After being launched last summer, ESA's Euclid space telescope has already been delivering data for almost a year. The first scientific results are being published today. They show that the new instrument is capable of detecting a representative sample of all galaxies in the universe. For example, a study led by the University of Innsbruck was able to identify over 600 previously unknown dwarf galaxies in the Perseus galaxy cluster.
The study, led by Francine Marleau from the Department of Astro- and Particle Physics at the University of Innsbruck, has identified a total of 1100 dwarf galaxies in the Perseus galaxy cluster, more than 630 of which were previously undiscovered. Dwarf galaxies are very difficult to find because they are not very bright and their light is diffuse across the sky. The team led by Francine Marleau analysed the structure and size of the dwarf galaxies based on data from the Euclid space telescope and also found clusters of stars around the galaxies. With the help of the discovered galaxies, the team was also able to determine the so-called luminosity function. "This function can be understood as the result of a census," explains Francine Marleau. "It indicates how many galaxies there are with a certain luminosity. With the newly discovered dwarf galaxies, we were able to extend our knowledge of this function to much 'dimmer' galaxies."
In addition to the Perseus galaxy cluster, the nine scientific papers now published also examined the Fornax galaxy cluster, where 5,000 new star clusters were found. "Galaxies were also discovered in our 'nearer' neighbourhood," explains Laila Linke, postdoctoral researcher at the Institute of Astro- and Particle Physics and project leader. "In astronomical terms, however, close still means 1.6 million light years to 29.7 million light years away from Earth." There, the telescope can take images of individual stars and the scientists can use them to characterise different stellar populations.
On the trail of dark matter
Galaxy clusters contain a lot of dark matter. Their mass distorts the observed shapes of distant background galaxies due to gravitational lensing. Research group leader Tim Schrabback, also at the Institute of Astro- and Particle Physics, analysed the dark matter of the galaxy cluster Abell 2390 with an international team. "Our study shows how excellently suited the new instrument is for this analysis," says a delighted Tim Schrabback. "By observing the distortion of the shapes of background galaxies, we were able to measure the distribution of dark matter in and around the galaxy cluster."
The new results demonstrate the strengths of the Euclid telescope: "The new instrument can observe a large area of the night sky at once and thus provides a representative sample of all galaxies," says Laila Linke. "Thanks to the high sensitivity to surface brightness, we can also find dwarf galaxies and very diffuse galaxies. With the particularly sharp images thanks to the high spatial resolution, we can identify dwarf galaxies and at the same time discover and characterise so-called nuclear star clusters and globular clusters."
New instrument for science
TheEuropean Space Agency's (ESA) Euclid space telescope was launched just under a year ago, on 1 July 2023, and is set to create the largest 3D map of the universe to date. Scientists hope to learn more about the previously unexplored dark matter and dark energy that make up the Universe. The data from Euclid will be analysed by the international Euclid consortium. Over the next few years, the 1.2 metre diameter space telescope will create the largest and most accurate 3D map of the Universe and observe billions of galaxies. Euclid can use this map to reveal how the universe expanded after the Big Bang and how the structures in the Universe have developed. This will give scientists more clues to better understand the role of gravity and the nature of dark energy and dark matter. Over 1,000 scientists from around 200 institutes and laboratories are jointly analysing the mission data, which will also be supplemented by ground-based telescopes. The research teams of Tim Schrabback and Francine Marleau at the University of Innsbruck are significantly involved in the project.
