| Description |
Understanding protostellar evolution is a necessary step toward
characterizing the factors which ultimately determine the properties
of emerging stars and their planetary systems. We propose PACS
imaging and spectroscopy of protostars identified in Spitzer surveys
of the Orion molecular cloud complex. This is the richest known
sample of protostars at a common distance within 450 pc of the Sun.
Deep PACS 70 and 160 micron imaging will be obtained for 283
protostars ranging in luminosity from 0.1 to 1000 Lsun and spanning
the Class 0, Class I and flat spectrum evolutionary phases. The high
sensitivity and angular resolution will enable us to measure
bolometric luminosities in crowded fields, removing potentially
significant contributions from external heating. In concert with
existing near-IR and Spitzer mid-IR images and spectra, the deep PACS
imaging will be used to determine the fundamental properties of the
protostellar envelopes and disks (properties such as envelope
structure, density and angular momentum, disk luminosity). PACS
spectroscopy of 37 protostars will be used to measure water vapor, OH
and O lines arising in the envelope, in the accretion shock onto the
central protostellar disk, and in outflows. These data will provide
an unparalleled view of the flow of material from the envelope onto
the disk, through the disk to the star, and away from the star in
outflows. The Orion molecular cloud complex contains an exceptionally
wide range of parental gas conditions (i.e. initial conditions) and
environments (from dense clusters to relatively isolated protostars).
By comparing the properties of protostars in different regions of
Orion clouds; we will assess the roles of initial conditions,
environment and feedback from outflows in guiding protostellar
evolution. These observations will produce a unique legacy dataset
for guiding and testing a theory of protostellar evolution. |
