Spitzer Space Telescope - General Observer Proposal #20807


Spitzer Imagery & Spectroscopy of Symbiotics with Extended Nebulosity.

Principal Investigator: Frederick Bruhweiler
           Institution: Catholic Univ. of America

Co-Investigators: 
Glenn Wahlgren, Univ. of Lund                                         
Mattias Eriksson, Univ. of Lund                                       
Ekaterina Verner, Catholic Univ. of America                           
Bruce McCollum, IPAC/Caltech                                          

Science Category: stellar populations 
 Observing Modes: IrsStare MipsPhot 
  Hours Approved: 22.4 

Abstract:
The interacting binaries known as symbiotics defy easy placement in
our picture of binary stellar evolution.  It is unresolved if these
objects are more akin to recurrent novae or nuclei of PNe.  Optical
and radio imagery reveal that many symbiotics have extended ionized
nebulosities stemming from recent and prior ourbursts.  We will use
Spitzer to obtain MIPS 24 and 70  micron imagery and IRS SH and LH
spectroscopy of seven (7) symbiotics showing nebulosity with extent
greater than 10".  Our combined spectroscopic and imaging program has
the following goals.  1.)From MIPS imagery, we will use the dust
emission to more fully delineate the enshrouding ejecta.  This will
sample ejecta near the symbiotic and also at much greater distances,
associated with older outbursts.  Morphological comparisons for
individual objects will give information on whether the nebulae are
analogous to nova shells or PN.  2.) From IRS spectra, we will
determine the characteristics of the dust through presence of
crystalline silicates and possibly other discrete dust features in the
spectrum.  3.) We will use this to ascertain the dust properties,
environment, and chemistry at time of dust formation.  This will
greatly expand our knowledge of how symbiotics contribute to dust and
elemental enrichment of the Galactic ISM.  We will use the high
ionization forbidden lines in IRS spectra and our photoionization
modeling to derive the SED and the nature of the hot ionizing source
in symbiotics.  We will further use photoionization modeling, plus
spectral data at other wavelengths, to derive reliable abundances both
in the high-ionization region and in the low-ionization emission
region giving rise to the rich Fe II spectrum typical of symbiotics.
Our three-pronged complementary investigation of mapping morphology,
characterizing the dust, and abundance analysis, provides an
unprecedented means to determine the physical processes in, and
evolutionary phases of, symbiotics.