Near-infrared Stellar Populations in the Metal-poor, Dwarf Irregular Galaxies Sextans A and Leo A

Olivia C. Jones, Matthew T. Maclay, Martha L. Boyer, Margaret Meixner, Iain McDonald, Helen Meskhidze

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    Abstract

    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 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 (2-8 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⊙ 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 ± 1.8) × 10-9 M yr-01) and (6.2 ± 0.2)× 10-7 M yr-1, respectively. The majority of this dust is produced by a few very dusty evolved stars and does not vary strongly with metallicity.

    Original languageEnglish
    Article number117
    JournalAstrophysical Journal
    Volume854
    Issue number2
    DOIs
    Publication statusPublished - 16 Feb 2018

    Keywords

    • circumstellar matter
    • infrared: stars
    • stars: late-type
    • stars: mass-loss

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