IA/U.Lisboa Seminar - Tight galaxy scaling relations: dark matter vs. modified gravity - 16 maio 2017

In this talk, we 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. We show that this is the case even when taking baryonic feedback into account. 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 clearly breaks down on scales larger than galaxies, where there is ample evidence for a new degree of freedom behaving as a collisionless fluid of particles, i.e. dark matter.

 

Theories modifying the lagrangian of the dark matter sector to account for the baryon-dark matter connection in galaxies while preserving the predictions of LambdaCDM on the largest scales might perhaps be a promising way to reconcile these conflicting observational facts.