Le 27 septembre 2019
De 10h30 à 12h00
Justin Read
University of Surrey
Dark matter makes up most of the mass of the Universe but remains mysterious. I discuss recent progress in constraining its properties by measuring its distribution in the Universe from tiny dwarf galaxies to giant galaxy clusters. I show that the latest results favour a cold, collisionless particle that lies beyond the standard model of particle physics. However, for a long time this model has been in tension with the abundance and internal dark matter distribution of nearby dwarf galaxies, tensions that have become known as the « cusp-core », « missing satellites » and « too big to fail » problems. I present the first observational evidence that the cusp-core problem owes to baryonic feedback « heating up » dark matter during galaxy formation, and I show that this naturally solves both the missing satellites and « too big to fail » problems too. This provides further evidence that dark matter is, to a good approximation, a cold, collisionless fluid that can be heated up and moved around. I conclude with a discussion of the latest constraints on self-interacting and warm dark matter models.