Probing dust production in the Local Group

Observations of AGB stars in the Magellanic Clouds with the Infrared Spectrograph on the Spitzer Space Telescope have revealed that the rate of dust production by oxygen-rich stars decreases in more metal-poor environments, while the production of dust by carbon stars shows no detectable dependence on metallicity. Observations in other Local Group galaxies extend the lack of a dependence for carbon stars to lower metallicities. Studies of low-mass oxygen-rich AGB stars in Galactic globular clusters reinforce the metallicity dependence detected in the Magellanic Clouds. Because the AGB dominates dust input into the interstellar medium, it follows that in more metal-poor galaxies, interstellar dust will be more carbon rich.