Graduate Program in Astrophysics in Split

Beginning in autumn 2008 the first generation of astronomy master students will start a 2 year course in Astrophysics offered by the Physics department of the University of Split, Croatia (http://fizika.pmfst.hr/astro/english/index.html). This unique master course in South-Eastern Europe, following the Bologna convention and given by astronomers from international institutions, offers a series of comprehensive lectures designed to greatly enhance students' knowledge and skills in astrophysics, and prepare them for a scientific career. An equally important aim of the course is to recognise the areas in which astronomy and astrophysics can serve as a national asset and to use them to prepare young people for real life challenges, enabling graduates to enter the modern society as a skilled and attractive work-force. In this contribution, I present an example of a successful organisation of international astrophysics studies in a developing country, which aims to become a leading graduate program in astrophysics in the broader region. I will focus on the benefits of the project showing why and in what way astronomy can be interesting for third world countries, what are the benefits for the individual students, nation and region, but also research, science and the astronomical community in general.Comment: proceedings of IAU SpS5, Astronomy for the Developing world, eds. J. Hearnshaw & P. Martine

Large Eddy Simulation Exploration of Passive Flow Control Around an Ahmed Body

Large eddy simulations (LES) are used to study passive flow control for drag reduction in a simplified ground vehicle. Add-on devices in the form of short cylinders are used for the formation of streaks in the streamwise direction that lead to the separation delay. The results of the present numerical simulations are compared with the experimental data and show good agreement. The two-stage flow control mechanism is analyzed from the LES results. It was found to be in agreement with the previous experimental observations that the counter-rotating vortices behind the impinging devices influence the separation only indirectly through the longitudinal vortices further downstream

Kinemetry: a generalisation of photometry to the higher moments of the line-of-sight velocity distribution

We present a generalisation of surface photometry to the higher-order moments of the line-of-sight velocity distribution of galaxies observed with integral-field spectrographs. The generalisation follows the approach of surface photometry by determining the best fitting ellipses along which the profiles of the moments can be extracted and analysed by means of harmonic expansion. The assumption for the odd moments (e.g. mean velocity) is that the profile along an ellipse satisfies a simple cosine law. The assumption for the even moments (e.g velocity dispersion) is that the profile is constant, as it is used in surface photometry. We find that velocity profiles extracted along ellipses of early-type galaxies are well represented by the simple cosine law (with 2% accuracy), while possible deviations are carried in the fifth harmonic term which is sensitive to the existence of multiple kinematic components, and has some analogy to the shape parameter of photometry. We compare the properties of the kinematic and photometric ellipses and find that they are often very similar. Finally, we offer a characterisation of the main velocity structures based only on the kinemetric parameters which can be used to quantify the features in velocity maps (abridged).Comment: 17 pages, 11 figures. MNRAS in press. High resolution version of the paper is available at http://www.strw.leidenuniv.nl/sauron/papers/krajnovic2005_kinemetry.pdf and software implementation of the method is freely available at http://www-astro.physics.ox.ac.uk/~dxk/idl

Measuring the low mass end of the Mbh - sigma relation

We show that high quality laser guide star (LGS) adaptive optics (AO) observations of nearby early-type galaxies are possible when the tip-tilt correction is done by guiding on nuclei while the focus compensation due to the changing distance to the sodium layer is made 'open loop'. We achieve corrections such that 40% of flux comes from R<0.2 arcsec. To measure a black hole mass (Mbh) one needs integral field observations of both high spatial resolution and large field of view. With these data it is possible to determine the lower limit to Mbh even if the spatial resolution of the observations are up to a few times larger than the sphere of influence of the black hole.Comment: 4 pages, 2 figures, LaTeX. To appear in "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P. Debattista and C.C. Popescu, AIP Conf. Ser., in pres

The flow around a simplified tractor-trailer model studied by large eddy simulation

Large-eddy simulation (LES) is used to study the flow around a simplified tractor-trailer model. The model consists of two boxes placed in tandem. The front box represents the cab of a tractor-trailer road vehicle and the rear box represents the trailer. The LES was made at the Reynolds number of 0.51×106 based on the height of the rear box and the inlet air velocity. Two variants of the model were studied, one where the leading edges on the front box are sharp and one where the edges are rounded. One small and one large gap width between the two boxes were studied for both variants. Two computational grids were used in the LES simulations and a comparison was made with available experimental force measurements. The results of the LES simulations were used to analyze the flow field around the cab and in the gap between the two boxes of the tractor-trailer model. Large vortical structures around the front box and in the gap were identified. The flow field analysis showed how these large vortical structures are responsible for the difference in the drag force for the model that arises when the leading edges on the front box are rounded and the gap width is varied

Simulations of flow around a simplified train model with a drag reducing device

Partially Averaged Navier Stokes is used to simulate the flow around a simple train model. The train model has previously been studied in wind tunnel experiments and has a length to height/width ratio of 7:1. The Reynolds number based on the height of the train model is 0.37 x 10^6. For this Reynolds number, the flow separates from the curved leading edges on the front then attaches again on the roof and sides forming a boundary layer there before separating in the wake. The first case is of the natural flow around the train model where direct comparison to experimental data of drag coefficient and pressure coefficient are made. In the second case an open cavity is placed on the base of the train model with the aim of reducing the overall drag on the model. The results show that the drag for model with the cavity is reduced by some 10% compared to the drag of the natural case. The agreement to experimental data for the natural case is not perfect but the general features in the flow field are simulated correctly

A way to deal with the fringe-like pattern in VIMOS-IFU data

The use of integral field units is now commonplace at all major observatories offering efficient means of obtaining spectral as well as imaging information at the same time. IFU instrument designs are complex and spectral images have typically highly condensed formats, therefore presenting challenges for the IFU data reduction pipelines. In the case of the VLT VIMOS-IFU, a fringe-like pattern affecting the spectra well into the optical and blue wavelength regime as well as artificial intensity variations, require additional reduction steps beyond standard pipeline processing. In this research note we propose an empirical method for the removal of the fringe-like pattern in the spectral domain and the intensity variations in the imaging domain. We also demonstrate the potential consequences for data analysis if the effects are not corrected. Here we use the example of deriving stellar velocity, velocity dispersion and absorption line-strength maps for early-type galaxies. We derive for each spectrum, reduced by the ESO standard VIMOS pipeline, a correction-spectrum by using the median of the eight surrounding spectra as a proxy for the unaffected, underlying spectrum. This method relies on the fact that our science targets (nearby ETGs) cover the complete FoV of the VIMOS-IFU with slowly varying spectral properties and that the exact shape of the fringe-like pattern is nearly independent and highly variable between neighboring spatial positions. We find that the proposed correction methods for the removal of the fringe-like pattern and the intensity variations in VIMOS-IFU data-cubes are suitable to allow for meaningful data analysis in our sample of nearby early-type galaxies. Since the method relies on the scientific target properties it is not suitable for general implementation in the pipeline software for VIMOS.Comment: 7 pages, 10 figures, accepted for publication in A&A, new version after comments from language edito