2025MNRAS.543.2997B

Recent observations have revealed significant variations in the abundances of gas- and ice-phase molecules in galaxies with different luminosities and types. In order to discuss the physical origins of these variations, we incorporate gas- and dust-phase interstellar chemistry into galaxy-scale simulations with various baryonic physics including dust formation, evolution, and destruction, all of which are essential for the calculations of $\approx 400$ interstellar molecule species. The new simulations can accordingly predict the abundances of gas- and ice-phase molecular species such as ${\rm H_2O}$ and ${\rm CO_2}$ ice within individual molecular gas cloud of galaxies based on gas density and temperature, dust temperature ($T_{\rm dust}$), elemental abundances (e.g. CHNOPS), UV radiation strength ($F_{\rm UV}$), and cosmic ray ionization rate ($\zeta _{\rm CR}$) within the clouds. Since this is the first of the series of papers, we describe the details of the new simulations and present the preliminary results focused on the spatial distributions of ${\rm H_2O}$, CO, ${\rm CO_2}$, and ${\rm CH_3OH}$ ice species in a disc galaxy similar to the Milky Way. We particularly discuss how $T_{\rm dust}$ and gas-phase elemental abundances can control the spatial distributions of the above molecules in galaxies. We briefly discuss the total amount of ${\rm H_2O}$ and ${\rm CO_2}$ ices and radial distributions of PN and PO molecules in the Galaxy.