We studied the formation process of star clusters using high-resolution N-body/smoothed particle hydrodynamics simulations of colliding galaxies. The total number of particles is 1.2×108 for our high resolution run. The gravitational softening is 5 pc and we allow gas to cool down to ~10 K. During the first encounter of the collision, a giant filament consists of cold and dense gas found between the progenitors by shock compression. A vigorous starburst took place in the filament, resulting in the formation of star clusters. The mass of these star clusters ranges from 105−8M⊙. These star clusters formed hierarchically: at first small star clusters formed, and then they merged via gravity, resulting in larger star clusters.

We present the spatially-resolved polarization measurements for the disk around the Herbig Ae star, AB Aurigae. The images were obtained in J, H, and Ks bands with the coronagraphic camera HiCIAO on the Subaru Telescope. The inner region beyond 30 AU from the star was imaged, which reveals an azimuthal dip, a radial gap at around 80 AU, and complex spiral-like emission in polarized light.

The interstellar medium (ISM) in galaxies is multiphase and cloudy, with stars forming in the very dense, cold gas found in Giant Molecular Clouds (GMCs). Simulating the evolution of an entire galaxy, however, is a computational problem which covers many orders of magnitude, so many simulations cannot reach densities high enough or temperatures low enough to resolve this multiphase nature. Therefore, the formation of GMCs is not captured and the resulting gas distribution is smooth, contrary to observations. We investigate how star formation (SF) proceeds in simulated galaxies when we obtain parsec-scale resolution and more successfully capture the multiphase ISM. Both major mergers and the accretion of cold gas via filaments are dominant contributors to a galaxy's total stellar budget and we examine SF at high resolution in both of these contexts.

We use a combination of VJHK and Spitzer [3.6], [5.8] and [8.0] photometry, to determine IR excesses in a sample of LMC and SMC O stars. This sample is ideal for determining excesses because: 1) the distances to the stars, and hence their luminosities, are well-determined, and; 2) the very small line of sight reddenings minimize the uncertainties introduced by extinction corrections. We find IR excesses much larger than expected from Vink et al. (2001) mass loss rates. This is in contrast to previous wind line analyses for many of the LMC stars which suggest mass loss rates much less than the Vink et al. predictions. Together, these results indicate that the winds of the LMC and SMC O stars are strongly structured (clumped).

Numerical 3D simulations of MHD waves in magnetized regions with background flows are very important for the understanding of propagation and transformation of waves in sunspots. Such simulations provide artificial data for testing and calibration of helioseismic techniques used for analysis of data from space missions SOHO/MDI, SDO/HMI, and HINODE. We compare with helioseismic observations results of numerical simulations of MHD waves in different models of sunspots. The simulations of waves excited by a localized source provide a detailed picture of the interaction of the MHD waves with the magnetic field and background flows (deformation of the waveform, wave transformation, amplitude variations and anisotropy). The observed cross-covariance function represents an effective Green's function of helioseismic waves. As an initial step, we compare it with simulations of waves generated by a localized source. More thorough analysis implies using multiple sources and comparison of the observed and simulated cross-covariance functions. We plan to do such calculations in the nearest future. Both, the simulations and observations show that the wavefront inside the sunspot travels ahead of a reference “quiet Sun” wavefront, when the wave enters the sunspot. However, when the wave passes the sunspot, the time lag between the wavefronts becomes unnoticeable.

We present results of a broadband spectroscopy of the galactic microquasars and black hole candidates XTE J1550-564 and GRO J1655-40, performed with the INTEGRAL and RXTE observatories during strong outbursts in 2003 and 2005, respectively. The spectral parameters evolution was traced during brightening and fading phases of each outburst to search a possible hysteresis and transitions from state to state. We estimated a size and optical depth of different regions around XTE J1550-564, like a hot plasma zone and optically thick accretion disk. Upper limits to the annihilation 511 keV line emission were obtained for both sources using data of the SPI spectrometer onboard the INTEGRAL observatory.

The fractal shape and multi-component nature of the interstellar medium together with its vast range of dynamical scales provides one of the great challenges in theoretical and numerical astrophysics. Here we will review recent progress in the direct modelling of interstellar hydromagnetic turbulence, focusing on the role of energy injection by supernova explosions. The implications for dynamo theory will be discussed in the context of the mean-field approach.

Results obtained with the test field-method are confronted with analytical predictions and estimates from quasilinear theory. The simulation results enforce the classical understanding of a turbulent Galactic dynamo and, more importantly, yield new quantitative insights. The derived scaling relations enable confident global mean-field modelling.

We have analysed very high-quality HARPS and UVES spectra of 95 solar analogs, 24 hosting planets and 71 without detected planets, to search for any possible signature of terrestial planets in the chemical abundances of volatile and refractory elements with respect to the solar abundances.

We demonstrate that stars with and without planets in this sample show similar mean abundance ratios, in particular, a sub-sample of 14 planet-host and 14 “single” solar analogs in the metallicity range 0.14 < [Fe/H] < 0.36. In addition, two of the planetary systems in this sub-sample, containing each of them a super-Earth-like planet with masses in the range ~ 7-11 Earth masses, have different volatile-to-refratory abundance ratios to what would be expected from the presence of a terrestial planets.

Finally, we check that after removing the Galactic chemical evolution effects any possible difference in mean abundances, with respect to solar values, of refratory and volatile elements practically dissappears.

