| Abstract : | The Galactic Interstellar Medium is described by its distinct phases that span a variety of physical and chemical conditions. The typical physical conditions are studied using the spectral synthesis code CLOUDY. By setting up a grid of numerical models to simulate a wide array of conditions in the diffuse molecular ISM, the abundances of various chemical species are predicted. The models were based on inputs parameters such radiation fields, hydrogen densities, metallicity, cosmic ray ionization rates, etc. The predicted column densities of neutral hydrogen and H2 along with certain cloud properties like total hydrogen density, molecular fraction and rotational excitation temperatures are compared to those reported by Shull et al. (2021). Similarly, the column densities of metal species are compared to those reported by Konstantopoulou et al. (2022) for various Galactic sight-lines. The models predict diffuse gas with gas pressure falling between 457 to 9872 K cm−3, seen to be consistent with the observed values in the diffuse ISM. Similarly, the models also determine gas temperatures from 20 to 125 K and hydrogen densities ranging between 17 to 200 cm−3 which are optimal with the observed values in diffuse atomic and molecular clouds. Local interstellar radiation field within 0.5 𝐺0 and 5𝐺0 along with cosmic ray ionisation rate varying between -15.7 upto -15 (in log-scale units) applicable for diffuse molecular clouds in the Galactic ISM were also found. |
