Astrophysics at the University of Vienna

Research and teaching in astronomy and astrophysics at the University of Vienna can be traced back to the second half of the 14th century. The present-day institute building - the current university observatory - was opened in 1883. It still harbours Austria's largest astronomical research and teaching facility.

Our central research areas are the formation and evolution of galaxies, stars and planets. Using the latest ESO, ESA and NASA telescopes and satellites, as well as powerful computers,we investigate a manifold of processes of structure formation in the universe - from clusters of galaxies to the scale of planetary systems. The main areas of research and instrument development are the following:

Observational extragalactic astrophysics (Prof. Bodo Ziegler et al.)

The first galaxies were formed as early as 500 million years after the Big Bang. In the 13 billion years since then, they have changed their shape and composition repeatedly, but also new galaxies were formed. In order to advance our understanding of the universe, one must look at its entire development, from our Milky Way all the way back to the first galaxies.This is not only dependent on the processes of star formation, but on all physical aspects of the evolution of galaxies. In order to study these, one has to examine galaxies with many different approaches in all wavelength ranges – X-rays, visible light, infrared radiation and radio waves: a multi-wavelength approach.

The researchers predominantly use spectroscopic methods to determine the physical properties of galaxies.Bodo Ziegler’s team participated in the international project CALIFA (Calar Alto Legacy Integral Field Area) that observed more than 600 very different galaxies in our Galactic neighbourhood at the Calar Alto observatory in southern Spain over three years using a special 3D-spectroscopic method. This new method allowed them to distinguish on spatially resolved scales the physical properties, such as their kinematic characteristics, their chemical composition and their stellar populations more precisely than ever before. In another project, Ziegler and his team observe galaxies that are between 5 and 8 billion light years away. The focus is on potential interactions between galaxies clustered closely together. For their analysis, they combine spectroscopy using the largest telescopes of ESO (of which Austria is a member) located in Chile’s Atacama Desert and high-quality imaging from the Hubble Space Telescope.

Interstellar medium and star formation (Prof. João Alves et al.)

How do diffuse interstellar gas clouds form, evolve and eventually collapse to form stars and planets? This is the key research question of João Alves and his research group. To see through the interstellar gas clouds, Alves and his research group primarily use infrared telescopes such as Herschel and ESO’s Very Large Telescope.

One of the Group’s key research areas is the 3-D visualisation of data from space. Their 3-D analyses recently uncovered an optical illusion that had not been detected with the previous 2-D analyses: The Gould Belt in the Milky Way is not actually a ring of stars but a projection effect. This puts the existence of the “belt” of stars near our Sun, which was first identified in the 19th century, into question. As part of the international project, the researchers also created the first 3-D map of the regions around our Sun. Their 3-D analysis also revealed the presence of enormous streams of young stars, traced by the massive but short-lived O- and B-stars. The data came from the European Space Agency (ESA) satellite Hipparcos.

Alves’ Group is also involved in the Gaia satellite project of ESA and will explore Gaia data with the new 3-D techniques developed for the Hipparcos satellite.The data will allow them to reconstruct the regions near our Sun in a never before seen resolution and create accurate maps of stars and the interstellar gas between them.They will be able not only to reconstruct our galactic neighbourhood accurately but, by doing that, understand the origins of sun-like stars and the build-up of galaxies like our Milky Way. (now already Data Release 2)

NFN "Conditions for habitable planets" and working group "Star and Planet Formation" (Prof. Manuel Güdel et al.)

The question why life is possible on Earth and not on some other planets is the focus of Manuel Güdel and his Research Group Star and Planet Formation. Co-operating with researchers from other groups and departments, Güdel is studying the astrophysical factors that make planets habitable.

He heads a national research network, for which the Austrian Science Fund (FWF) provides funding until 2020. How do the properties of stars influence planets? Under what conditions do some proto-atmospheres survive on planets, and why do some evaporate? What properties must a planet have to create suitable conditions for life and, in particular, liquid water? And how do all these factors have to interact to finally result in a habitable planet? Their goal is to gain a comprehensive view of the different factors and their interactions using modelling. His team is initially focusing on our solar system – particularly Earth with its neighbours Mars and Venus – as a field of study. In the case of Earth, its mass, insolation and the astronomical architecture of our solar system made life possible. However, the group is also studying extrasolar planetary systems with very different properties.

