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. |