Wednesday Colloquium


"Where gravity no longer dominates: the internal structure and evolution of the smallest asteroids"

Tomasz Kwiatkowski (Poznan Observatory, A.Mickiewicz University)

Asteroids are very diverse in composition. While the largest of them are spheroidal bodies, and the middle-sized ones are gravity-dominated, irregular rubble-piles, the smallest asteroids are boulders held together by the forces of cohesion. Observations suggest that the last named can be surpisingly weak bodies evolving under the infuence of the YORP effect.


"Understanding formation of supermassive black holes"

Isaac Shlosman (Department of Physics and Astronomy, University of Kentucky, Lexington)

Little is known but much is speculated about how when and where supermassive black holes form. With the detection of high redshift quasars, this issue was brought to the forefront and has been tied to Population III stars and to galaxy formation process. In my talk, I will review some options and discuss promissing leads to understand the formation of these enigmatic objects.


"Spin and Spine"

Rien Van De Weygaert (Kapteyn Institute, Groningen)

With the help of our Multiscale Morphology Filter we have searched for significant alignments of the spin of galaxies with respect to filaments in the Cosmic Web. Such alignments are a direct manifestation of large-scale tidal fields morphing the weblike large scale structure as well as the tidal torques spinning up dark halos. Instead of an orientation correlation study, we have chosen to identify the galaxies that carry the most significant fossil alignment in the cosmic Web. By restricting the analysis of the SDSS DR5 galaxy sample to edge-on galaxies, we guarantee a perfect and clean orientation signal. Following a local and individual statistical analysis based on three feature measures, we have found a significant signal of alignment. From our sample, we can point to fourteen galaxies that have an uncommon perpendilar orientation with respect to the filaments in which they are embedded.


"On the transition from radio-loud to radio-quiet state in quasars in the framework of the XRB versus AGN unification"

Andrzej Marecki (Centre for Astronomy, N. Copernicus University, Toruń)

There are several lines of evidence that active galactic nuclei can be regarded as scaled-up X-ray binaries (XRB). The timescales of the evolutionary phenomena in these two classes are proportional to the black hole masses. Consequently, unlike in the case of XRBs, the evolution of AGNs is too slow to be followed directly. What could be done, however, is to assign particular types of active galaxies to different evolutionary stages observable in XRBs. We found three quasars with clear signatures of a recent transition from radio-loud to radio-quiet state and our own observations confirmed that, despite conspicuous relic large-scale radio structures, their cores can be labelled radio-quiet, anyway. It looks, therefore, that these objects were in the so-called Very High state before and now have shifted to High-Soft state. Analogous transitions in XRBs are well known.