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

Abstract

We examine observational characteristics of multi-phase turbulent flows in the diffuse interstellar medium (ISM) using a synthetic radiation field of atomic and molecular lines. We consider the multi-phase ISM which is formed by thermal instability under the irradiation of UV photons with moderate visual extinction $A_V\sim 1$. Radiation field maps of C${}^{+}$, C${}^0$, and CO line emissions were generated by calculating the non-local thermodynamic equilibrium (nonLTE) level populations from the results of high resolution hydrodynamic simulations of diffuse ISM models. By analyzing synthetic radiation field of carbon lines of [\ion{C}{2}] 158 $\mu$m, [\ion{C}{1}] ${}^3{P}_2{-}^3{P}_1$ (809 GHz), ${}^3{P}_1{-}^3{P}_0$ (492 GHz), and CO rotational transitions, we found a high ratio between the lines of high- and low-excitation energies in the diffuse multi-phase interstellar medium. This shows that simultaneous observations of the lines of warm- and cold-gas tracers will be useful in examining the thermal structure, and hence the origin of diffuse interstellar clouds.

arXiv comment16 pages, 10 figures : accepted for publication in ApJ. PDF version with high resolution figures is available (http://yso.mtk.nao.ac.jp/~ymasako/paper/ms_hires.pdf)

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