Mass-loss from evolved stars: recent advances and future prospects
Speaker: Dr. Scicluna, Peter
Institute of Astronomy and Astrophysics, Academia Sinica
Time: 15:30pm 4th May, 2018 (Friday)
Venue: R521, IoA, 2nd General Building 綜二館R521
Evolved stars drive the chemical enrichment of the interstellar medium (ISM), creating new elements in their cores and fresh dust in their winds. Population models dictate that low- to intermediate-mass asymptotic giant branch (AGB) stars dominate this process today, while in the early universe, massive stars and supernovae were likely the main contributors. However, many key issues regarding AGB mass loss remain unresolved, including the total mass returned to the ISM by these stars, the physics driving the onset of mass loss, the fraction of the ejected mass that condenses into dust, and the role of variations in the mass-loss rate over time. I will review recent studies of AGB stars in the Milky Way and Magellanic clouds, which have revealed numerous insights into the mass-loss process and dust formation. I will conclude by introducing the Nearby Evolved Stars Survey (NESS), which is observing a volume-limited sample of ~400 mass-losing evolved stars. NESS is a growing collaboration of the East Asian evolved stars community in Taiwan, China, Japan, Korea and Vietnam, as well as collaborators in Europe and North America; scientists from East Asia are welcome to join at any time. Our purpose is to systematically derive the present-day gas and dust mass-loss rates and the mass-loss history of these objects using a coherent observing strategy across multiple observatories, including a JCMT large program. This will allow us, for the first time, to determine the total gas mass return to the Solar Neighbourhood, providing key constraints on AGB mass loss. The data will provide the first direct measurement of a global dust-to-gas ratio for stellar ejecta, and improve on existing determinations of the Galactic dust-production rate. The large sample will provide unique statistical power to generate insights into mass return over a large parameter space, and will result in a public database of observations open to the entire community. The NESS database is poised to become the authoritative source for evolved-star studies in the next decade.