| Description |
We propose the first extensive, systematic survey of gas in
circumstellar disks over the critical transition from gas-rich
protoplanetary through to gas-poor debris system. The brightest
spectral lines from disks lie in the far-infrared and arise from
radii ~10-500 AU, where giant planets are expected to form.
Herschel is uniquely able to observe this wavelength regime with
the sensitivity to allow a large scale survey.
We will carry out a 2-phase PACS study, surveying the fine
structure lines of CII157um and OI63um in 274 objects,
and following up the brightest sources with observations of
H2O and OI145um. The gas mass sensitivity, a few 1e-5 Msun,
will be more than an order of magnitude lower than achieved by
ISO and Spitzer and expected for SOFIA. We will also measure
the dust continuum to an equivalent mass sensitivity. Team
members include experts in the modeling of disk structure,
chemistry, and radiative transfer necessary to interpret these
data.
We will observe nearby clusters in the age range 1-30Myr,
encompassing disk masses 1e-2 - 1e-5 Msun, and stellar
luminosity 1-100 Lsun. This covers the dominant epoch of
planet formation and the mass from protoplanetary through
to young debris disk. Furthermore our sample is chosen to
include a wide range of X-ray & UV flux, and SED shape, from
classical SED Class II, through transition disks with inner dust
holes, to disks with small IR excesses. With this extensive
dataset, our program will:
- Trace gas and dust in the planet formation region across an
extensive multivariate parameter space
- Provide the first definitive measurement of the gas dissipation
timescale in disks
- Study the evolutionary link between protoplanetary and debris
disks
- Investigate the extent and evolution of warm H2O in the
planet-forming regions of disks, with implications for the
volatile content of developing planets
- Provide an extensive database of disk observations and
models with long-lasting legacy value for followup observations |
