SPECTRAL ENERGY DISTRIBUTIONS OF LOCAL LUMINOUS AND ULTRALUMINOUS INFRARED GALAXIES

Luminous (LIRGs; log (L-IR/L-circle dot) = 11.00-11.99) and ultraluminous infrared galaxies (ULIRGs; log (L-IR/L-circle dot) = 12.00-12.99) are the most extreme star-forming galaxies in the universe. The local (U)LIRGs provide a unique opportunity to study their multi-wavelength properties in detail for comparison with their more numerous counterparts at high redshifts. We present common large aperture photometry at radio through X-ray wavelengths and spectral energy distributions (SEDs) for a sample of 53 nearby (z < 0.083) LIRGs and 11 ULIRGs spanning log (L-IR/L-circle dot) = 11.14-12.57 from the flux-limited (f(60 mu m) > 5.24 Jy) Great Observatories All-sky LIRG Survey. The SEDs for all objects are similar in that they show a broad, thermal stellar peak (similar to 0.3-2 mu m), and a dominant FIR (similar to 40-200 mu m) thermal dust peak, where vL(v) (60 mu m)/vL(v) (V) increases from similar to 2 to 30 with increasing L-IR. When normalized at IRAS 60 mu m, the largest range in the luminosity ratio, R(lambda) = log[vL(v)(lambda)/vL(v) (60 mu m)], observed over the full sample is seen in the hard X-rays (HX = 2-10 keV), where Delta R-HX = 3.73 ((R) over bar (HX) = -3.10). A small range is found in the radio (1.4 GHz), Delta R-1.4 GHz = 1.75, where the mean ratio is largest, ((R) over bar (1.4 GHz) = -5.81). Total infrared luminosities, L-IR(8-1000 mu m), dust temperatures, and dust masses were computed from fitting thermal dust emission modified blackbodies to the mid-infrared (MIR) through submillimeter SEDs. The new results reflect an overall similar to 0.02 dex lower luminosity than the original IRAS values. Total stellar masses were computed by fitting stellar population synthesis models to the observed near-infrared (NIR) through ultraviolet (UV) SEDs. Mean stellar masses are found to be log(M-*/M-circle dot) = 10.79 +/- 0.40. Star formation rates have been determined from the infrared (SFRIR similar to 45M(circle dot) yr(-1)) and from the monochromatic UV luminosities (SFRUV similar to 1.3M(circle dot) yr(-1)), respectively. Multi-wavelength active galactic nucleus (AGN) indicators have be used to select putative AGNs: About 60% of the ULIRGs would have been classified as an AGN by at least one of the selection criteria.