Cosmic evolution of dust in galaxies: Methods and preliminary results

Abstract

We investigate the redshift (z) evolution of dust properties, its dependences on initial conditions of galaxy formation, and physical correlations between dust, gas, and stellar contents at different z based on our original chemodynamical simulations of galaxy formation with dust growth and destruction. In this preliminary investigation, we first determine the reasonable ranges of the most important two parameters for dust evolution, i.e., the timescales of dust growth and destruction, by comparing the observed and simulated dust properties and molecular hydrogen H2 content of the Galaxy. We then investigate the z-evolution of dust-to-gas-ratios (D) and, H2 gas fraction (f_H2), and gas-phase chemical abundances (e.g., A_O=12+log(O/H)) in the simulated disk and dwarf galaxies. The principal results are as follows. Both D and f_H2 can rapidly increase during the early dissipative formation of galactic disks (z ~ 2-3) and the z-evolution of these depends on initial mass densities, spin parameters, and masses of galaxies. The observed A_O-D relation can be qualitatively reproduced, but the simulated dispersion of D at a given A_O is smaller. The simulated galaxies with larger total dust masses show larger H2 and stellar masses and higher f_H2. Disk galaxies show negative radial gradients of D and the gradients are steeper for more massive galaxies. Both dust-to-metal ratios and gas-phase [S/Fe] can be significantly different within a single galaxy and between different galaxies at different z, which means that fixed dust-to-metal ratios should not be used in investigating H2 contents and spectral energy distributions of galaxies.