EXTRADARK · Extragalactic stellar streams as astrophysical tools to decipher dark matter

Extragalactic stellar streams as astrophysical tools to decipher dark matter

Dark matter constitutes over 80% of the universe's matter, yet its true nature remains a mystery. Understanding dark matter is essential because it significantly influences the formation and structure of the universe. It affects how galaxies form and behave and offers insights into the fundamental laws of physics. It's called "dark" because it doesn’t emit, absorb, or reflect light, making it invisible and difficult to detect. However, we know it exists due to its gravitational effects on visible objects like stars and galaxies. Dark matter forms large halos around galaxies, with many smaller clumps called subhalos. The characteristics of these subhalos depend on the properties of dark matter particles. If dark matter is made of light particles, it moves quickly in the early universe and forms fewer clumps. Conversely, if it's composed of massive particles, it moves slower and clumps together more easily. Since dark matter doesn’t interact with light, we can’t see it directly. Instead, we study its effects on visible matter, such as stars. In this project, I will investigate stellar streams, which are long, thin groups of stars pulled out of star clusters or small galaxies by the gravitational forces of a larger galaxy. Imagine a string of pearls stretched into a line. These stellar streams help us study the invisible dark matter surrounding galaxies, as the way the stars are pulled and stretched reveals important information about the dark matter's presence and distribution. New telescopes like the Vera C. Rubin Observatory, Euclid, and NASA's Nancy Grace Roman Telescope will soon discover many more streams in galaxies beyond our own. My project aims to fill the gaps in our current knowledge so we can make sense of this new data and extract the most information about dark matter from stellar streams. We don't know how many streams exist in the outer regions of galaxies or their exact locations. This information is crucial for comparing theoretical models with actual data. In this project, I'll predict the number and location of streams in various galaxies, helping future observations focus on the right areas. By predicting where thin streams from globular clusters are in external galaxies using theoretical models and simulations, I will provide a foundation for understanding the number of streams per galaxy. Additionally, we need to understand how to use streams in other galaxies to learn about dark matter. I'll study how multiple streams can provide better constraints on dark matter properties than individual streams. This involves creating methods to analyze stream data and predict dark matter distributions. Using simulations and theories, I'll develop tools and methods that can be used by the wider scientific community to understand how streams in different types of galaxies can reveal dark matter properties. Finally, to make meaningful comparisons, we need data from many galaxies, especially dwarf galaxies. I'll develop models to predict how streams form and evolve in dwarf galaxies, considering different dark matter scenarios. This will prepare us to interpret new data from upcoming observations and understand how they fit with existing dark matter theories. By creating these models, I'll help us anticipate what to expect from future observations and how they align with current dark matter paradigms. By addressing these gaps, my research will advance our understanding of dark matter and enhance our ability to interpret new astronomical data.

Data: CORDIS, © European Union