Recent Talks

Up to now more than 400 extrasolar planets have been discovered, about 60 of them are transiting. Transiting extra-solar planets are particularly interesting, because their masses, diameters, densities and orientations of their orbits can be determined. Observations with the CoRoT Satellite have now turned up 10 transiting extrasolar planets. Although most of them are gas giants, it turns out that each of them is very special, and many of them have surprising properties. An unexpected discovery was for example the detection of emission lines from CoRoT 1b. Other interesting discoveries are CoRoT 2b, a planet orbiting a young star, and CoRoT 3b the first transiting brown dwarf orbiting a main sequence star. While the detection of transiting gas giants is interesting, the ultimate goal of CoRoT clearly was the detection of rocky planets. CoRoT has detected a solar-like star which shows transits that are only 0.03% deep. In this talk it it is demonstrated that this planet is in fact the first planet found outside our solar system from which we can firmly say that it is a rocky planet. New observations of this interesting object even constrain the properties of its exosphere.

There are many parameters accounting for the quality of an astronomical site, namely seeing, cloud cover, ground winds, high-altitude winds, etc. The water vapor content is the main parameter affecting the IR quality of astronomical sites. The fraction of nights with good IR conditions (small column of water vapor) as a function of the epoch of the year will allow an optimal scheduling of telescope observing time. Global Positioning System (GPS) is an increasingly operational tool for measuring the precipitable water vapor (PWV). In this seminar, we briefly describe the procedure to estimate the PWV through GPS and we present the statistical results derived from a 7.5-year long time series of PWV estimations derived from GPS at the Roque de los Muchachos Observatory.

Luminous high-redshift radio galaxies (HzRGs) are associated with the most massive known galaxies in the early Universe. These galaxies have the properties expected of the progenitors of dominant galaxies in rich clusters.
I shall describe the properties of HzRGs and demonstrate how they can be used to study the formation and evolution of galaxies and clusters. I shall also show how LOFAR, the new European radio telescope, can be used to extend these probes into the epoch of reionisation.

We test the theoretical prediction that the straightest dust lanes in bars are found in strongly barred galaxies, or more specifically, that the degree of curvature of the dust lanes is inversely proportional to the strength of the bar. The test uses archival images of barred galaxies for which a reliable non-axisymmetric torque parameter (Q_b) and the radius at which Q_b has been measured (r(Q_b)) have been published in the literature. Our results confirm the theoretical prediction but show a large spread that cannot be accounted for by measurement errors. We simulate 238 galaxies with different bar and bulge parameters in order to investigate the origin of the spread in the dust lane curvature versus Q_b relation. From these simulations, we conclude that the spread is greatly reduced when describing the bar strength as a linear combination of the bar parameters Q_b and the quotient of the major and minor axes of the bar, a/b. Thus, we conclude that the dust lane curvature is predominantly determined by the parameters of the bar.