RED GIANT DISK ENCOUNTERS - FOOD FOR QUASARS

We explore the role that red giants might play in the fueling and evol ution of active galactic nuclei (AGNs). Due to their large radii and t he low binding energy of the stellar envelope, giants are vulnerable t o envelope stripping from collisions with the accretion disk. Using hy drodynamic simulations, we show that such collisions will typically de posit a substantial fraction of the envelope mass into the disk on eac h passage. Repeated encounters will then lead to the complete destruct ion of the star save for the dense core. We estimate the rate of fuel supply by this mechanism using simple models for the AGN disk and cent ral stellar cluster. If the central stellar density is similar to 10(7 ) M. pc(-3), then stripping of giants could account for the activity o f typical AGNs provided that the accretion disk extends out to similar to 0.1 pc. For AGNs with smaller disks, or clusters of lower central density, giant stripping could supply gas enriched via stellar nucleos ynthesis to a disk replenished from some other source. We find that, f or typical parameters, this mechanism is able to supply important quan tities of gas to the disk at lower stellar densities than previously p roposed stellar fueling models for AGNs.