LYRA I: Simulating the multi-phase ISM of a dwarf galaxy with variable
  energy supernovae from individual stars
  We introduce the LYRA project, a new high resolution galaxy formation model
built within the framework of the cosmological hydro-dynamical moving mesh code
AREPO. The model resolves the multi-phase interstellar medium down to 10 K. It
forms individual stars sampled from the initial mass function (IMF), and tracks
their lifetimes and death pathways individually. Single supernova (SN) blast
waves with variable energy are followed within the hydrodynamic calculation to
interact with the surrounding interstellar medium (ISM). In this paper, we
present the methods and apply the model to a $10^{10} M_{\odot}$ isolated halo.
We demonstrate that the majority of supernovae are Sedov-resolved at our
fiducial gas mass resolution of $4 M_{\odot}$. We show that our SN feedback
prescription self-consistently produces a hot phase within the ISM that drives
significant outflows, reduces the gas density and suppresses star formation.
Clustered SN play a major role in enhancing the effectiveness of feedback,
because the majority of explosions occur in low density material. Accounting
for variable SN energy allows the feedback to respond directly to stellar
evolution. We show that the ISM is sensitive to the spatially distributed
energy deposition. It strongly affects the outflow behaviour, reducing the mass
loading by a factor of 2-3, thus allowing the galaxy to retain a higher
fraction of mass and metals. LYRA makes it possible to use a comprehensive
multi-physics ISM model directly in cosmological (zoom) simulations of dwarf
and higher mass galaxies.
