DUSTiNGS. III. DISTRIBUTION of INTERMEDIATE-AGE and OLD STELLAR POPULATIONS in DISKS and OUTER EXTREMITIES of DWARF GALAXIES

Kristen B W McQuinn, Martha L. Boyer, Mallory B. Mitchell, Evan D. Skillman, R. D. Gehrz, Martin A T Groenewegen, Iain McDonald, G. C. Sloan, Jacco Th Van Loon, Patricia A. Whitelock, Albert A. Zijlstra

    Research output: Contribution to journalArticlepeer-review

    16 Scopus citations

    Abstract

    We have traced the spatial distributions of intermediate-age and old stars in nine dwarf galaxies in the distant parts of the Local Group, using multi-epoch 3.6 and 4.5 μm data from the DUST in Nearby Galaxies with Spitzer (DUSTiNGS) survey. Using complementary optical imaging from the Hubble Space Telescope, we identify the tip of the red giant branch (TRGB) in the 3.6 μm photometry, separating thermally pulsating asymptotic giant branch stars from the larger red giant branch populations. Unlike the constant TRGB in the I band, at 3.6 μm, the TRGB magnitude varies by ∼0.7 mag, making it unreliable as a distance indicator. The intermediate-age and old stars are well mixed in two-thirds of the sample, with no evidence of a gradient in the ratio of the intermediate-age to old stellar populations outside the central ∼1′-2′. Variable AGB stars are detected in the outer extremities of the galaxies, indicating that chemical enrichment from these dust-producing stars may occur in the outer regions of galaxies with some frequency. Theories of structure formation in dwarf galaxies must account for the lack of radial gradients in intermediate-age populations and the presence of these stars in the outer extremities of dwarfs. Finally, we identify unique features in individual galaxies, such as extended tidal features in Sex A and Sag DIG and a central concentration of AGB stars in the inner regions of NGC 185 and NGC 147.

    Original languageEnglish (US)
    Article number78
    JournalAstrophysical Journal
    Volume834
    Issue number1
    DOIs
    StatePublished - Jan 1 2017

    Bibliographical note

    Funding Information:
    This work is supported by Spitzer via grant GO80063 and by the NASA Astrophysics Data Analysis Program grant number N3-ADAP13-0058. R.D.G. was supported, in part, by the United States Air Force .

    Keywords

    • Local Group
    • galaxies: dwarf
    • galaxies: evolution
    • galaxies: fundamental parameters
    • galaxies: photometry
    • galaxies: stellar content

    Fingerprint Dive into the research topics of 'DUSTiNGS. III. DISTRIBUTION of INTERMEDIATE-AGE and OLD STELLAR POPULATIONS in DISKS and OUTER EXTREMITIES of DWARF GALAXIES'. Together they form a unique fingerprint.

    Cite this