Synthetic observations of molecular clouds in a galactic center
  environment: I. Studying maps of column density and integrated intensity
  We run numerical simulations of molecular clouds (MCs), adopting properties
similar to those found in the Central Molecular Zone (CMZ) of the Milky Way.
For this, we employ the moving mesh code Arepo and perform simulations which
account for a simplified treatment of time-dependent chemistry and the
non-isothermal nature of gas and dust. We perform simulations using an initial
density of n_0 = 10^3 cm^{-3} and a mass of 1.3x10^5 M_sun. Furthermore, we
vary the virial parameter, defined as the ratio of kinetic and potential
energy, alpha = E_{kin} / |E_{pot}|, by adjusting the velocity dispersion. We
set it to alpha = 0.5, 2.0 and 8.0, in order to analyze the impact of the
kinetic energy on our results. We account for the extreme conditions in the CMZ
and increase both the interstellar radiation field (ISRF) and the cosmic-ray
flux (CRF) by a factor of 1000 compared to the values found in the solar
neighbourhood. We use the radiative transfer code RADMC-3D to compute synthetic
images in various diagnostic lines. These are [CII] at 158 micron, [OI] (145
micron), [OI] (63 micron), 12CO (J = 1 -> 0) and 13CO (J = 1 -> 0) at 2600
micron and 2720 micron, respectively. When alpha is large, the turbulence
disperses much of the gas in the cloud, reducing its mean density and allowing
the ISRF to penetrate more deeply into the cloud's interior. This significantly
alters the chemical composition of the cloud, leading to the dissociation of a
significant amount of the molecular gas. On the other hand, when alpha is
small, the cloud remains compact, allowing more of the molecular gas to
survive. We show that in each case the atomic tracers accurately reflect most
of the physical properties of both the H2 and the total gas of the cloud and
that they provide a useful alternative to molecular lines when studying the ISM
in the CMZ.
