Mathematics – Probability
Scientific paper
Jun 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005sptz.prop20436l&link_type=abstract
Spitzer Proposal ID #20436
Mathematics
Probability
Scientific paper
Based on the silicate-graphite-PAHs interstellar grain model, we propose to model the dust IR emission from nearby galaxies obtained by Spitzer on a pixel-by-pixel basis. The dust, consisting of a mixture of silicate grains and carbonaceous grains (graphite and PAHs) and spanning a wide range of sizes from a few angstroms to a few micrometers, is heated by starlight with a range of intensities in each pixel. By fitting the IRAC, MIPS photometry and IRS spectroscopy of each pixel, we will be able (1) to determine the spatial distribution of dust, the spatial distribution of starlight intensity, and the regional variation of the PAH abundance and properties within a galaxy, (2) to see how the dust mass and the abundance and properties of the PAHs vary from galaxy to galaxy, and (3) to relate the dust mass and the PAH abundance and properties with environmental conditions and galaxy type. We will calculate the temperature probability distribution functions for small grains (neutral PAHs and charged PAHs; silicate and graphite grains smaller than 250 Angstrom), as well as the steady temperatures of large graphite and silicate grains, for a wide range of sizes, exposed to starlight of a wide range of intensities and of a wide range of spectral shapes. We will build a ``library'' of temperature probability distribution functions and model IR emission spectra for each grain species of each grain size, heated by each starlight intensity of each starlight spectrum. This ``library'' will be made available to the astronomical community on WWW at http://www.astro.princeton.edu/~draine/dust/dust.html. This ``library'' will be very useful for interpreting the IR emission data (particularly the PAH emission features) obtained by Spitzer for both Galactic and extragalactic objects.
Draine Bruce
Li Aigen
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