Feedback‐driven Evolution of the Far‐Infrared Spectral Energy Distributions of Luminous and Ultraluminous Infrared Galaxies

We calculate infrared spectral energy distributions (SEDs) from simulationsof major galaxy mergers and study the effect of AGN and starburst drivenfeedback on the evolution of the SED as a function of time. We use aself-consistent three-dimensional radiative equilibrium code to calculate theemergent SEDs and to make images. To facilitate a simple description of ourfindings, we describe our results in reference to an approximate analyticsolution for the far-IR SED. We focus mainly on the luminous infrared galaxy(LIRG) and ultraluminous infrared galaxy (ULIRG) phases of evolution. Wecontrast the SEDs of simulations performed with AGN feedback to simulationsperformed with starburst driven wind feedback. We find that the feedbackprocesses critically determine the evolution of the SED. Changing the source ofillumination (whether stellar or AGN) has virtually no impact on thereprocessed far-infrared SED. We find that AGN feedback is particularlyeffective at dispersing gas and rapidly injecting energy into the ISM. Theobservational signature of such powerful feedback is a warm SED. In general,simulations performed with starburst driven winds have colder spectra andreprocess more of their emission into the infrared, resulting in higherinfrared to bolometric luminosities compared to (otherwise equivalent)simulations performed with AGN feedback. We depict our results in IRAS bands,as well as in Spitzer's MIPS bands, and in Herschel's PACS bands.Comment: Accepted to ApJ, 11 figures, 26 pages, added 2 figure