The Effects of Cosmic Rays on the Chemistry of Dense Cores. (arXiv:2206.11167v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+ODonoghue_R/0/1/0/all/0/1">Ross O&#x27;Donoghue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Viti_S/0/1/0/all/0/1">Serena Viti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Padovani_M/0/1/0/all/0/1">Marco Padovani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+James_T/0/1/0/all/0/1">Tomas James</a>

Cosmic rays are crucial for the chemistry of molecular clouds and their
evolution. They provide essential ionizations, dissociations, heating and
energy to the cold, dense cores. As cosmic rays pierce through the clouds they
are attenuated and lose energy, which leads to a dependency on the column
density of a system. The detailed effects these particles have on the central
regions still needs to be fully understood. Here, we revisit how cosmic rays
are treated in the UCLCHEM chemical modeling code by including both ionization
rate and H2 dissociation rate dependencies alongside the production of cosmic
ray induced excited species and we study in detail the effects of these
treatments on the chemistry of pre-stellar cores. We find that these treatments
can have significant effects on chemical abundances, up to several orders of
magnitude, depending on physical conditions. The ionization dependency is the
most significant treatment, influencing chemical abundances through increased
presence of ionized species, grain desorptions and enhanced chemical reactions.
Comparisons to chemical abundances derived from observations show the new
treatments reproduce these observations better than the standard handling. It
is clear that more advanced treatments of cosmic rays are essential to chemical
models and that including this type of dependency provides more accurate
chemical representations.

Cosmic rays are crucial for the chemistry of molecular clouds and their
evolution. They provide essential ionizations, dissociations, heating and
energy to the cold, dense cores. As cosmic rays pierce through the clouds they
are attenuated and lose energy, which leads to a dependency on the column
density of a system. The detailed effects these particles have on the central
regions still needs to be fully understood. Here, we revisit how cosmic rays
are treated in the UCLCHEM chemical modeling code by including both ionization
rate and H2 dissociation rate dependencies alongside the production of cosmic
ray induced excited species and we study in detail the effects of these
treatments on the chemistry of pre-stellar cores. We find that these treatments
can have significant effects on chemical abundances, up to several orders of
magnitude, depending on physical conditions. The ionization dependency is the
most significant treatment, influencing chemical abundances through increased
presence of ionized species, grain desorptions and enhanced chemical reactions.
Comparisons to chemical abundances derived from observations show the new
treatments reproduce these observations better than the standard handling. It
is clear that more advanced treatments of cosmic rays are essential to chemical
models and that including this type of dependency provides more accurate
chemical representations.

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