EPICS: Evolution of Protostellar Ices comma Carbonates and Silicates

Dynamical and energetic processes that occur during the evolution of a protostar have a strong influence on composition and other characteristics of the dust and these can be well probed with farIR spectroscopy using Herschel.s PACS instrument. Physical evolution of protostars, driven by gravity, is accompanied by a dramatic evolution of the dust, driven by condensation and coagulation, thermal processing by the central star, and shocks driven by protostellar jets. MidIR spectroscopic studies of dust in protostellar environments reveal a wide diversity of dust components ranging from volatile ices, to carbonates to refractory crystalline silicates. However, the relationship between the dust evolution and the evolution of the protostar itself has not yet been studied. The evidence suggests that ices are connected to the deepest embedded phase, while crystalline silicates may trace the presence of disks. Carbonates may be either connected to processing of ices in the envelope of YSOs or result from disk processes. In order to probe this dust evolution that accompanies protostellar evolution, we have carefully selected a sample of wellcharacterized protostars spanning a wide range in evolutionary age and protostellar characteristics from the deeply embedded class 0 stage through the accretion disk (class I) and protoplanetary disk (class II) phases. We will employ PACS in SED mode to study the lattice vibration phonon modes of the ices, silicates and carbonates that occur in the 51 to 220 micron region. Our proposed study will allow us to address at what stage of protostellar evolution different dust signatures become apparent. In this way, we can address the (inter)relationship of these different compounds and the processes involved in their formation. Our study directly addresses Herschel.s toplevel goal of studying the ingredients in the dust throughout the evolution of a protostar that will then become pa tru [truncated!, Please see actual data for full text]