9. Analysis plan
Dust SED and SpectraThe mapping part of the program will provide for each sky position the dust SED over the 7 SIRTF bands. We will use an updated version of the Désert et al 1990 model to derive from the SEDs the following set of parameters: the minimum PAH size, their abundance, the hot continuum around the 3.3 micron PAH feature, the abundance of very small grains and the power-law index of their size distribution. By combining the 160 micron observations with the IRAS 100 micron observations we will determine the large grain temperature. We will be able to determine the equilibrium temperature of large grains at the full resolution of the 160 micron MIPS observations in the selected spots where we will get observations in the SED mode and in cold condensations where the contribution of very small grains at 70 micron is negligible. The second step of the SED interpretation will be based on models of the impact of physical processes acting on dust size distribution and emission properties. We already have expertise in such models.
ISM StructureWe will correlate the SIRTF and gas maps to identify structures in the SIRTF images and measure their specific SEDs. This combination of observations will be used to correlate the observed variations of SEDs with physical conditions in the gas and kinematic properties. The SIRTF sky images will be used to characterise statistically the structure of the infrared emission as a function of wavelength.
Young Stellar ObjectsThe SEDI catalogs will contain a variety of source types (e.g. galaxies, YSOs, field stars) which can be distinguished by combining the optical and SIRTF data. For stars, the optical photometry is crucial to obtain approximate spectral types, distances, and extinctions. This in turn will allow us to place the stellar objects on an HR diagram and compare with evolutionary PMS tracks. From this one estimates masses and ages.
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