Fellows Seminar - How to observe the invisible: the quest for dark matter around galaxies

By Florent Renaud, 2023 Fellow

For several decades now, independent observations of the nearby Universe seem contradictory: galaxies are spinning too fast. At the measured rotation speeds, the centrifugal force should break them up. Unless… we are underestimating their masses, and thus the gravity holding them together. If that is the case, then galaxies should also include a massive but invisible component, called dark matter, which would reconcile the observations.

However, the exact nature of dark matter is still a mystery. The most powerful particle accelerators have still not managed to detect it, and its invisible character makes it impossible to probe directly. One solution to better constrain the properties of dark matter is to evaluate its effects on luminous matter in the galactic outskirts. It is there that satellite galaxies dissolve when they fall onto a main galaxy, leaving behind a stream of their stars. By studying the properties of these streams, we can reconstruct the interaction between the satellites and the dark matter halo, and apply astrophysical constraints to the problem.

In this talk, after a broad introduction of the field, I will show the latest progress made at the Strasbourg astronomical observatory during my USIAS project to numerically model stellar streams, and to contribute to the quest for the mysterious dark matter.

• Read more about Florent Renaud and his USIAS project: Decoding dark matter using the Milky Way's stellar streams.