Mass-loss rates and dust-to-gas ratios for obscured Asymptotic Giant Branch stars of different metallicities

The mass-loss rates and dust-to-gas ratios of obscured Asymptotic Giant Branch (AGB) stars are investigated for samples with different initial metallicities: in the Small and Large Magellanic Clouds (SMC & LMC) and in the Milky Way. The properties of their circumstellar envelopes can be explained in a consistent way if, both for obscured M-type AGB stars and for obscured carbon stars, the total (gas+dust) mass-loss rate depends only weakly on initial metallicity whilst the dust-to-gas ratio depends approximately linearly on initial metallicity.