"Signposts of evolved planetary systems"

Boris GAENSICKE (Warwick university, UK)

Abstract

The strong surface gravity of white dwarfs implies that metals will sink out of the photosphere on time-scales that are orders of magnitude shorter than their cooling ages, and therefore white dwarfs are expected to have either pure hydrogen or helium atmospheres. Yet, the existence of metal-polluted white dwarfs has been a conundrum for nearly a century. We know now that these white dwarfs are polluted by accretion of rocky debris, remnants of a former planetary system. With hindsight, this is may not come as too much of a surprise, as our Sun will eventually evolve in a white dwarf orbited by Mars, the outer planets, and hosts of asteroids - and a similar fate awaits many of the known exo-planetary systems! State-of-the art model atmosphere analyses of high-resolution (Keck/VLT/HST) spectra of white dwarfs demonstrate that the bulk composition of the circumstellar debris is overall similar to that of the terrestrial planets in the Solar system, yet there is evidence for a variety of thermal processing and possibly differentiation in the parent bodies. Perhaps most astonishing are the lower limits on the mass of the parent bodies that were accreted, ranging up to 1e24g, i.e. well above the most massive asteroids in the Solar system. These chemical abundance analyses are currently, and for some time to come, by far the most precise studies of extra-solar planetary material.

"Galaxy Interactions in Compact Groups : The Galactic Winds of HCG16"

Frédéric VOGT (Mount Stromlo Observatory, Australia)

Abstract

In my PhD, I have undertaken a series of observations of star-forming galaxies in Compact Groups (CGs) with the WiFeS integral field spectrograph. This project investigates the physics of galaxy interactions, the formation of galactic winds, and the onset of star formation episodes in a CG environment. In this presentation, I will present the first outcome of this project: the analysis of the galactic wind of NGC838 in HCG16, an asymmetric, bipolar, rotating structure, powered by a nuclear starburst. I will then compare this wind with the neighbouring wind in NGC839, which gives us clues regarding galactic winds formation mechanisms and the group interaction history.

"Multiple stellar-mass black holes in globular clusters"

Anna SIPPEL (ESO, Chile)

Abstract

While tens or hundreds of stellar-remnant black holes are expected to form in globular star clusters, it is still unclear how many of those will be retained upon formation, and how many will be ejected through subsequent dynamical interactions. No such black holes have been found in any Milky Way globular cluster until the recent discovery of stellar-mass black holes in M22. I present a direct N-body model of a star cluster similar to M22. Multiple stellar-remnant black holes are retained at a cluster age of 12 Gyr and I illustrate the dynamical history of the black hole population in this model. This will show that multiple black holes could be present in any Milky Way globular cluster with an extended core (as it is the case for M22 or the N-body model presented here).

"The solution of the Fundamental Plane problem"

Mauro D'ONOFRIO (University of Padova, Italy)

Abstract

We show that the fine-tuning between stellar structure and population is the key to understand the FP tilt and tightness. In particular we demonstrate that the relations between the Sersic index n, the mass of the galaxies M* and the mass-to-light ratio M*/L (nMML relation), is just the fine-tuning the produces most of the observed tilt. On the other hand, stellar population variation cannot account of the bulk of the tilt, but only of the differential tilt observed at the various wavelengths.