Planting seeds for gravitational wave generators around active galactic nuclei
Advanced LIGO event GW150914 has been attributed to the coalescence of two black holes with masses more than double that of most known stellar black holes. Formation of such stellar black holes directly through supernova explosions requires massive, metal-deficient progenitors. This requirement and their nearly equal masses may not be compatible with its occurrence in the local Universe. I consider an alternative possibility which may lead to the robust production of binary black holes with masses up to a hundred solar masses in the proximity of active galactic nuclei (AGN's). I will describe some relevant mechanisms which are analogous to the astrophysics of planet formation. I will discuss the implications of this scenario in the context of structure and evolution of AGN disks including the cause of their super solar metallicity, duty cycle of their active phase, and the rapid growth of their central massive black holes.