Research

Galaxies and Universe

Questions about the origin, the formation and evolution of galaxies and their components (gas, stars, black holes, dark matter), and the interactions between these components and the "cosmic space" (intergalactic space and large structures) are among the key themes of contemporary astrophysics. Given the nature and complexity of these phenomena, these issues require a global and diversified approach. In addition, the multi-wavelength observations are required to study different populations of galaxies to determine their various components, and to detect the most distant galaxies.

In this context, the group is working on the structure and evolution of galaxies and the associated problems of theoretical astrophysics. This group has obtained original and fundamental results going from the chaotic dynamics in spiral galaxies, the evolutionary link between bulbs and galactic bars, or the quantum effects that cosmological neutrinos induce on cosmological structures. The group is also studying an original hypothesis of baryonic dark matter involving hydrogen and helium at a temperature close to 3K. In this regard, in order to be able to study the very cold and almost invisible matter in galaxies, but at best with millimeter waves, the group developed an observational component using the current and next generation of millimeter and sub-millimeter interferometers especially the Atacama Large Millimeter Array (ALMA) in Chile. From 2012, ALMA will increase between 10 and 100 times the current performance in this field of observations. This core expertise in millimeter astronomy, new in Switzerland, is developed to provide support to other astronomers interesting to use the same techniques to other objects (deep Universe or formation of stars and planets).

The formation and evolution of stars and galaxies in the history of the Universe, and the study of the first galaxies in particular, are major themes of astrophysics. This booming research topic, appeals to observations made with the most powerful instruments on the ground, the Very Large Telescope (VLT) at ESO and in space (Hubble Space Telescope HST or SPITZER). In particular, these instruments have detected the most distant galaxies, seen as they were just 1 billion years after the Big Bang. These observations thus represent "back-in-time machines" tracing direct the formation of stars and galaxies on almost all of the history of the Universe.

The followed approaches include the theory, numerical simulations (hydrodynamics, N-Body, radiative transfer models spectra of galaxies etc.), observations, and the  interpretation thereof. To do this, groups develop and use numerical codes, make simulations, maintain clusters of parallel computing, and participate in numerous observations exploiting instruments and existing infrastructures.

Among the current issues where the efforts are concentrated include

  • When did the first galaxies form?
  • What are their properties and their contribution to reionization?
  • How to constrain the properties of dark matter baryonic or not?
  • Is there a significant population of galaxies obscured by dust at high redshift?
  • What is the relationship between different populations of galaxies?
  • How does change the content in gas, dust and stars in the galaxies?

To answer these questions ultra-deep and multi-wavelength observations (especially visible, NIR, IR and sub-mm) ground and space will be undertaken, in particular with the VLT, HST, SPITZER, HERSCHEL, IRAM and ALMA soon. Simulation and modeling tools of prime importance for the interpretation of these data will also be improved.

Studies undertaken in the field of Galaxies and Universe cover a wide field of the physics of galaxies, star formation, stellar populations and the interstellar space, with interesting implications for other areas, such as stellar physics and cosmology. Some of these issues thus benefit from interesing synergies  with other research groups in the Astronomy Department  of the University of Geneva, the Department of Physics (CAP) and the Laboratory of Astrophysics of the EPFL (LASTRO).

The topics studied in the Department fit perfectly in modern astrophysics major objectives, as identified in various "roadmaps" (eg Switzerland Roadmap of Astronomy and  the European strategic plan ASTRONET). These topics are also among the main justifications for the construction of new telescopes, observatories and satellites, such as ALMA, E-ELT and JWST.