Other
Scientific paper
Mar 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008sptz.prop50167c&link_type=abstract
Spitzer Proposal ID #50167
Other
Scientific paper
It is both surprising and exciting to find that young galaxies at high redshift contain large dust masses. For galaxies at z>5, after only 1 Gyr, there has not been time for low-mass stars to have evolved to the AGB phase and produce dust. In such galaxies, Type II SNe and red supergiants (RSGs) may even dominate the dust production rate. It has long been known that RSG atmospheres produce dust, but little is known about it. So we are pursuing three parallel studies to better understand RSG dust. First, we are using optical spectra and JHK photometry to characterize the optical and near-IR extinction curves of the RSGs. Second, we are using the optical spectra combined with the 2MASS, IRAC and MIPS photometry to estimate the dust mass loss rates from Local Group RSGs as part of our archive program. In addition, we will use our Monte Carlo radiative transfer models to analyze the emission from dust in the circumstellar shells. Third, the final piece of the puzzle will be provided by obtaining new IRS spectra of LMC and SMC RSGs. We plan to use the IRS to make a systematic study of the dust properties in RSG shells in the LMC and SMC so that we can probe how they may vary with a large range of galactic metallicities. The intrinsic parameters of these stars have been well determined and, unlike Milky Way RSGs, their distances are well known. The existence of this precision dataset along with the availability of the high-sensitivity IRS on Spitzer will give us a unique opportunity to study the properties of dust in a large sample of RSGs. The new IRS spectra will be examined for emission features of PAHs, amorphous and crystalline silicates, and other materials, representing C-rich and O-rich dust dust produced around the star. The derived stellar SEDs and extinction curves will be combined with the IRAC and MIPS photometry and IRS spectra for use as inputs to our Monte Carlo codes which will be used to study the composition, size distributions and clumpiness of the dust.
Clayton Geoffrey
Ercolano Barbara
Gordon Karl
Levesque Emily
Massey Phil
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