The First Hyper-Luminous Infrared Galaxy Discovered by WISE

TL;DR

This paper reports the discovery of the first hyperluminous infrared galaxy by WISE, revealing a highly luminous, obscured galaxy with active galactic nucleus features at z=2.45, and introduces a new class of extremely luminous WISE sources.

Contribution

It presents the discovery and detailed analysis of WISE J181417.29+341224.9, the first hyperluminous infrared galaxy found by WISE, and characterizes a new population of extremely luminous WISE dropouts.

Findings

Minimum bolometric luminosity of 3.7 x 10^13 Lsun

Presence of an active galactic nucleus with high Eddington ratio

Dominant contribution of warm dust and starburst activity

Abstract

We report the discovery by the Wide-field Infrared Survey Explorer of the z = 2.452 source WISE J181417.29+341224.9, the first hyperluminous source found in the WISE survey. WISE 1814+3412 is also the prototype for an all-sky sample of ~1000 extremely luminous "W1W2-dropouts" (sources faint or undetected by WISE at 3.4 and 4.6 microns and well detected at 12 or 22 microns). The WISE data and a 350 micron detection give a minimum bolometric luminosity of 3.7 x 10^13 Lsun, with ~10^14 Lsun plausible. Followup images reveal four nearby sources: a QSO and two Lyman Break Galaxies (LBGs) at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission. Gravitational lensing is unlikely given the source locations and their different spectra and colors. The dominant LBG spectrum indicates a star formation rate ~300 Msun/yr, accounting for < 10% of the bolometric luminosity. Strong 22 micron emission relative to 350 microns implies that warm dust contributes significantly to the luminosity, while cooler dust normally associated with starbursts is constrained by an upper limit at 1.1 mm. Radio emission is ~10x above the far-infrared/radio correlation, indicating an active galactic nucleus is present. An obscured AGN combined with starburst and evolved stellar components can account for the observations. If the black hole mass follows the local M_BH-bulge mass relation, the implied Eddington ratio is >~4. WISE 1814+3412 may be a heavily obscured object where the peak AGN activity occurred prior to the peak era of star formation.