Starting signal for the exploration of the invisible universe

With the rocket launch on July 1 at 11:12 local time in Florida (17:12 CET), the Euclid mission of the European Space Agency ESA will begin to explore the dark matter and dark energy of the universe. The research teams of Tim Schrabback and Francine Marleau at the University of Innsbruck are also significantly involved in the project and are busy preparing for the mission and evaluating the results.

The 1.2-meter-diameter space telescope is expected to produce the largest and most accurate 3D map of the universe over the next several years, observing billions of galaxies up to 10 billion light-years away. From this map, Euclid can reveal how the universe expanded after the Big Bang and how the structures in the universe evolved. This will give scientists more clues to better understand the role of gravity and the nature of dark energy and dark matter.

What are dark matter and dark energy?

The light sources of the universe - planets, stars, galaxies and gases - have been studied for centuries. 95% of the universe, however, consists of unknown and invisible quantities that influence the distribution and motion of objects in the universe. These are called dark energy and dark matter by scientists. However, nobody knows what exactly these quantities are. Understanding dark energy and dark matter is one of the greatest challenges in physics today.

Important participation of the University of Innsbruck

The research area of Tim Schrabback's group is extragalactic astrophysics and cosmology. Francine Marleau and her group are investigating the formation and evolution of galaxies. Together, the teams are intensively involved in the preparation of the Euclid mission and will also take on important tasks in the evaluation of the measurements. In the process, they are dealing with many different tasks:

Image calibration: All matter, including dark matter, distorts the images of galaxies as if through a magnifying glass. This is called the gravitational lensing effect. To determine the degree of distortion, the shapes of the observed galaxies must be determined. Since these galaxies are often only a few pixels in size and sometimes very faint, it is not so easy to measure shapes accurately. The methods used for this purpose must be calibrated on highly realistic image simulations. This is the main topic of two FFG/BMK-funded projects at the University of Innsbruck: "For example, we are optimizing methods for the realistic display of galaxy images and are also testing the use of AI-supported algorithms for this purpose," explains PhD student Benjamin Csizi. "Likewise, we are investigating methods that reduce the enormous computing power and thus energy requirements of such simulations," adds Henning Jansen, also a doctoral student in Tim Schrabback's research group.

Cosmology with the gravitational lensing effect: From the measured galaxy image distortions, cosmological parameters can be determined that describe the expansion and evolution of the universe, in particular the amount of dark matter as well as the dynamics of dark energy. However, to get from observed galaxies to these parameters, whole catalogs of galaxies have to be statistically evaluated and compared to models. These statistical methods are being co-developed in Innsbruck in a new FWF/ESPRIT project led by postdoctoral researcher Laila Linke and tested by realistic simulations.

Cosmology with galaxy clusters: Cosmological parameters can also be determined with the help of galaxy clusters. These are structures of hundreds to thousands of galaxies, with about 10¹⁴ solar masses. "The number of these galaxy clusters per mass determines how complex structures have formed in the universe. Using Euclid and the gravitational lensing effect, we can estimate the mass of the clusters and compare them to cosmological model predictions," explains Sebastian Grandis, Senior Scientist at the Institute of Astro- and Particle Physics at the University of Innsbruck.

Galaxy formation in the "local universe": Euclid's sensitivity, spatial resolution, and wavelength coverage make it an ideal facility to study the properties of galaxies in detail. Francine Marleau's group is focusing in particular on dwarf galaxies and galaxies with low surface brightness. These dwarf galaxies are particularly interesting because their formation and evolution are not yet well described. They can also be used to study questions about the formation of the first generation of stars, the growth of black holes, and the properties of dark matter.

Quotes

"Dark matter and dark energy make up 95% of the energy and matter content of the universe - and yet we don't know what they are. Dark energy in particular is fascinating because it determines how the universe will expand and what its "fate" will be. With Euclid, we will be able to determine with unprecedented precision how dark energy behaves and thus predict the future of our Universe." (Laila Linke, postdoctoral researcher at the Institute for Astro- and Particle Physics and project leader)

"In the past, the famous Hubble Space Telescope revolutionized astronomy and astrophysics with its sharp images that are not washed out by the air turbulence of the Earth's atmosphere. What's new about Euclid is its 180 times larger field of view compared to Hubble. This allows Euclid to obtain similarly sharp images for a large portion of the sky for the first time. These data will be invaluable to a wide range of research fields within astronomy and astrophysics." (Francine Marleau, associate professor at the Institute for Astro- and Particle Physics and research group leader)

"The gravitational lensing effect is the only method that allows us to directly map the mass distribution in the universe. In this context, Euclid's data set will outperform all previous programs by at least a factor of 10. This opens up tremendous opportunities to better understand the mysteries of the cosmos. At the same time, however, it challenges us to refine our analysis techniques in such a way that they can keep up with the demands of this increased accuracy. In this context, we are pleased to be able to make significant contributions to the success of the Euclid mission from Innsbruck." (Tim Schrabback, professor at the Institute for Astro- and Particle Physics and working group leader ).

Further Information

Detailed information about the mission can be found in the official launch kit of ESA
https://www.esa.int/ESA_Multimedia/Images/2023/05/Euclid_launch_kit_cover

Official press release (only available in German):

https://presse.uibk.ac.at/news-startschuss-fuer-die-erforschung-des-unsichtbaren-universums?id=181532&menueid=24035&l=deutsch

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