The Most Luminous Galaxies Discovered by WISE

Chao-Wei Tsai, Peter Eisenhardt, Jingwen Wu, Daniel Stern, Roberto Assef, Andrew Blain, Carrie Bridge, Dominic Benford, Roc Cutri, Roger Griffith, Thomas Jarrett, Carol Lonsdale, Frank Masci, Leonidas Moustakas, Sara Petty, Jack Sayers, S. Adam Stanford, Edward Wright, Lin Yan, David Leisawitz, Fengchuan Liu, Amy Mainzer, Ian McLean, Deborah Padgett, Michael Skrutskie, Christopher Gelino, Charles Beichman, Stéphanie Juneau

Published 2014-10-07Version 1

We present 20 WISE-selected galaxies with bolometric luminosities L_bol > 10^14 L_sun, including five with infrared luminosities L_IR = L(rest 8-1000 micron) > 10^14 L_sun. These "extremely luminous infrared galaxies," or ELIRGs, were discovered using the "W1W2-dropout" selection criteria (Eisenhardt et al. 2012) which requires marginal or non-detections at 3.4 and 4.6 micron (W1 and W2, respectively) but strong detections at 12 and 22 micron in the WISE survey. Their spectral energy distributions are dominated by emission at rest-frame 4-10 micron, suggesting that hot dust with T_d ~ 450K is responsible for the high luminosities. These galaxies are likely powered by highly obscured 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 micron luminosities of the WISE-selected ELIRGs can be 30%-80% higher than that of the unobscured quasars. Assuming Eddington-limited accretion, the existence of AGNs with L_bol > 10^14 L_sun at z > 3 places strong constraints on the supermassive black hole growth history, suggesting that these supermassive black holes are born with large mass, or have very rapid mass assembly, possibly by chaotic accretion.