THE DECOMPOSITION OF DUSTY GALAXY SPECTRAL ENERGY DISTRIBUTIONS

This thesis presents a new multi-component spectral energy distribution (SED) decomposition method for analyzing the ultraviolet to millimeter wavelength SEDs of dusty infrared-luminous galaxies. SEDs are constructed from spectroscopic and photometric data obtained with the Spitzer Space Telescope in conjunction with photometry from the literature. Each SED is decomposed into emission from populations of stars, an AGN accretion disk, PAH molecules, atomic and molecular lines, and distributions of graphite and silicate grains. Decompositions of the SEDs of 20 template starburst galaxies and 10 template AGNs provide baseline properties to aid in quantifying the star-formation and accretion contributions in composite sources. As case studies, we show that obscured radiation from stars is capable of powering the total dust emission from the composite galaxy NGC 6240, while the decomposition of Mrk 1014 is consistent with 65 % of its power emerging from an AGN and 35 % from star-formation. The properties of our template starburst galaxies and AGNs are used to estimate the AGN-strengths for some of our 75 ULIRGs, although many are so obscured that uncovering thei