THE MOST LUMINOUS GALAXIES DISCOVERED BY WISE

Abstract

We present 20 Wide-field Infrared Survey Explorer ( WISE )-selected galaxies with bolometric luminosities L bol > 10 14 L ☉ , including five with infrared luminosities L IR ≡ L (rest 8–1000 μ m) > 10 14 L ☉ . These "extremely luminous infrared galaxies," or ELIRGs, were discovered using the " W 1 W 2-dropout" selection criteria which requires marginal or non-detections at 3.4 and 4.6 μ m ( W 1 and W 2, respectively) but strong detections at 12 and 22 μ m in the WISE survey. Their spectral energy distributions are dominated by emission at rest-frame 4–10 μ m, suggesting that hot dust with T d ∼ 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 L bol level, corresponding to the most luminous unobscured quasars in the literature. We find that the rest-frame 5.8 and 7.8 μ m luminosities of the WISE -selected ELIRGs can be 30%–80% higher than that of the unobscured quasars. The existence of AGNs with L bol > 10 14 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 ∼10 3 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.