Selfgravity and QSO Accretion Disks

Princeton University, Princeton NJ

Investigators

Abstract

AST-0307558 Goodman The goal of this project is a dynamically self-consistent model for accretion in quasars. The outer parts of quasar accretion disks are prone to gravitational instability, and the problem is to explain why the gaseous disk does not fragment entirely into stars rather than feed the quasar. Some fraction of the gas may form stars or small black holes and heat the disk, postponing further fragmentation, but the energy required to stabilize large disks is probably more than can be made available this way. Preliminary calculations by the PI and students suggest that local heating can maintain marginal stability, and this work will further investigate this effect and its possible sources, as well as explore alternative (faster) accretion modes that could yield greater gravitational stability. Predictions from this partly analytical but mostly numerical work will be tested against observations, and the comparisons will feed back into the modeling. A combination of energy inputs and alternative rapid accretion may be required. The project will train graduate students in research and in the communication of their results by publication and by conference and institutional presentations. Pedagogical accounts of super-massive black holes, orbital motions, accretion, and other concepts related to this research, will be used to capture the interest of schoolchildren.