Wednesday Colloquium



Łukasz Wyrzykowski (Astronomical Observatory, Warsaw University)


"Physics after the discovery of the Higgs particle"

Jan Kalinowski (Institute for Theoretical Physics, Warsaw University)


"Variable stars related to the X-ray sources"

Marcin Kiraga (Astronomical Observatory, Warsaw University)

Photometric data from the ASAS survey are used for the search for variable stars related to ROSAT X-ray sources. There are more than 3600 stars found so far. The main variability types are rotationally variable stars due to presence of spots and eclipsing binaries. Most of them have X-ray emission of coronal origin, there are a few cataclysmic binaries and early type binaries with colliding winds. We present some interesting variable stars and rotation period - X-ray activity relation for magnetically active stars.


"Through the eye of SAURON: evolution of dwarf elliptical galaxies in the Virgo cluster"

Agnieszka Ryś (ESO, Garching)

Dwarf elliptical galaxies (dEs) are the most common galaxy class in dense environments, outnumbering all other classes combined. Their low masses make them ideal test beds for studying different mechanisms that shape galaxies, since both external influences and internal feedback mechanisms are far more extreme in dwarfs than in massive galaxies. dEs are a surprisingly inhomogeneous class, which has made it difficult to relate different dE subtypes to each other, as well as to place the whole class in the larger context of galaxy assembly and (trans)formation processes. Here I will present the kinematic, dynamical and stellar population analysis of a sample of 12 dEs observed using the SAURON integral-field unit mounted on the 4.2m William Herschel Telescope (ORM, La Palma). We have obtained large-scale two-dimensional maps of kinematic and stellar population properties for objects for which (with very few and small-scale exceptions) only one-dimensional profiles were available before. From the variety of dE properties we find and confirm with our data, and through their analysis, we are able to show tidal harassment signatures in the galaxies' dynamical and stellar population properties, paying particular attention to radial trends within the cluster. We can thus establish dE progenitor class with more accuracy and define the place of dEs among other galaxy types.