Synthetic Observations of Carbon Lines of Turbulent Flows in the Diffuse Multiphase Interstellar Medium

We examine observational characteristics of multi-phase turbulent flows inthe diffuse interstellar medium (ISM) using a synthetic radiation field ofatomic and molecular lines. We consider the multi-phase ISM which is formed bythermal instability under the irradiation of UV photons with moderate visualextinction $A_V\sim 1$. Radiation field maps of C$^{+}$, C$^0$, and CO lineemissions were generated by calculating the non-local thermodynamic equilibrium(nonLTE) level populations from the results of high resolution hydrodynamicsimulations of diffuse ISM models. By analyzing synthetic radiation field ofcarbon lines of [\ion{C}{2}] 158 $\mu$m, [\ion{C}{1}] $^3P_2-^3P_1$ (809 GHz),$^3P_1-^3P_0$ (492 GHz), and CO rotational transitions, we found a high ratiobetween the lines of high- and low-excitation energies in the diffusemulti-phase interstellar medium. This shows that simultaneous observations ofthe lines of warm- and cold-gas tracers will be useful in examining the thermalstructure, and hence the origin of diffuse interstellar clouds.