orbital frequencies for both Keplerian thin discs and limiting marginally stable thick discs.

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).

Following the report of the ‘task force’, the UK Government decided to accept some of it's recommendations. In particular, it accepted two that recommended the setting up of a British National Centre for Near Earth Objects. The final outcome was the setting up of a Near Earth Object Information Centre to inform the general public of the dangers or otherwise from impact on the Earth of Near Earth Objects. The Centre has now been running for several years and in this publication we examine the current workings of the Centre and discuss some of its successes and failures.

We present results on the properties and evolution of moderately ionized gas in the Universe based on intervening CIV absorption-line systems. We have compiled a database of CIV systems from the SDSS, and we find evidence for evolution in the incidence of CIV absorbers.

I present a brief review of some of the mid-infrared properties of interacting galaxies as these were revealed using observations from the Infrared Space Observatory and Spitzer Space Telescope over the last decade. The variation of the infrared spectral energy distribution in interacting galaxies can be used as an extinction free tracer not only of the location of the star formation activity but also of the physical mechanism dominating their energy production.‡.

The main goal of this work is to have a better understanding of the problems and characteristics of photometric surveys with small-sized affordable equipment, like the one available at the Astrophysics Division/INPE, in São José dos Campos, Brazil. The use of low-cost instruments is appealing in the context of the detection of Extrasolar Planets (ESP), in the sense that many observers are available for survey and follow-up programmes. It could also make possible the inclusion of many developing countries in the search for planetary transits. We describe the data collection and analysis procedure for differential photometry of the transit of HD 209458 b, using a small telescope and a commercial CCD camera. According to the HST observations of Brown et al. (2001), the transit produces a box-shaped light curve with 2% depth and 184-min duration. The orbital period is ∼ 3.5 days. The equipment consists of a f/10, 11” Schmidt-Cassegrain Celestron telescope equipped with a SBIG ST7E CCD camera. Since the seeing at the campus is quite poor, we used a focal reducer to produce an effective focal ratio of about f/5, still keeping a good sampling of the PSF but with a larger field of view. The larger field of view allows the simultaneous observation of a relatively bright nearby star, suitable for differential photometry. We discuss the IRAF reduction procedures for the large number of images collected and present the results obtained in the transit of September 8, 2004

I will discuss the search for galaxies and QSOs at the highest redshifts, out to the Epoch of Reionization. Observations in the submillimeter play a fundamental role in such searches, in particular once ALMA will become operational. I will focus on the properties of the molecular gas (the phase of the ISM out of which stars form) in the earliest systems as derived through observations in the millimetre and radio regime. These observations allow us to measure the reservoir of molecular gas and to constrain the physical properties and excitation of the gas. Resolved imaging of the host galaxies also allows us to derive first dynamical masses for these objects. Such mass determinations are critical to determine whether there is a possible evolution of the famous MBH–σbulge relation with redshift or not. Recent measurements in the QSO redshift record holder J1148+5251 (z= 6.42) provide evidence that the black hole in this system assembled before the stellar bulge.

The Observatorio Astronómico Los Molinos (OALM) is the only professional observatory in Uruguay. Its research activity is dedicated to the study of Small Bodies of the Solar System, i.e. comets and asteroids. It is one of the few observatories in the southern hemisphere dedicated to this topic. The observational programmes that we are conducting at present are described, putting especial emphasis in the results obtained last year.

We investigate the morphologies and velocity fields of spiral galaxies in distant clusters (z ~ 0.5) focussing on signatures from interactions. Structural parameters and peculiarities are determined with HST/ACS images. To derive the internal kinematics and rotation curves we have performed 3D–spectroscopy allowing the construction of the full velocity field for each galaxy. Combining both approaches, transformation mechanisms are revealed that affect not only the stellar populations but also the mass distribution. The observations are supported by N-body/SPH simulations of different interaction processes.

The star-formation histories, masses and structural properties of galaxies are strongly dependent on their environment: massive, passively-evolving spheroids dominate cluster cores, while in field regions, galaxies are typically low-mass, star-forming and disk-dominated (e.g Blanton et al. 2005). Equally the global properties of galaxies have been found to be bimodally distributed around a stellar mass of ~3 × 1010 M⊙ (~M*+1) (e.g. Kauffmann et al. 2003). Large-scale spectroscopic surveys have shown that the evolution of massive galaxies is primarily driven by their merger history, rather than through direct interection with the cluster environment, as demonstrated by the finding of massive passively-evolving galaxies in all environments, mild observed environmental trends for their mean stellar ages, and the gradual SF-density relation in which star-formation is still seen to be suppressed in galaxies 3–4 virial radii from the nearest cluster. In contrast, in the dwarf regime (>M*+2) dramatic changes are seen in both the luminosity function and red galaxy fraction between those galaxies in the cores of clusters and those at the virial radius (Mercurio et al. 2006, Haines et al. 2006a).

We have examined the origins of the bimodality observed in the global properties of galaxies by comparing the environmental dependencies of star-formation for giant and dwarf galaxy populations. Using SDSS DR4 spectroscopic data to create a volume-limited sample complete to M*+3, we find that the environmental dependences of giant and dwarf galaxies are quite different, implying fundamental differences in their evolution (Haines et al. 2006b). Whereas the star-formation histories of giant galaxies are determined primarily by their merger history, this is not the case for dwarf galaxies. In particular, we find that old or passive dwarf galaxies are ONLY found as satellites within massive halos (clusters, groups or giant galaxies), with none in the lowest density regions. This implies that star-formation in dwarf galaxies must be much more resilient to the effects of mergers, and that the evolution of dwarf galaxies is primarily driven by the mass of their host halo, through effects such as suffocation, ram-pressure stripping or galaxy harassment.

