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Description
We present JHKs observations of the metal-poor ([Fe/H]{<}-1.40) dwarf-irregular galaxies, Leo A and Sextans A, obtained with the WIYN High-resolution Infrared Camera at Kitt Peak. Their near-IR stellar populations are characterized by using a combination of color-magnitude diagrams and by identifying long-period variable stars. We detected red giant and asymptotic giant branch stars, consistent with membership of the galaxy's intermediate-age populations (2-8Gyr old). Matching our data to broadband optical and mid-IR photometry, we determine luminosities, temperatures, and dust-production rates (DPR) for each star. We identify 32 stars in LeoA and 101 stars in Sextans A with a DPR>10^-11^M_{sun}_/yr, confirming that metal-poor stars can form substantial amounts of dust. We also find tentative evidence for oxygen-rich dust formation at low metallicity, contradicting previous models that suggest oxygen-rich dust production is inhibited in metal-poor environments. The total rates of dust injection into the interstellar medium of Leo A and Sextans A are (8.2+/-1.8)x10^-9^M_{sun}_/yr and (6.2+/-0.2)x10^-7^M_{sun}/yr, respectively. The majority of this dust is produced by a few very dusty evolved stars and does not vary strongly with metallicity.
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