Near-Infrared Stellar Populations in the metal-poor, Dwarf irregular
  Galaxies Sextans A and Leo A
  We present JHK$_{s}$ 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 colour-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 (2-8 Gyr 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 Leo A and 101 stars in Sextans A
with a DPR $>10^{-11}$ $M_\odot \,{\rm yr}^{-1}$, 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 $\pm$ 1.8) $\times 10^{-9}$ $M_\odot \,{\rm
yr}^{-1}$ and (6.2 $\pm$ 0.2) $\times 10^{-7}$ $M_\odot \,{\rm yr}^{-1}$,
respectively. The majority of this dust is produced by a few very dusty evolved
stars, and does not vary strongly with metallicity.
