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G. Clayton (Louisiana State University), D. Welch (McMaster University)
In the Galaxy, dust production is split between low-mass Asymptotic Giant Branch (AGB) stars and SNe. Over 50% of dust production in the Galaxy is from old stellar systems (AGB stars & Type Ia SNe). However, dust production in high-z galaxies is expected to be much different. Galaxies at very high redshift have been observed to contain abundant amounts of dust even though they are quite young. After only ~1 Gyr, there has not been time for many low-mass stars to form and evolve to the AGB. Using estimates for our galaxy, the timescale for injection of stardust into the ISM is 2.5 Gyr. Evidence from pre-solar dust grains implies that Type Ia SNe are also significant sources for interstellar dust in our galaxy. However, Type Ia SNe, like the AGB stars, are old star systems that may not have had time to evolve. Hence, dust production in high-z galaxies may fall mostly to the Type II SNe. However, the condensation of dust in SN ejecta is not well understood. One reason is that detection of newly formed dust in young SNe in nearby galaxies has been extremely rare.
So, in August 2004, we began a program with Gemini/GMOS to study dust formation in Type II SNe. We were able to obtain spectra, as well as VRI photometry, of 14 Type II SNe with ages of 200 to 650 days. Dust formation in the SNe ejecta is signalled by a sudden decrease in continuum brightness in the visible due to increased dust extinction. This is accompanied by the development of asymmetric blue-shifted emission line profiles, caused by dust forming in the ejecta, and preferentially extinguishing redshifted emission from material behind the SN. We will present some preliminary results from this study.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.