2020/12/17 by James M. Schombert, James Schombert, Stacy McGaugh · 7 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Asymptotic giant branch #Brightness #Galaxies: Formation, Evolution, Phenomena #Galaxy #Metallicity #Physics #Population #Red-giant branch #Star formation #Stars #Stellar, planetary, and galactic studies #Surface brightness #astro-ph.GA
paper · pdf · doi:10.3847/1538-3881/abd54d
published in The Astronomical Journal 161(2), 91 (Institute of Physics) · 29 pages, 11 figures, accepted by AJ
arxiv created 2020/12/17 · openalex created_date 2021/01/05 · openalex publication_date 2021/01/28 · arxiv updated 2021/03/17 · openalex updated_date 2026/08/05
Abstract We present new Hubble Space Telescope WFC3 near-IR observations of the color–magnitude diagrams (CMDs) in two low-surface-brightness galaxies, F575-3 and F615-1, notable for having no current star formation based on a lack of H α emission. Key features of the near-IR CMDs are resolved, such as the red giant branch (RGB), the asymptotic giant branch (AGB) region, and the top of the blue main sequence. F575-3 has the bluest RGB of any CMD in the literature, indicating an extremely low mean metallicity. F615-1 has unusually wide RGB and AGB sequences, suggesting multiple episodes of star formation from metal-poor gas, and possibly infalling material. Both galaxies have an unusual population of stars to the red of the RGB and lower in luminosity than typical AGB stars. These stars have normal optical colors but abnormal near-IR colors. We suggest that this population of stars might be analogous to local peculiar stars like Be stars with strong near-IR excesses owing to a surrounding disk of hot gas.