A NuSTAR Survey of Nearby Ultraluminous Infrared Galaxies

Ultraluminous infrared galaxies (ULIRGs) are typically weak in the X-rays based on previous surveys of ULIRGs at energies below 10 keV. It is thought that the poor detection statistics is a result of either the low luminosity nature of their central engines or the purported Compton-thick columns that obscure their nuclei. This is consistent with the idea that ULIRGs are part of an evolutionary paradigm where gas-rich galaxies collide, rapidly form stars and feed a buried active nucleus. The nucleus then shines as an unobscured quasar once the obscuring material is removed through galactic-scale winds. The ULIRG phase occurs during the most obscured period when the central black hole is growing most rapidly. Taking advantage of NuSTAR's sensitivity at energies above 10 keV, we conducted a survey of nine of the nearest ULIRGs. Here, we present the results from our imaging and spectral analysis of these data.