An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS),
  I. Overview
  Nearby resolved dwarf galaxies provide excellent opportunities for studying
the dust-producing late stages of stellar evolution over a wide range of
metallicity (-2.7 < [Fe/H] < -1.0). Here, we describe DUSTiNGS (DUST in Nearby
Galaxies with Spitzer): a 3.6 and 4.5 micron post-cryogen Spitzer Space
Telescope imaging survey of 50 dwarf galaxies within 1.5 Mpc that is designed
to identify dust-producing Asymptotic Giant Branch (AGB) stars and massive
stars. The survey includes 37 dwarf spheroidal, 8 dwarf irregular, and 5
transition-type galaxies. This near-complete sample allows for the building of
statistics on these rare phases of stellar evolution over the full metallicity
range. The photometry is >75% complete at the tip of the Red Giant Branch for
all targeted galaxies, with the exception of the crowded inner regions of IC
10, NGC 185, and NGC 147. This photometric depth ensures that the majority of
the dust-producing stars, including the thermally-pulsing AGB stars, are
detected in each galaxy. The images map each galaxy to at least twice the
half-light radius to ensure that the entire evolved star population is included
and to facilitate the statistical subtraction of background and foreground
contamination, which is severe at these wavelengths. In this overview, we
describe the survey, the data products, and preliminary results. We show
evidence for the presence of dust-producing AGB stars in 8 of the targeted
galaxies, with metallicities as low as [Fe/H] = -1.9, suggesting that dust
production occurs even at low metallicity.