In another project, Güdel’s group is studying the properties of so-called protoplanetary disks – enormous disks of gas and dust that can later form planets. It is important to understand protoplanetary disks in order to understand where planets come from, how they form, grow and create their first atmosphere. The project is funded by the EU, the FWF and the Austrian Research Promotion Agency (FFG).

At the same time, Güdel’s group and other researchers at the Department of Astrophysics are involved in a number of space missions.

Dynamics of Stellar Systems (Prof. Glenn van de Ven et al.)

The research group led by Prof. Glenn van de Ven focuses on understanding the structure and evolution of nearby galaxies and stellar clusters. They construct advanced dynamical models to infer the luminous and dark matter distribution in these stellar systems, as well as to uncover the 'fossil record' of their formation history.

Schwarzschild’s orbit-superposition method is a powerful technique which the research group has employed to build intricate dynamical models of hundreds of nearby spiral to elliptical galaxies. By fitting the stellar and gas motions extracted from (integral-field) spectroscopy of these galaxies, they succeeded in unveiling their intrinsic components like dynamically hot bulges, warm thick discs and cold thin discs, as well as accreted components in 6D phase-space. The research group is developing a new code DYNAMITE – DYNamics Age and Metallicity Indicators Tracing Evolution – which additionally tags the orbits with stellar population properties like age and metallicity to enhance the recovery of galaxy components and simultaneously trace back their formation history.

Complementary to the stars and gas in galaxies, the research group aims to unlock the full potential of “globular clusters as living fossils of the past of galaxies” within the ERC-funded project ArcheoDyn. Globular clusters are compact stellar systems of around a million stars which can be observed out to large distances surrounding galaxies. Since globular clusters are typically as old as the Universe, they are thus surviving witnesses to the formation history of their host galaxies.

The research group members have been and are active in a number of international collaborations such as the SAURON Project, CALIFA Survey, Fornax Deep Survey, Fornax 3D Survey. By organising conferences and workshops on a variety of topics, the group is actively connecting fellow researchers and supporting content-related exchange on an international level.

Late stages of stellar evolution (Prof. Franz Kerschbaum et al.)

Sun-like stars become pulsating red giants in their late evolutionary stages (also called AGB stars). The red giants are characterised by expanding gas and dust envelopes, which enrich the interstellar space with heavy elements and solids.

This process provides the raw material for star and planet formation. In the working group led by Franz Kerschbaum and Josef Hron, questions like the following are being investigated: What drives the stellar winds of red giants? How can we understand the structure and composition of the extended star shells? What is the composition of the dust shells that form with up to several earth masses per year? Latest techniques such as interferometry with the VLT and the ESO radio telescope ALMA as well as space telescopes help us to find answers to the questions asked.

Space Instrumentation (Prof. Franz Kerschbaum et al.)

In order to conduct astronomical observations with space based instruments, a number of special conditions need to be met. For this reason, different groups have been involved in the development of a number of space-based telescopes such as CoRoT, MOST, GAIA and Herschel, as well as in the development of relevant data reduction procedures.

Currently, the institute is involved in future space missions such as CHEOPS, SMILE, PLATO, EUCLID, ATHENA and SPICA.

The institute also developed the first Austrian satellite, BRITE, in collaboration with the Space Flight Laboratory of the University of Toronto in Canada and the Graz University of Technology. The launch took place in February 2013.

Instrumentation for terrestrial observatories

A number of Austrian scientists are involved in the development of three instruments for the European Extremely Large Telescope (E-ELT), which is currently under construction. The enormous ESO telescope with its 39-metre diameter primary mirror will be the world’s largest telescope for the visible and near-infrared range. Led by the Viennese astrophysicists, the Austrian team is involved in the development of the camera MICADO (Multi-AO Imaging Camera for Deep Observations), which will permit more precise imaging of near-infrared wavelengths. The Mid-Infrared ELT Imager and Spectrograph (METIS) will provide high-resolution data from the mid-infrared spectrum. The third instrument, MOSAIC, will allow spectroscopic analyses of very distant galaxies. One of the tasks of the Austrian team is to develop components for the data reduction software of the instruments.

Furthermore, the Institute operates astronomical observation stations in Vienna (including 0.8m reflector "vienna little telescope") and on the Mitterschöpfl (Leopold Figl Observatory for Astrophysics, including a 1.5m Ritchey Crétien telescope), which give a benefit to research-related education and public relations.

 New instruments can also be tested on these local telescopes. Also a small radio telescope for detecting the 21cm line of the neutral hydrogen are in use.