SPECIAL SEMINAR: Why does a dark matter universe make MONDian galaxies?

The kinematics of galaxies are very tightly predicted by their gas and stellar mass alone -- this is a remarkable truth if galaxies are mostly dark matter. The Baryonic Tully-Fisher Relation (BTFR) and related Radial Acceleration Relation (RAR) both embody this connection, encoding a universal acceleration scale in galactic kinematics on the order g† = 10-8 cm s-2. This is a key prediction of MOdified Newtonian Dynamics (MOND), in which g† is a fundamental constant below which gravity is no longer Newtonian. However, many recent works simulating galaxy formation in ΛCDM have also reproduced the RAR and BTFR. I will propose a simple explanation for why this works: g† is encoded in the same stellar feedback mechanisms that are responsible for setting all other fundamental galaxy scaling relations involving baryonic matter: stellar radiation, stellar winds, and supernova explosions. I will highlight a recent body of work by several groups performing controlled, high-resolution, cosmologically-agnostic simulations of star-forming ISM patches. These works agree that feedback from a stellar population, taken in aggregate, imparts a specific momentum per unit stellar mass at a rate on the order of 10-8 cm s-2. It follows that g† demarcates the transition point in a galaxy between efficient star formation (where baryons will dominate) and inefficient star formation (where dark matter will dominate). This can explain the tight connection between galactic kinematics and baryon content in a dark matter cosmology, and the universal acceleration scale in galaxies.