Coevolution of dust, gas and stars in galaxies - I. Spatial distributions and scaling-relations of dust and molecular hydrogen

We investigate the time evolution of dust properties, molecular hydrogen (H2) contents and star formation histories in galaxies by using our original chemodynamical simulations. The simulations include the formation of dust in the stellar winds of supernovae and asymptotic giant branch (AGB) stars, the growth and destruction processes of dust in the interstellar medium (ISM), the formation of polycyclic aromatic hydrocarbon (PAH) dust in carbon-rich AGB stars, the H-2 formation on dust grains and the H-2 photodissociation due to far-ultraviolet light in a self-consistent manner. We focus mainly on disc galaxies with the total masses ranging from 10(10) to 10(12) M-circle dot in this preliminary study. The principal results are as follows. The star formation histories of disc galaxies can be regulated by the time evolution of interstellar dust, mainly because the formation rates of H-2 can be controlled by dust properties. The observed correlation between dust-to-gas-ratios (D) and gas-phase oxygen abundances [A(O) equivalent to 12 + log (O/H)] can be reproduced reasonably well in the present models. The discs show negative radial gradients (i.e. larger in inner regions) of H-2 fraction (f(H)), PAH-to-dust mass ratio (f(PAH)), D and A(O), and these gradients evolve with time. The surface mass densities of dust (Sigma(dust)) are correlated more strongly with the total surface gas densities (Sigma(gas)) than with those of H-2 (Sigma(H2)). Local gaseous regions with higher D are more likely to have higher f(H) in individual discs and total H-2 masses (M-H2) correlate well with total dust masses (M-dust). More massive disc galaxies are more likely to have higher D, f(PAH) and f(H2), and smaller dust-to-stellar mass ratios (R-dust = M-dust/M-star). Early-type E/S0 galaxies formed by major galaxy merging can have lower R-dust than isolated late-type disc galaxies. We also compare between galactic star formation histories in the metallicity-dependent and dust-dependent star formation models and find no major differences. Based on these results, we discuss the roles of dust in chemical and dynamical evolution of galaxies.