New Light on Young Stars:
Spitzer's View of Circumstellar Disks

The Formation and Evolution of Protostellar Disks

First Author:
Shantanu Basu
Email: basu AT astro.uwo.ca
University of Western Ontario
Dept. of Physics and Astronomy
London, Ontario N6A 3K7, Canada
Coauthors:
Vorobyov, E. I., ICA, Saint Mary's University

Abstract

We have studied numerically the self-consistent formation (from cloud core collapse) and evolution of disks around young stellar objects. The global evolution of the disk is followed for several million years after its formation. Calculations of such large dynamic range in space and time are made possible by use of the thin-disk approximation, and are not yet possible using fully three-dimensional simulations. We find that the disk evolution has an initial burst phase of accretion, during which the disk accretion rate is usually low (10^-8-10^-7 Msun/yr) but is punctuated by brief bursts of high accretion rate (~ 10^-4 Msun/yr). Later on, during the T Tauri phase, the disks settle into a self-regulated state, with low-amplitude nonaxisymmetric density perturbations persisting for at least several million years. 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 T Tauri star accretion rates. Our models yields a correlation between accretion rate Mdot and stellar mass Mstar that has a best fit Mdot ∝ Mstar^1.7, in good agreement with a now widely-observed correlation.
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