Mass Accretion Rates in Self-regulated Disks of T Tauri Stars

We have studied numerically the evolution of protostellar disks around intermediate and upper mass T Tauri stars (0.25 M⊙ < M∗ < 3.0 M⊙) that have formed self-consistently from the collapse of molecular cloud cores. In the T Tauri phase, disks settle into a self-regulated state, with low-amplitude nonaxisymmetric density perturbations persisting for at least several million years. Our main finding is that the global effect of gravitational torques due to these perturbations is to produce disk accretion rates that are of the correct magnitude to explain observed accretion onto T Tauri stars. Our models yield a correlation between accretion rate Ṁ and stellar mass M∗ that has a best fit Ṁ ∝ M ∗ , in good agreement with recent observations. We also predict a near-linear correlation between the disk accretion rate and the disk mass. Subject headings: accretion, accretion disks — hydrodynamics — instabilities — ISM: clouds — stars: formation