An integral field spectroscopic study of ultraluminous and luminous infrared galaxies

Abstract

This dissertation presents an integral field spectroscopic study of 27 nearby ultraluminous and luminous infrared galaxies (U/LIRGs) from the Great Observatory All-sky LIRG Survey, a subset of the Revised Bright Galaxy Sample. The aim of these observations is to study the detailed and complex evolutionary processes affecting local U/LIRGs and to provide context for galaxy growth and evolution in the early universe, where U/LIRGs play a prominent role. The resolved spectroscopic data presented in this dissertation are analyzed with IDL spectral fitting routines which focus primarily on determining the detailed properties of the emission line gas. The resulting information obtained from the spectral fits are used to map the kinematics of the stars and gas, sources of ionizing radiation and feedback present in each galaxy. The resulting properties are tracked as a function of merger stage and parent galaxy properties. As a result of this analysis, we have found evidence for widespread, extended shock excitation in many local U/LIRGs. These low-velocity shocks become an increasingly important component of the optical spectra of our sample as the galaxies progress through major mergers. These results are also compared with mid and far-infrared diagnostics of dust and molecular gas to investigate the impact of these shocks on the ISMat multiple wavelengths. These results provide important context for ongoing observations of galaxies in the early universe. Also presented is an analysis of the metallicity gradients derived from 12 galaxies from the observational sample. The results trace the flattening of the metallicity gradient during a major merger as tidal effects and gas flows redistribute metals. The results from this analysis confirm previous theory and observation and inform new theoretical models of galaxy mergers and chemical enrichment.