Benoit Famaey (CNRS/University of Strasbourg)
Galaxy dynamics is confronted with one of the deepest problems of modern physics: the dark matter problem. The motions of stars and gas observed exceed what can be explained by the mass visible in those same stars and gas. Either (i) there is a vast amount of unseen mass in some novel form – dark matter – or (ii) the data indicate a breakdown of our understanding of dynamics on the relevant scales, or (iii) both. We shall review the observational evidence for an intimate connection between the baryonic surface density and the total gravitational field in galaxies. This observational fact presents a fine-tuning problem for the particle dark matter interpretation of mass discrepancies in galaxies. On the other hand, this is naturally explained within the MOND paradigm, hypothesizing an effective breakdown of Newtonian dynamics in the extremely low acceleration regime. However, MOND predictions break down on scales larger than galaxies. Theories proposing a Lagrangian of the “dark sector” accounting for the MOND phenomenology in galaxies while preserving the predictions of the current standard cosmological model on the largest scales are perhaps a promising way to reconcile these conflicting observational facts.
Benoit Famaey, PhD, is a Senior Research Associate of the CNRS at the University of Strasbourg (France). He received Bachelor’s, Master’s and PhD degrees from Brussels University (Belgium). He then went on a postdoc at the Rudolf Peierls Centre for Theoretical Physics in Oxford (UK), before going back to Brussels for another postdoc, and to the Argelander Institute for Astronomy in Bonn (Germany) as a Humboldt Fellow. He is serving as a CNRS Senior Research Associate at the University of Strasbourg since 2009. He is investigating the dynamics of stars in our own Galaxy, the Milky Way, as well as external galaxies, and the implications for the dark matter problem. He was awarded in recent years the “Prix Espoir de l’Université de Strasbourg 2015”, and the “Prix Sciences 2018 de l’Académie Rhénane”.