Modeling The Molecular Composition in an AGN Disk
  We use a high-temperature chemical network to derive the molecular abundances
in axisymmetric accretion disk models around active galactic nuclei (AGNs)
within 100 pc using simple radial and vertical density and temperature
distributions motivated by more detailed physical models. We explore the
effects of X-ray irradiation and cosmic ray ionization on the spatial
distribution of the molecular abundances of CO, CN, CS, HCN, HCO+, HC3N, C2H,
and c-C3H2 using a variety of plausible disk structures. These simple models
have molecular regions with a layer of X-ray dominated regions, a midplane
without the strong influence of X-rays, and a high-temperature region in the
inner portion with moderate X-ray flux where families of polyynes (C$_{\rm
n}$H$_{2}$) and cyanopolyynes can be enhanced. For the high midplane density
disks we explore, we find that cosmic rays produced by supernovae do not
significantly affect the regions unless the star formation efficiency
significantly exceeds that of the Milky Way. We highlight molecular abundance
observations and ratios that may distinguish among theoretical models of the
density distribution in AGN disks. Finally, we assess the importance of the
shock crossing time and the accretion time relative to the formation time for
various chemical species. Vertical column densities are tabulated for a number
of molecular species at both the characteristic shock crossing time and steady
state. Although we do not attempt to fit any particular system or set of
observations, we discuss our models and results in the context of the nearby
AGN NGC 1068.