Creation of a modern database with a wide variety of data is an important step toward a better understanding of the Be phenomenon. In an effort to do that, I refined the existing catalog of Galactic Be stars and collected available observational data for 340 brightest objects and present some results of these data analysis. New candidates for Be binaries, which seem to represent a large fraction of Be stars, are suggested. Importance of the circumstellar optical continuum for modeling of the Be star envelopes is illustrated.

Major progress has been made over the last few years in understanding hydrodynamical processes on cosmological scales, in particular how galaxies get their baryons. There is increasing recognition that a large part of the baryons accrete smoothly onto galaxies, and that internal evolution processes play a major role in shaping galaxies – mergers are not necessarily the dominant process. However, predictions from the various assembly mechanisms are still in large disagreement with the observed properties of galaxies in the nearby Universe. Small-scale processes have a major impact on the global evolution of galaxies over a Hubble time and the usual sub-grid models account for them in a far too uncertain way. Understanding when, where and at which rate galaxies formed their stars becomes crucial to understand the formation of galaxy populations. I discuss recent improvements and current limitations in “resolved” modeling of star formation, aiming at explicitly capturing star-forming instabilities, in cosmological and galaxy-sized simulations. Such models need to develop three-dimensional turbulence in the ISM, which requires parsec-scale resolution at redshift zero.

The X-ray transient source XTE J1818–245 went through an outburst in 2005 that was observed during a multi-wavelength campaign from radio to soft γ-rays. We performed new optical observations with the ESO/NTT telescope at La Silla. The broad-band spectral energy distribution revealed that the outer parts of the accretion disc had to be irradiated by its inner parts to explain the optical emission.

We present recent developments of global galactic-scale numerical models of the Cosmic Ray (CR) driven dynamo, which was originally proposed by Parker (1992). We conduct a series of direct CR+MHD numerical simulations of the dynamics of the interstellar medium (ISM), composed of gas, magnetic fields and CR components. We take into account CRs accelerated in randomly distributed supernova (SN) remnants, and assume that SNe deposit small-scale, randomly oriented, dipolar magnetic fields into the ISM. The amplification timescale of the large-scale magnetic field resulting from the CR-driven dynamo is comparable to the galactic rotation period. The process efficiently converts small-scale magnetic fields of SN-remnants into galactic-scale magnetic fields. The resulting magnetic field structure resembles the X-shaped magnetic fields observed in edge-on galaxies.

Today's Solar Physics comes across of different type of fine structures in solar atmosphere including umbral dots and penumbral grains in sunspots, and G-band bright points in quiet Sun. In this report, we present evidence that umbral dots, penumbral grains, and, possibly, G band bright points are related to a common type of features in solar atmosphere magnetic flux tubes.

We report results from numerical simulations of star formation in the early universe that focus on the role of subsonic turbulence, and investigate whether it can induce fragmentation of the gas. We find that dense primordial gas is highly susceptible to fragmentation, even for rms turbulent velocity dispersions as low as 20% of the initial sound speed. The resulting fragments cover over two orders of magnitude in mass, ranging from ~0.1 M⊙ to ~40 M⊙. However, our results suggest that the details of the fragmentation depend on the local properties of the turbulent velocity field and hence we expect considerable variations in the resulting stellar mass spectrum in different halos.

We propose that at the beginning of the Maunder minimum the poloidal field or amplitude of meridional circulation or both fell abruptly to low values. With this proposition, a flux transport dynamo model is able to reproduce various important aspects of the historical records of the Maunder minimum remarkably well.

The e-MERLIN Cyg OB2 Radio Survey (COBRaS) is designed to exploit e-MERLIN's enhanced capabilities to conduct uniquely probing, targeted deep-field mapping of the massive Cyg OB2 association in our Galaxy. The project aims to deliver (between 2010 to 2013) the most detailed radio census for the most massive OB association in the northern hemisphere, offering direct comparison to not only massive clusters in general, but also young globular clusters and super star clusters. With the COBRaS Legacy project we will assemble a uniform dataset of lasting value that is critical for advancing our understanding of current astrophysical problems in the inter-related core themes of (i) mass loss and evolution of massive stars, (ii) the formation, dynamics and content of massive OB associations, and (iii) the frequency of massive binaries and the incidence of non-thermal radiation.

We present discovery of a radio nebula associated with the ultraluminous X-ray source (ULX) IC 342 X-1 using the Very Large Array (VLA). Taking the surrounding nebula as a calorimeter, one can constrain the intrinsic power of the ULX source. We compare the obtained power that is needed to supply the radio nebula with the W50 nebula powered by the microquasar SS433 and with other ULXs. We find that the power required is at least two orders of magnitude greater than that needed to power radio emission from the W50 nebula associated with the microquasar SS433. In addition, we report the detection of a compact radio core at the location of the X-ray source.

Planet formation theory is founded on the concept of dust coagulation and subsequent growth into planetesimals. This process is by no means an isolated one, but possibly happens in a turbulent nebula. It is therefore crucial to understand how particles of different sizes are affected by their gaseous environment via stochastic forcing and aerodynamic damping. We here report on the effects of magneto-rotational (MRI) turbulence in the presence of non-uniform ionisation leading to the formation of a magnetically inactive dead-zone. While we find that collisional growth is impeded by fully-active MRI, it may be possible within a dead-zone.