Other
Scientific paper
Mar 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008sptz.prop50141s&link_type=abstract
Spitzer Proposal ID #50141
Other
Scientific paper
Through a combination of GO and GTO programs, we have obtained IRAC and MIPS imaging of 15 gas-rich Local Group dwarf galaxies. These data have allowed us to produce a complete census of asymptotic giant branch (AGB) stars in these galaxies and to measure the strength and spatial distribution of polycyclic aromatic hydrocarbon (PAH)s, warm dust, and cold dust emission. We have also identified the most extreme mass-losing AGB stars in the same 15 galaxies. The IRAC and MIPS data sets are complementary to each other, but the factor of three gap in wavelength between 8 and 24 microns leaves considerable uncertainty in the AGB and ISM spectral energy distributions (SEDs). We propose to complete the SEDs with IRS peak-up imaging at 16 microns, a wavelength that is crucial for understanding the PAH and small grain contribution to ISM dust and for determining the characteristics of AGB circumstellar dust and AGB mass-loss rates. Since the galaxies in our sample span over 1 dex in metallicity, the proposed observations will enable us to better study both AGB mass loss and PAH and small grain emission as a function of metallicity at very low metal abundance. Because the low metallicity environments of these dwarf galaxies are similar to those of galaxies at high redshift, these observations will help us to better interpret observations of high redshift star formation and dust production. Similar observations are not currently possible with any facility other than Spitzer and will not be possible with any planned future infrared missions, making Spitzer cycle-5 the final opportunity to fill this gap in our knowledge. These observations will be the only complete near- to far-infrared observations of resolved dwarf galaxies for considerable time into the future, and the resulting database will leave a valuable Spitzer legacy.
Boyer Martha L.
Boyer Martha
Cannon John M.
Gehrz Robert D.
Skillman Evan
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