Gas and dust structure and nuclear star formation
The quiescent nucleus of the Milky Way
The nucleus of the Andromeda Galaxy
The G2 cloud
We study the characteristics of turbulence
in AGN tori, stirred by discrete energy
input mechanisms like supernova
explosions or stellar winds and determine
the timescales of the decay of the
thickness of the resulting density
distribution. Below, a cut along a
meridional plane is displayed after 10 orbits.
This study will show us, whether long term
stirring processes are needed.
A molecular cloud is put into the potential of a
supermassive black hole. We study
disruption, disk-phase and fragmentation.
Such a scenario might lead to a stellar
disk, as seen in our own galactic center.
The picture shows the capturing of a
cloud of 10^5 solar masses after 0.5
Myrs by a black hole of 10^6 solar masses.
We are studying stellar winds for a large range of ambient densities and
pressures. Understanding the evolution and interaction of winds,
particularly for high pressure external media, will help us in finding a
plausible origin for the G2 cloud observed in the Galactic center, as well
as in explaining the clumpy and turbulent structure of AGN tori.
Young disk galaxies have recently been observed at high cosmological redshifts of z=2,
corresponding to epochs where the Universe was just 1/3rd its present age. This epoch is especially
interesting as it corresponds to the peak in the star formation rate of the Cosmos and the time when
the morphologies of the galaxies were determined. High-redshift galaxies have recently been
detected and observed with the larges telescopes e.g. of ESO. It soon became clear that these
objects are very different compared with present-day disk galaxies. For example, they form stars
with enormous rates that are a factor of 10 - 100 higher than in nowadays. The star formation is
concentrated in gigantic clumps of molecular gas, about 1000 times larger than present-day
molecular clouds, and as big as dwarf galaxies. In addition, the gas in the disks is highly turbulent,
driven by energetic sources that are not well understood up to now. In collaboration with the
observational infrared/submillimeter group we are investigating the origin and structure of the
observed giant gas clumps in young galactic disks as well as their evolution and star formation
The principal part of my research involves modelling galaxies to understand how giant molecular clouds (GMCs), the sites of star formation in galaxies, form and evolve. The main difficulty with studying star formation in galaxies is the immense range in scales between galaxies and stars. Much of the research in astrophysics concerns the formation of stars in molecular clouds However this misses out the physics of how GMCs form, as governed by large scale processes such as spiral shocks, self gravity and stellar feedback. This is what I work on. I have also done research into spiral structure in galaxies, in particular showing how even detailed features in the famous Whirlpool Galaxy (M51) are reproduced by its interaction with a companion.
We calculate black hole growth rates,
based on merger trees from
cosmological dark matter simulations
with the GADGET-2 code. These will
be confronted with the observed
quasar luminosity evolution (quasar downsizing).
Radiation from AGN might drive turbulence within the torus, which
could keep it thick. We aim to perform 3D hydrodynamic
simulations with radiative transfer to address this. The example
gives an impression how a density slice looks like, and an
integration of the total optical depth due to hydrogen and dust
extinction at a wavelength just shortward of the Lyman edge.
Physics of the Interstellar Medium SPP
Physics of Galactic Nuclei Group
University Observatory Munich
Excellence Cluster Munich