The Infrared Afterglow of Supermassive Black Hole Mergers
Abstract
We model the spectra and light curves of circumbinary accretion disks during the time after the central black holes merge. The most immediate effect of this merger is the dissipation of energy in the outer regions of the disk due to the gravitational wave energy and linear momentum flux released at merger. This has the effect of perturbing the gas in the disk, which then radiates the dissipated energy over a cooling timescale, giving a characteristic infrared signal for tens of thousands of years when the total black hole mass is M~108 Msun. On the basis of a simple cosmological merger model in which a typical supermassive black hole undergoes a few major mergers during its lifetime, we predict that ~104-105 of these IR sources should be observable today and discuss the possibility of identifying them with multi-wavelength surveys such as SWIRE/XMM-LSS/XBootes and COSMOS.