| Description |
Dust, ice, and gas evolve as they move from envelopes of forming stars
into circumstellar disks where they can become the main building
blocks of planets. Herschel-PACS is uniquely suited to trace this
evolution through broadband emission from dust, through specific
features of solids which reveal elemental composition and water
content, and through spectral bands of the main icy components. Both
atomic and molecular lines, in particular the O I, H2O and OH lines,
will be used to follow the gas, study the interchange between gas and
ice, and trace the oxygen budget. The gas and dust spectral features
are at the same time excellent probes of macroscopic parameters, such
as temperature, UV and X-ray fields, density and thermal structures
of envelopes and disks, and dynamical mixing processes.
Our sample covers sources with a range in
evolutionary state from embedded objects with massive envelopes to
weak-line T Tauri stars with dissipating disks, and with a range in
luminosity, spectral type, and dust characteristics. Both our high S/N
PACS full spectral range scans (complemented by Spitzer mid-IR
spectral scans) and our targeted, deep gas-phase line measurements
will have lasting archival value. |
