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

Enrichment of the Dust-to-Gas Mass Ratio in Bondi/Jeans Accretion/Cloud Systems

First Author:
Paul Bellan
Email: pbellan AT caltech.edu
Caltech
Mail Code 128-95
Pasadena, CA 91125 USA

Abstract

A cloud-accretion model has been developed having both an inner Bondi-type regime where gas pressure is balanced by the gravity of a star and an outer Jeans-type regime where gas pressure is balanced by gas self-gravity. High-velocity dust impinging on this cloud piles up due to having a different velocity profile than gas. This pile-up causes substantial enrichment of the dust-to-gas ratio above the 1% ISM level. An example where the dust-to-gas mass ratio is enriched to 20% will be presented (see ApJ 678, p.1099-1108, 2008).