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"SAGE-Spectroscopy: The life cycle of dust and gas in the Large Magellanic Cloud"
Principal Investigator: Alexander Tielens (NASA Ames Research Center)
Total Observatory Time: 224.4 hours
Cycling of matter between the ISM and stars drives the evolution of a galaxy's
visible matter and its emission characteristics. To understand this recycling,
the SAGE legacy project has surveyed the Large Magellanic Cloud with IRAC and
MIPS to study the physical processes of the ISM, the formation of new stars and
the injection of mass by evolved stars and their relationships on the
galaxy-wide scale. Due to its proximity, favorable viewing angle, and
multi-wavelength information, the LMC is uniquely suited to survey the agents of
a galaxy's evolution, the ISM and stars. We propose to leverage the SAGE legacy
program to conduct a comprehensive IRS and MIPS-SED spectroscopy program of dust
with the goal to determine the composition, origin, evolution, and observational
characteristics of interstellar dust and its role in the LMC. Analysis of the
spectra will yield composition and abundance of the dust compounds in different
LMC objects, including AGB stars, post-AGB, young stellar objects, HII regions
and the general diffuse ISM and provide a quantitative picture of the dust
lifecyle. Besides dust features, the spectra will also contain molecular and
atomic emission and absorption lines, providing the diagnostics to determine
physical parameters such as temperature, density and radiation field - all
important to the formation and processing of dust, and understanding the life
cycle of matter. The proposed spectroscopic survey will provide critical
underpinning for the SAGE survey by linking observed IRAC and MIPS colors of LMC
objects to the infrared spectral type of the object. We will to the maximum
extent utilize the LMC spectroscopy available in the Spitzer archive. A subset
of the IRS point sources from this proposal will also be surveyed in MIPS SED.
Legacy data products that will be made available to the public include all
reduced single point spectra and data cubes, feature maps, a spectral catalog,
and a fully classified SAGE point source catalog.
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