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| Paper: |
A Spitzer/IRAC Census of the Asymptotic Giant Branch Populations in the Local Group Dwarf WLM |
| Volume: |
378, Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes |
| Page: |
427 |
| Authors: |
Jackson, D.C.; Skillman, E.D.; Gehrz, R.D.; Polomski, E.; Woodward, Ch.E. |
| Abstract: |
We present Spitzer/IRAC observations at 3.6 and 4.5 μm 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 asymptotic giant branch (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 three magnitudes fainter than the tip of the red giant branch. An additional 4% of the infrared–detected AGB stars are misidentified as sub-TRGB red giants in the optical, presumably due to reddening by circumstellar dust. We also compare our results with those of a narrow-band 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 we derive a present-day total mass-loss rate from the AGB stars of dM/dt= 0.7–2.4×10−3 M⊙ yr−1. The distributions of mass-loss rates and bolometric luminosities of AGB stars 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. |
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