Spitzer Space Telescope - Directors Discretionary Time Proposal #241


Dust to Dust:  A Study of Second-Generation Debris in
Scorpius-Centaurus

Principal Investigator: Christine  Chen
           Institution: NOAO

Science Category: circumstellar/debris disks 
 Observing Modes: IrsStare MipsSed 
  Hours Approved: 10.0 

Abstract:
Planets, asteroids, and comets are believed to form in circumstellar
disks of gas and dust with ages <100  Myr.  Although these objects are
not detected directly in disks, their presence can be inferred from
observations of spatial structure (e.g.  gaps, central clearings, and
warps) and transient gas phase molecules and atoms.  I plan to carry
out a multi-wavelength study of 5 - 20  Myr old F-, G-, and K-type
stars in the nearest OB Association, Scorpius-Centaurus, to search for
these signposts of Solar System body formation and to study the
evolution of solids from instellar dust grains to parent bodies.  I am
leading an effort by Spitzer GTO Mike Jura to search for dusty disks
around ~120  solar-like stars in Sco-Cen using MIPS at 24 micron and
70  micron.  Our first observations from this program have discoved
more than a dozen objects with fractional infrared luminosities as
high as 1.0e-3 (Chen et al.  2005).  Follow-up Spitzer IRS data,
obtained in collaboration with the IRS Disks team, will be combined
with Spitzer MIPS SED mode observations to determine the composition
of dust grains in these systems.  High resolution ground-based,
mid-infrared imaging in N- and Q-band will directly constrain the
location of warm dust grains and, when compared with high resolution
scattered light imaging, may help determine the grain albedo and
whether snow lines exist in these systems.  High resolution visual
spectroscopy will allow us to search for circumstellar gas, which may
either be remnant gas, left over from the formation of the system, or
secondary-gas, generated by the sublimation of infalling cometesimals.