Fredagskollokvium: Galactic dynamics and the nature of dark matter 

Benoit Famaey, Observatoire Astronomique de Strasbourg

In this talk, I will review the observational evidence for an intimate connection between the baryonic surface density and the total gravitational field in disk galaxies. This observational fact presents a fine-tuning problem for the particle dark matter interpretation of mass discrepancies in galaxies. I particular, it leads to a too high "diversity" of rotation curve shapes for a given mass. On the other hand, this phenomenology is naturally explained in a paradigm hypothesizing an effective breakdown of Newtonian dynamics in the extremely low acceleration regime (MOND). However, MOND predictions break down on scales larger than galaxies. Theories modifying the lagrangian of the dark matter sector to account for the observed phenomenology in galaxies while preserving the predictions of the standard cosmological model on the largest scales are perhaps a promising way to reconcile these conflicting observational facts. I will present some tentative dark matter models which seem to fit the bill, as well as their current shortcomings. 


The measured circular velocity at 2 kpc from the center of disk galaxies in the nearby Universe (within ~100 Mpc) is plotted as a function of the maximum circular velocity of their dark matter halo. The scatter is indicative of a large diversity of galaxy rotation curve shapes at a given halo mass scale, which is difficult to reproduce in current simulations of galaxy formation. Credits: Ghari, Famaey, Laporte & Haghi, Astronomy & Astrophysics, in press, eprint arXiv:1811.06554


Publisert 5. des. 2018 14:41 - Sist endret 13. mars 2019 22:21