Department of Astronomy Colloquium Series Presents:

The Life Cycle of Dust in the Magellanic Clouds: Insights from Spitzer and Herschel

The life cycle of dust in a galaxy involves the exchange of material between the interstellar medium (ISM) and stars. Dust is formed in the winds of dying stars, such as asymptotic giant branch (AGB) and red supergiant (RSG) stars, and the explosion of supernovae. In the ISM, the dust may be shattered and vaporized by supernova blast waves or accreted onto seed grains in the denser ISM. Dust is consumed in the star formation process and appears in the circumstellar environments of newly forming stars. By tracing the lifecycle of dust, we gain insights into the dust evolution processes and the origin of galactic dust. The Spitzer Space Telescope and Herschel Space Observatory provide a sensitive probe of circumstellar and interstellar dust. The Spitzer Surveying the Agents of Galaxy Evolution (SAGE; the ISM and stars) and the Herschel Inventory of the Agents of Galaxy Evolution (HERITAGE) surveys of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) focus on the lifecycle of dust. The LMC and SMC are ideal astrophysical laboratories for this study because their proximity to us permits detailed studies of the stars and their relation to the ISM from local to galaxy wide scales. For example, the masses of the circumstellar dust shells of stars and ISM dust clouds can be determined producing a more precise dust budget than possible for our own Milky Way galaxy. I will present key results from the SAGE and HERITAGE projects that quantify the stellar origin of dust, its evolution in the ISM and its consumption by star formation. Our measurements of dust mass-loss rates from entire populations of AGB and RSG stars and the discovery of ~0.5 solar masses of dust in the ejecta of supernova, SN1987A, provide the dust production rates by the stars. The maps of dust masses and gas-to-dust ratios of the ISM reveal how dust is destroyed and possibly created in the ISM. Our discovery of thousands of young stellar object candidates shows us locations of active star formation and enables us to quantify the star formation rate. I will end with a brief summary of the potential of the James Webb Space Telescope and/or the Origins Space Telescope to extend this research.