NED Abstract 
Copyright by American Astronomical Society.
Reproduced by permission

2007ApJ...656..818J

A Spitzer IRAC Census of the Asymptotic Giant Branch Populations in Local
Group Dwarfs. I. WLM 

Dale C. Jackson, Evan D. Skillman, Robert D. Gehrz, Elisha Polomski, and
Charles E. Woodward 

Abstract. We present Spitzer IRAC observations at 3.6 and 4.5 micron
along with optical data from the Local Group Galaxies Survey to
investigate the evolved stellar population of the Local Group dwarf
irregular galaxy WLM. These observations provide a nearly complete
census of the AGB stars. We find that 39% of the infrared-detected AGB
stars are not detected in the optical data, even though our 50%
completeness limit is 3 mag fainter than the red giant branch tip. An
additional 4% of the infrared-detected AGBs are misidentified in the
optical, presumably due to reddening by circumstellar dust. We also
compare our results with those of a narrowband optical carbon star
survey of WLM and find the latter study sensitive to only 18% of the
total AGB population. We detect objects with infrared fluxes consistent
with them being mass-losing AGB stars and derive a present-day total
mass-loss rate from the AGB stars of M^dot^=(0.7 --
2.4)x10^-3^M_sun_yr^-1^. The distributions of mass-loss rates and
bolometric luminosities of AGBs and red supergiants are very similar to
those in the LMC and SMC, and the empirical maximum mass-loss rate
observed in the LMC and SMC is in excellent agreement with our WLM
data. 

Key words: Galaxies: Dwarf, Galaxies: Individual: WLM, Galaxies:
Irregular, Galaxies: Local Group, Stars: AGB and Post-AGB, Stars:
Carbon, Stars: Mass Loss