Dusty Stellar Birth and Death in the Metal-poor Galaxy NGC 6822

2020/02/27 by Alec S. Hirschauer, Laurin Gray, Margaret Meixner +4
Physics and Astronomy · #Astronomy and Astrophysical Research #Asymptotic giant branch #Galaxies: Formation, Evolution, Phenomena #Galaxy #Metallicity #Photometry (optics) #Red supergiant #Spitzer Space Telescope #Star cluster #Star formation #Stars #Stellar population #Stellar, planetary, and galactic studies #astro-ph.GA

paper · pdf · doi:10.3847/1538-4357/ab7b60

Accepted for publication in The Astrophysical Journal; 27 pages, 13 figures, 12 tables (master catalog will be available from publisher)

arxiv created 2020/02/27 · openalex created_date 2020/03/06 · openalex publication_date 2020/04/01 · arxiv updated 2020/04/08 · openalex updated_date 2026/08/05

Abstract

Abstract The nearby (∼500 kpc) metal-poor ([Fe/H] ≈ –1.2; Z ≈ 30% Z ⊙ ) star-forming galaxy NGC 6822 has a metallicity similar to systems at the epoch of peak star formation. Through identification and study of dusty and dust-producing stars, it is therefore a useful laboratory to shed light on the dust life cycle in the early universe. We present a catalog of sources combining near- and mid-IR photometry from the United Kingdom Infrared Telescope ( J , H , and K ) and the Spitzer Space Telescope (IRAC 3.6, 4.5, 5.8, and 8.0 μ m and MIPS 24 μ m). This catalog is employed to identify dusty and evolved stars in NGC 6822 utilizing three color–magnitude diagrams (CMDs). With diagnostic CMDs covering a wavelength range spanning the near- and mid-IR, we develop color cuts using kernel density estimate (KDE) techniques to identify dust-producing evolved stars, including red supergiant (RSG) and thermally pulsing asymptotic giant branch (TP-AGB) star candidates. In total, we report 1292 RSG candidates, 1050 oxygen-rich AGB star candidates, and 560 carbon-rich AGB star candidates with high confidence in NGC 6822. Our analysis of the AGB stars suggests a robust population inhabiting the central stellar bar of the galaxy, with a measured global stellar metallicity of [Fe/H] = −1.286 ± 0.095, consistent with previous studies. In addition, we identify 277 young stellar object (YSO) candidates. The detection of a large number of YSO candidates within a centrally located, compact cluster reveals the existence of an embedded, high-mass star formation region that has eluded previous detailed study. Spitzer I appears to be younger and more active than the other prominent star-forming regions in the galaxy.

Citations

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