Misc,
Simulating the H2 content of high-redshift galaxies
(2014)cite arxiv:1403.7132Comment: 16 pages, 12 figures. Submitted to MNRAS. Comments welcome.
Abstract
We introduce a sub-grid model for the non-equilibrium abundance of molecular
hydrogen in cosmological simulations of galaxy formation. We improve upon
previous work by accounting for the unresolved structure of molecular clouds in
a phenomenological way which combines both observational and numerical results
on the properties of the turbulent interstellar medium. We apply the model to a
cosmological simulation of the formation of a Milky-Way-sized galaxy at z=2,
and compare the results to those obtained using other popular prescriptions
that compute the equilibrium abundance of H2. In these runs we introduce an
explicit link between star formation and the local H2 abundance, and perform an
additional simulation in which star formation is linked directly to the density
of cold gas. We find that, although the global properties of the simulated
galaxy are relatively insensitive to the sub-grid H2 models, the resulting
spatial distribution of H2 is not: molecules extend further into the outer disc
of the galaxy in our non-equilibrium model. In addition, the destruction of
molecules by supernovae, if substantial, may result in a depletion of the H2
abundance in the innermost 2-3 kpc. Finally, we study dwarf-sized galaxies that
lie in the high-resolution region of our simulations and show that their star
formation histories are significantly affected by both early metal enrichment
and numerical resolution. We conclude that further work is needed in order to
verify recent claims on the abundance of dark galaxies at high redshift.