A CCD UBVRI survey of northern open clusters is being undertaken at San Pedro Mártir, México, and performed using always the same instrumental setup (telescope, CCD, filters), reduction methods, and system of standards of Landolt (1992). To date more than 300 clusters (mostly unstudied previously) have been observed, and about half the data reduced using aperture-photometry and PSF techniques. Our analysis procedures are being refined by studying in detail a small subset of these clusters. For example, the heavily reddened clusters Be80 and Be95 are being examined in the color-color diagrams: (B-V, U-B) and (B-V, R-I) to better understand the problems of curvature and variable reddening. For clusters for which our U data reaches the F-type stars, such as NGC2192 and NGC7296, techniques are being examined for estimating both the reddening E(B-V) and metallicity [Fe/H] via the use of the (U-B) excess. If the clusters also have “red clump” stars, such as NGC1798 and Do02, these procedures can be iterated between the clump and main sequence stars to establish even better the values of E(B-V) and [Fe/H]. Finally, color-magnitude diagrams, such as (B-V, V) and (V-I, V), are being employed together with the SchmidtKaler (1982) colors and Padova isochrones of Girardi et al. (2000) to obtain distances and ages for these clusters. A java-based computer program is being developed to help in the visualization and analysis of these photometric data. This system is capable of displaying each cluster simultaneously in different color-color and color-magnitude diagrams and has an interactive way to identify a star, or group of stars, in one diagram and to see were it falls in the other diagrams, facilitating the elimination of field stars and the apperception of cluster features. This program is capable of displaying up to 16 different diagrams for one cluster and processing up to 20 clusters at the same time. Our aims are the following: (1) a common UBVRI photometric scale for open clusters, (2) an atlas of color-color and color-magnitude diagrams for open clusters, (3) a homogeneous set of cluster reddenings, distances, and ages, (4) an increased number of old and distant open clusters, and (5) a selection of interesting clusters for further study.

One of the key predictions of hierarchical galaxy formation models is that a significant fraction of elliptical galaxies form in late merging events. One of the most important diagnostics of such an assembly is the existence of blue spheroidal galaxies, which have spheroid-dominated morphologies and blue colors indicating recent star formation, as an intermediate step in the evolution of elliptical galaxies.

Brown dwarf atmospheres are largely convective. These convective gas flows collide and feed back a whole spectrum of turbulent fluctuations into the atmospheric fluid field. Resulting non-static density and temperature fields influence the local chemistry concerning gas phase and dust formation. Numerical simulations are used to show the large and inhomogeneous changes of the gas phase chemistry in a turbulent dust forming cloud region of a brown dwarf atmosphere. The relaxation time scale of the gas phase composition towards steady state is considerably longer than for the dust component.

Galaxy interactions play an important role in the evolution of galaxies and triggering galaxy-wide star-formation or accretion onto nuclear black-holes. However, the strength and details of the relationship between galaxy interactions and triggered activity are still unclear. In order to address these questions we embarked on a Spitzer multi-wavelength study of a sample of nearby interacting galaxy systems. Our goal is to investigate: how interactions trigger star-formation by studying the spatial distribution and level of star-formation, and comparing them with theoretical models for different interaction parameters; how the interactions drive gas in the nuclear regions, and how this gas promotes and/or hides nuclear activity, by studying the distribution of dust and performing deep spectroscopic observations of the galactic nuclei; and how star-formation and AGN activity depend on the interaction stage.

One of the main goals of the Virtual Observatory activities right now is to provide the simple and powerful access to the large existing astronomical datasets in the VO compatible way. That is why we want present the results of the recent development of Sternberg Astronomical Institute Catalogue Access Services (SAI CAS) project – the first and the only project in Russia, which provides on-line access to the major astronomical catalogues and different services on top of them. It is developed by a group of astronomers in a framework of SAI Astronet project, funded by Russian Foundation for Basic Research. SAI CAS is an open-source implementation of the general Catalogue access service (influenced by SDSS CASjobs & OpenSkyQuery projects), based on original algorithms and open-source software. We decided to build our own system providing an effective access to the major astronomical catalogues and different services including cone-searches and cross-matching of user data with hosted catalogues.

In order to elucidate star formation in the Large Magellanic Cloud, a complete survey of the molecular clouds was carried out by NANTEN. In this work, we compare 230 giant molecular clouds (GMCs), whose physical quantities are well determined, with young clusters and Hii regions. We find that about 76% of the GMCs are actively forming stars or clusters, while 24% show no signs of massive star or cluster formation. Effects of supergiant shells (SGSs) on the formation of GMCs and stars are also studied. The number and surface mass densities of the GMCs are higher by a factor of 1.5–2 at the edge of the SGSs than elsewhere. It is also found that young stellar clusters are more actively formed in the GMCs facing to the center of the SGSs. These results are consistent with the previous studies by Yamaguchi et al. and suggest the formation of GMCs and the cluster is triggered by dynamical effects of the SGSs.

The signatures of intermittent dissipation of turbulent energy have been sought in the translucent environment of a low-mass dense core. Molecular line observations reveal a network of narrow filamentary structures, found on statistical grounds to be the locus of the largest velocity shears. Three independent properties of these structures make them the plausible sites of intermittent dissipation of turbulence: (1) gas there is warmer and more diluted than average, (2) it bears the signatures of a non-equilibrium chemistry triggered by impulsive heating due to turbulence dissipation, and (3) the power that these structures radiate in the gas cooling lines (mostly H2) is so large that it balances the total energy injection rate of the turbulent cascade, for a volume filling factor of only a few percents, consistent with other observations in the Solar Neighborhood. These filamentary structures may act as tiny seeds of gas condensation in diffuse molecular gas. They do not exhibit the properties of steady-state low-velocity magneto-hydrodynamic (MHD) shocks, as presently modelled.