The Most Luminous Galaxies Discovered by WISE
We present 20 Wide-field Infrared Survey Explorer (WISE)-selected galaxies with bolometric luminosities Lbol > 1014 L☉, including five with infrared luminosities LIR ≡ L(rest 8–1000 μm) > 1014 L☉. These "extremely luminous infrared galaxies," or ELIRGs, were discovered using the "W1W2-dropout" selection criteria which requires marginal or non-detections at 3.4 and 4.6 μm (W1 and W2, respectively) but strong detections at 12 and 22 μm in the WISE survey. Their spectral energy distributions are dominated by emission at rest-frame 4–10 μm, suggesting that hot dust with Td ∼ 450 K is responsible for the high luminosities. These galaxies are likely powered by highly obscured active galactic nuclei (AGNs), and there is no evidence suggesting these systems are beamed or lensed. We compare this WISE-selected sample with 116 optically selected quasars that reach the same Lbol level, corresponding to the most luminous unobscured quasars in the literature. We find that the rest-frame 5.8 and 7.8 μm luminosities of the WISE-selected ELIRGs can be 30%–80% higher than that of the unobscured quasars. The existence of AGNs with Lbol > 1014 L☉ at z > 3 suggests that these supermassive black holes are born with large mass, or have very rapid mass assembly. For black hole seed masses ∼103 M☉, either sustained super-Eddington accretion is needed, or the radiative efficiency must be <15%, implying a black hole with slow spin, possibly due to chaotic accretion.
Additional Information© 2015 The American Astronomical Society. Received 2014 October 6; accepted 2015 March 4; published 2015 May 22. The authors thank the anonymous referee for the constructive comments and for encouraging a more thorough discussion of gravitational lensing in this paper. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. This work is also based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. Part of this research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Infrared Science Archive and the NASA/IPAC Extragalactic Database (NED), which are operated by the Jet Propulsion Laboratory, California Institute of Technology, under contracts with the National Aeronautics and Space Administration. This material is based upon work supported by the National Aeronautics and Space Administration under Proposal No. 13-ADAP13-0092 issued through the Astrophysics Data Analysis Program. C.-W. T. was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by Oak Ridge Associated Universities through a contract with NASA. R. J. A. was supported by Gemini-CONICYT grant number 32120009. Facilities: WISE, Spitzer (IRAC), Herschel (PACS, SPIRE), Keck:II (NIRC2)
Published - 0004-637X_805_2_90.pdf
Submitted - 1410.1751v2.pdf