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Published November 2012 | Published
Journal Article Open

Spectral Energy Distributions of Local Luminous and Ultraluminous Infrared Galaxies

Abstract

Luminous (LIRGs; log (L IR/L ☉) = 11.00-11.99) and ultraluminous infrared galaxies (ULIRGs; log (L_(IR)/L_☉) = 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_☉) = 11.14-12.57 from the flux-limited (f_(60 μm) > 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 (~0.3-2 μm), and a dominant FIR (~40-200 μm) thermal dust peak, where νL_ν(60 μm)/νL_ν(V) increases from ~2 to 30 with increasing L_(IR). When normalized at IRAS 60 μm, the largest range in the luminosity ratio, R(λ) ≡ log[νL_ν(λ)/νL_ν(60 μm)], observed over the full sample is seen in the hard X-rays (HX = 2-10 keV), where ΔR_(HX) = 3.73 (R_(HX) = -3.10). A small range is found in the radio (1.4 GHz), ΔR_(1.4 GHz) = 1.75, where the mean ratio is largest, (R__(1.4GHz) = -5.81). Total infrared luminosities, L_(IR)(8-1000 μm), 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 ~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_☉) = 10.79 ± 0.40. Star formation rates have been determined from the infrared (SFR_(IR) ~ 45 M_☉ yr^(–1)) and from the monochromatic UV luminosities (SFR_(UV) ~ 1.3 M_☉ 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.

Additional Information

© 2012 American Astronomical Society. Received 2011 October 1; accepted 2012 September 2; published 2012 November 1. V.U. thanks O. Ilbert and S. Arnouts for their help with using the Le PHARE code, C. J. Ma for his help with UH 2.2 m data acquisition and reduction, T.-T. Yuan for her help with various scientific and technical contributions, and C. W. K. Chiang for statistical consult and technical help with Figures 1 and 3. V.U. also extends appreciation toward the UH TAC for their generous support of this project in awarding telescope time on Mauna Kea, as well as Colin Aspin and the UH 2.2 m Telescope staff for their help and support in the acquisition of the ground-based optical photometry. This research has made use of the NASA/IPAC Extragalactic Database (NED) and IPAC Infrared Science Archive, which are operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication has also made use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. V.U. wishes to acknowledge funding support from the NASA Harriet G. Jenkins Predoctoral Fellowship Project and Giovanni Fazio via the Smithsonian Astrophysical Observatory Predoctoral Fellowship and JPL Contract/IRAC GTO Grant 1256790. This paper is dedicated to the memory of Michele Dufault, who led the effort to obtain accurate large aperature photometric optical and near-infrared data for our complete sample of objects, and whose early work was critical in our decision to publish this paper.

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August 19, 2023
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