The formation of exponential disk galaxies in MOND
  The formation and evolution of galaxies is highly dependent on the dynamics
of stars and gas, which is governed by the underlying law of gravity. To
investigate how the formation and evolution of galaxies takes place in
Milgromian gravity (MOND), we present full hydrodynamical simulations with the
Phantom of Ramses (POR) code. These are the first-ever galaxy formation
simulations done in MOND with detailed hydrodynamics, including star formation,
stellar feedback, radiative transfer and supernovae. These models start from
simplified initial conditions, in the form of isolated, rotating gas spheres in
the early Universe. These collapse and form late-type galaxies obeying several
scaling relations, which was not a priori expected. The formed galaxies have a
compact bulge and a disk with exponentially decreasing surface mass density
profiles and scale lengths consistent with observed galaxies, and vertical
stellar mass distributions with distinct exponential profiles (thin and thick
disk). This work thus shows for the first time that disk galaxies with
exponential profiles in both gas and stars are a generic outcome of collapsing
gas clouds in MOND. These models have a slight lack of stellar angular momentum
because of their somewhat compact stellar bulge, which is connected to the
simple initial conditions and the negligible later gas accretion. We also
analyse how the addition of more complex baryonic physics changes the main
resulting properties of the models and find this to be negligibly so in the
Milgromian framework.
