Research Areas

Massive stars have a strong influence on the appearance of galaxies: with their strong outflows during their formation, their winds and UV radiation and, at the end of their lifes, powerful supernova explosions. In spite of their importance, much less is known about their process of formation than for their lower mass, sun-like siblings. Using teleccopes operating at a large range of wavelenghts (e.g. at cm-wavelengths using Effelsberg, and mm-wavelengths using the IRAM 30m and NOEMA telescopes and at submm-wavelenghts using APEX, ALMA and SOFIA) many aspects of star formation are studied, [more]
Molecules allow us to probe the physical properties of the interstellar medium, such as its temperature, density, and kinematics, or the radiation field and cosmic rays that impinge on it. They also reveal the chemical composition of astronomical environments, in particular star forming regions. This chemical composition is a powerful tool to probe the history of these regions and reveal their evolutionary stage. Studying this chemical composition across the phases of star formation tells us about the inheritance or reprocessing of the outcome of interstellar chemistry from the earliest stages (molecular cloud cores prior to the formation of stars) to the latest ones (circumstellar disks where planets form and life may appear). [more]
The Milky Way is a barred spiral galaxy, as seen from observations of CO and HI gas, and star counts. However, our location in the Galaxy makes it difficult to determine the number and positions of spiral arms, the extent and orientation of the central bar, and the Galaxy's rotation curve. As a result, even the most fundamental parameters of the Milky Way, such as the distance to the Galactic center, R0, and the rotation speed, Î0, are still not known with high accuracy. These values are not only important for Galactic astronomy, but also for a wide range of different fields. In recent years, many large scale surveys have covered the Galactic Plane in all wave bands from radio to gamma rays. All of these surveys are two dimensional, and using them to construct a three dimensional model of the Milky Way is not trivial, mainly due to large uncertainties in distance measurements. These uncertainties also affect the interpretation of these surveys, since most astrophysical quantities, such as linear size, mass, and luminosities, strongly depend on the distance to the object. [more]
The physics and chemistry of the circumstellar envelopes (CSEs) around evolved stars have much in common with the dense(r) ISM: in both areas, observations of the emission from molecules provide key information. We have investigated a range of interesting topics related to the chemistry of oxygen-rich and carbon-rich asymptotic giant branch stars. In particular, with ALMA and the VLA we have resolved their innermost regions and even resolved their photospheres. We started investigations of planetary nebulae in atomic fine structure and molecular lines with SOFIA and for the first time discovered the long-sought HeH + ion in one of them. [more]
The evolution of galaxies is largely driven not only by how stars form, but also by the way in which star formation ends. The “star formation quenching'', that accompanies the transformation of a blue spiral into a red elliptical galaxy, can be caused by a variety of phenomena connected to removal, reduction, or stabilisation of the star formation raw fuel: the cold gas.

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