Tiergartenstr. 15, D-69121 Heidelberg
e-mail: richling@ita.uni-heidelberg.de
2Jet Propulsion Laboratory, California Institute of Technology
MS 169-506, 4800 Oak Grove Drive, Pasadena, CA 91109
e-mail: Harold.Yorke@jpl.nasa.gov
Abstract:
We investigate the interaction of an external UV radiation field with
protostellar disks of low-mass stars using 2D radiation hydrodynamical
simulations. The disks are gradually destroyed via photoevaporation
as the UV photons heat the gas in the outer layers of a disk to thermal
escape velocities. Beside the UV flux and the luminosity of the
stellar wind from the central star, the evolutionary state of the
star-disk system at the onset of the external illumination determines
the size and the form of the ionized envelope and the resulting
spectral appearance of the object. Disks irradiated before one
free-fall time after the collapse of the parental molecular cloud lose
much of the associated material during the first 104yr of
evolution. The star-disk systems remain extremely small in comparison
to star-disk systems first irradiated at later evolutionary phases, where
the central objects are more massive and much of the clouds mass is
already bound in the accretion disk. These results suggest that an
early UV illumination favors the formation of low-mass cluster
members.
