摘要: We present a new methodology for simulating mid-infrared emission from
polycyclic aromatic hydrocarbons (PAHs) in galaxy evolution simulations. To do
this, we combine theoretical models of PAH emission features as they respond to
varying interstellar radiation fields, grain size distributions, and ionization
states with a new on-the-fly model for dust evolution in hydrodynamic galaxy
simulations. We apply these models to 3 idealized arepo galaxy evolution
simulations within the smuggle physics framework. We use these simulations to
develop numerical experiments investigating the buildup of PAH masses and
luminosities in galaxies in idealized analogs of the Milky Way, a dwarf galaxy,
and starburst disk. Our main results follow. Galaxies with high specific star
formation rates have increased feedback energy per unit mass, and are able to
efficiently shatter dust grains, driving up the fraction of ultra small grains.
At the same time, in our model large radiation fields per unit gas density
convert aliphatic grains into aromatics. The fraction of dust grains in the
form of PAHs (q_PAH) can be understood as a consequence of these processes, and
in our model PAHs form primarily from interstellar processing (shattering) of
larger grains rather than from the growth of smaller grains. We find that the
hardness of the radiation field plays a larger role than variations in the
grain size distribution in setting the total integrated PAH luminosities,
though cosmological simulations are necessary to fully investigate the complex
interplay of processes that drive PAH band luminosities in galaxies. Finally,
we highlight feature PAH strength variations, cautioning against the usage of
emission templates with constant feature strength ratios.
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