H2 chemistry in galaxy simulations: an improved supernova feedback model
  In this study, we present and validate a variation of recently-developed
physically motivated sub-grid prescriptions for supernova feedback that account
for the unresolved energy-conserving phase of the bubble expansion. Our model
builds upon the implementation publicly available in the mesh-less hydrodynamic
code GIZMO, and is coupled with the chemistry library KROME. Here, we test it
against different setups, to address how it affects the formation/dissociation
of molecular hydrogen (H$_2$). First, we explore very idealised conditions, to
show that it can accurately reproduce the terminal momentum of the blast-wave
independent of resolution. Then, we apply it to a suite of numerical
simulations of an isolated Milky Way-like galaxy and compare it with a similar
run employing the delayed-cooling sub-grid prescription. We find that the
delayed-cooling model, by pressurising ad-hoc the gas, is more effective in
suppressing star formation. However, to get this effect, it must maintain the
gas warm/hot at densities where it is expected to cool efficiently,
artificially changing the thermo-chemical state of the gas, and reducing the
H$_2$ abundance even in dense gas. Mechanical feedback, on the other hand, is
able to reproduce the H$_2$ column densities without altering the gas
thermodynamics, and, at the same time, drives more powerful outflows. However,
being less effective in suppressing star formation, it over-predicts the
Kennicutt-Schmidt relation by a factor of about 2.5. Finally, we show that the
model is consistent at different resolution levels, with only mild differences.
